Author Topic: 5-Pin Power Supply for Rhodes Janus Preamp - DIY  (Read 3569 times)

Offline sean

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5-Pin Power Supply for Rhodes Janus Preamp - DIY
« on: October 14, 2017, 09:28:21 PM »
I needed a 5-pin power supply for my Rhodes Janus Preamp.  I decided I wanted to build it myself.  Since I am a total nutcase, I built five of them.  I built them three different ways, tested each method thoroughly, and documented each method so that you can build one too.
   

Quote
See the latest update - The Smallest 5-Pin Power Supply:  http://ep-forum.com/smf/index.php?topic=9706.0


The Janus preamp requires a power supply that provides +15V and -15V.  The 5-pin XLR connector pinout is shown in Steve Woodyard's technotes (http://www.fenderrhodes.com/service/amp-diffs.html).

If you have one of these preamps, it should match one of these schematics:
Schematic for Janus preamp with sliders: http://www.fenderrhodes.com/org/ch11/fig11-1.jpg
Schematic for Janus preamp with sliders, version 2: http://www.fenderrhodes.com/pdf/late-mark1-suitcase-janus1.pdf
Schematic for Janus preamp with five knobs: http://www.fenderrhodes.com/pdf/late-mark2-suitcase.pdf

The versions of the preamp with sliders for tone control use only three LM1458 op-amp chips, so they probably draw very little current.  The op-amp chips will likely draw less than 10mA each.  When you add the current-hog LED indicators, the total preamp consumption is probably less than 60mA.  I have the Janus 5-knob preamplifier that is built with four NE5534 and two RC4558 op-amps, so it still only needs a tiny bit of current:  a total of 80mA.  That’s 40mA from the -15V side, and 40mA from the +15V side (as measured on my preamp).

So we need a power supply that provides both +15V and -15V outputs, and it only has to provide less than 100mA from each side of the supply.  We are about to go through a lot of hassle for three watts of power.

There are three very simple options for power supply construction:
1.  Plain-old batteries.
2.  A modern switching power supply.
3.  A traditional power supply with a transformer, diode rectifiers, smoothing capacitors, and linear voltage-regulator ICs.

I thought that option 3 was going to be the only way to go, but I was surprised to find that option 1 is by far the cheapest and works great, and that option 2 is perfectly quiet and easy to build.

________________________________________


Before I tell you how to build them, I want to tell why you should not do it.  You should buy the 5-pin power supply from Vintage Vibe for $219, and the 5-pin XLR cable for $65.  You get a professionally-constructed power supply that is painted beautifully, and includes a clip to hang it from the handle on the side of the piano.  It is fully-tested, durable, and reliable; and it is backed by the Vintage Vibe team.  If you are a gigging musician, it is certainly the right way to go. 

You can build the power supply yourself, but it takes a lot of time, and you don’t save much money.  I mean it:  you don’t save as much money as you think by building it yourself.  It also takes more time than you can believe.  Ordering all the parts, waiting for them to arrive, filing down the rough edges on the enclosure, marking and drilling holes in the enclosure, painting or polishing the enclosure, soldering the circuit together, testing it, installing it into the enclosure – it adds up to a lot of time.  If you have to buy any tools, then you will blow the budget.

So if you are a pro musician, get it pre-made from Vintage Vibe, RetroLinear, Avion Studios, or CAEsound.  If you are not, and you are good with a soldering iron and a drill press, and you know enough about electricity to be safe, you might want to make your own; so read on.

If you just got a Rhodes, and you don’t know if the preamp even works, build the battery supply in a cardboard box.  It is the cheapest and fastest to build, and great for testing. 

If you need a backup power supply for gigging or the studio, build one of the switching power supplies. 

If you have some bizarre romantic idea that a step-down transformer, diodes, filter capacitors, and voltage regulator chips will be best for you – think again and build one of the switching power supplies.


If you decide to build one, please read the all the other sections below to get all the tips and tricks that I may not have repeated in each section.

TL;DR – It is just simply too long.  Give up now. 
« Last Edit: December 12, 2017, 01:25:07 AM by sean »

Offline sean

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5-Pin Power Supply for Rhodes Janus Preamp - DIY
« Reply #1 on: October 14, 2017, 09:28:51 PM »

Helpful advice for all construction methods:
If you build your own power supply, there are three basic steps: buy all the components, prepare the metal box, then wire it up and fire it up.

Each section below includes a detailed shopping list.  All of the components are easy to find on the common electronics supply websites.  Mouser has a very broad variety of items that can be purchased in single one-at-a-time quantities.  Digikey seems to have the best website, but no free shipping.  Arrow’s website is hateful and slow, but they have fast free shipping and other promotions.  I haven’t tried Newark/Farnell/element14 yet.  Markertek has good prices on XLR connectors and free shipping.  Amazon is easy and sometimes fast, but does not provide manufacturer’s certificate of conformance (sources are questionable), and Amazon has many low-quality incompletely-described product listings.  I feel safe buying Bud boxes and XLR connectors from Amazon, but not integrated circuits, capacitors, batteries, nor transformers. 

There are a bunch of different brands of 5-pin XLR connectors available, and they all have a slightly different appearance and price tag.  Pick your favorite.  In the drawings below, the connector depicted is a face-swap between the old Switchcraft D5F and the Seetronic K5F2C, but it turns out to look exactly like the Switchcraft DE5F (lucky coincidence).  See the list of 5-pin XLR panel-mount and cable-end connectors at the bottom of this old post: http://ep-forum.com/smf/index.php?topic=9533.msg52502#msg52502

When you select a switch, don’t buy one with snap-in mounting tabs.  The snap-in mounting system works great if you have very precise holes with sharp square edges on the interior of the box.  If you use a snap-in mounted switch, do not de-burr, round off, or sand the inside edge of the mounting hole.  Since I don’t have a turret punch, I use a step drill to make large holes.  The holes are a bit irregular.  It is most reliable to use a switch that has threads and a nut.

You should buy a steel or aluminum box for your power supply.  There are PVC plastic boxes, but they don’t save you much money, and they will not last long, and they will never feel as good as a cast-aluminum box.  (There are plastic boxes made of polycarbonate, but that will blow your budget.)  I prefer the Bud EconoBox cast-aluminum boxes.  They aren’t as cheap as they used to be, and the bottom plates are a bit crudely cast and finished, but I still like them best. 

Take a look at Bud CU-247, CU-347, CU-452-A, CU-482-A, and CU-3008-A in the links below:
Bud Econoboxes:  http://www.budind.com/view/Die+Cast+Aluminum+Enclosure/Econobox
Bud sheet metal Miniboxes:  http://www.budind.com/view/Small+Metal+Electronics+Enclosures/Miniboxes
Bud Converta sheet aluminum boxes:  http://www.budind.com/view/Small+Metal+Electronics+Enclosures/Converta+Boxes
Bud metal chassis that requires you to purchase the bottom plate separately:  http://www.budind.com/view/Aluminum+Enclosure/Aluminum+Chassis


Hammond makes cast aluminum boxes too, but they have a less-rounded edge around the top.  I like the slightly gentler edges of the top on the Bud EconoBox series, but Hammond 1590 series or the 1550 series would be fine.  The bottom plates on the Hammond boxes seem to be more carefully finished, and they fit better without filing, grinding, and sanding.
See http://hammondmfg.com/dwg.htm and http://hammondmfg.com/1550.htm.


You might have an old small toolbox, tackle box, metal cash box, or a metal recipe box.  The Bud and Hammond boxes cost between $10 and $20, so a free box doesn’t save tons of money.  I can’t bear the thought of putting in all the effort to build the power supply just to wind up using a cheesy box.  You want to be proud of your work.

If you build your own power supply, you will have to build or buy a cable with five-pin XLRs, preferably with right-angle female end.  The right-angle connector is expensive – there are newer and cheaper right-angle XLR connectors, but they don’t look as nice (when compared to the Switchcraft R5F, or the Neutrik NC5FRX).  The XLR cable is plugged into the namerail, so you are staring at it every minute while you are playing.  I want a connector that looks sturdy and sleek, for me, nothing beats the Switchcraft R5F, and no store-bought cable comes with that. 

Again, see  http://ep-forum.com/smf/index.php?topic=9533.msg52502#msg52502 to make a cable for yourself, or to buy a cheap not-right-angle cable that works.

If you decide to build your own power supply, please read:
Tools you may need:  http://ep-forum.com/smf/index.php?topic=9657.msg53396#msg53396
Finish - Polish or Spray Paint:  http://ep-forum.com/smf/index.php?topic=9657.msg53397#msg53397

You must also read all of the other sections to find all the endless drivel tips and tricks that I might not have repeated in each section.

« Last Edit: October 19, 2017, 02:04:39 PM by sean »

Offline sean

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5-Pin Power Supply for Rhodes Janus Preamp - Build it with batteries
« Reply #2 on: October 14, 2017, 09:29:12 PM »
Method 1.  Build a +15V/-15V power supply with batteries.

Ten AA cells connected in series will give you 15V.  So all you need is twenty AA batteries, and a convenient way to mount them.  Mouser has ten-cell AA battery holders.  I like the 12BH310B-GR, because it has terminals that snap into a connector like on top of a 9V battery.  This way, you can easily remove the whole battery holder to replace the batteries, and then snap the whole block back in place.  Since the battery holders are only two bucks each, you can buy two extra to keep spare batteries pre-loaded and handy.

I haven’t needed to change the batteries yet - they last a long long time.  Even if you only get 1200mAh from the cells, it will run the preamp for 30 hours.  The battery pack that I put together has been run for a few hours (maybe four) over the last few months, and still measures more than 15V per side.  AAA batteries work too, but they might only last for 20 hours of playing (still pretty nice).  The battery box could be a good solution for home practice or maybe occasional rehearsals where you don't want to lug along the whole suitcase bottom, but I think it is better-suited to testing and experimenting at home. 

I built my first test unit just to see if my preamp worked.  I used what I had:  two holders for eight cells, and two holders for two cells.  I flopped them all into a cardboard box, pushed the connections into a little breadboard, rigged up a switch in a little jewelry box, and then plugged it in to the preamp using a test cable I made with a cheap 5-pin XLR female cable-end connector (Seetronic SC5FXX-B). 

If I were serious about using this as a long-term solution, I would look for a box that was easy to open to replace the batteries.  I think an old-fashioned kid’s metal lunch box would be perfect if I reinforced the area where the connectors would be mounted.  A tiny metal toolbox, fishing tackle box, metal cash box, or biscuit tin might be fine.  Build it with whatever you can find in the garage or basement.  Since there is no high voltage involved in the battery power supply, it is safe to build it into a plastic box or a cardboard box.  If you want to spend big money, you can buy a Fender Lunch Box (I didn’t know they existed, but they are fifteen bucks and look like a little amp).  If you want to spend only three bucks, get an empty quart paint can at your local hardware store.

This is what the construction would look like if you put it in an expensive box from Bud Industries.  Use this drawing as a guide for the construction and wiring, but don’t buy an expensive box for this battery project.

Wiring Diagram for PS built with AA batteries in two ten-cell holders: 




If you don’t have a ten-cell battery holder, you can build it with smaller battery holders.  The drawing below shows the wiring with the smaller battery holders daisy-chained together.  This is also how you are forced to build it using AAA batteries, because you won’t find a ten-cell battery holder for AAA batteries. 

Wiring Diagram for PS built with AAA batteries in four holders:




Here is the shopping list for building the 5-pin power supply with batteries:
20 each  AA batteries
2 each  ten-cell AA battery holder, Eagle Plastic Devices (EPD) 12BH310B-GR
         (get two extra battery holders to store extra batteries in the holders for convenience)
2 each  battery snap connecter, Keystone 237 or 237-M
1 each  box to put it in, metal lunchbox or biscuit tin (don’t buy the expensive Bud CU-347)
1 each  5-pin female XLR panel-mount connector, like Switchcraft DE5F, or Seetronic K5F2C
1 each  DPDT power switch (DPST are harder to find), like E-switch RR3130B
2 each  1/4” jacks, mono (just tip-shield), like Switchcraft 11 or L11
2 each  #4-40, 3/8” or 1/2” flat-head screws and nuts to mount the XLR connector
Assorted wire, shrink tubing, solder, and tools from your basement or garage.


The battery supply could save you a lot of money, but it might not be a great long-term solution. 

You should be able to buy the materials in the shopping list for under $36.00 plus shipping from two sellers – worst case $16.00 total shipping (and a trip to the hardware store).  It will cost a little more if you choose one of the expensive XLR connectors.  You might dig around and find a box for free, but you still have to buy or make the XLR cable.  You should keep an extra set of extra batteries handy, and every few weeks you will have to buy batteries again ($14 bucks a pop).  So your savings will evaporate.


Lessons learned from actually building two (one with AA, one with AAA):
The lunchbox turned out to be too flimsy.  It looks nice, but it will get dented and destroyed pretty easily.  I did not bother to reinforce the area around the connectors, so it isn’t going to last through a lot of cable insertions and removals.  A sturdier box is a better idea.

The step-drill did NOT work well in the thin metal walls of the lunchbox.  It didn’t cut so much as it stretched out the hole, and it left a huge jagged and sharp lip on the inside of the box.  I guess I was drilling with the speed set way too high.  I used dykes to snip away the sharp edges, but I should have used my mototool to clean it up instead.  The step drill created the ugliest holes I have ever created in a workpiece.  The step drill also created a lot of heat, so the paint around the holes got burnt (and smelled foul).

I had a small “tin” box set aside to use for the AAA-battery power supply; but after working with the thin-walled lunchbox, I instead chose a Bud CU-3006A Minibox.  It is cute, tiny, and durable enough to survive.  It does require a screwdriver to get inside and change the batteries.  After sanding down all the edges on the Minibox, it is more pleasant to handle, but I still worry that it might scratch a piano top or a wooden table top.

I used the Seetronic K5F2C XLR connector for the box with AAA batteries.  It has little positioning fins that require three notches around the perimeter of the mounting hole.  So the hole looks like this: 




I couldn’t find ten-cell AAA holders, so I had to split them up into an eight-cell and a two-cell holder.  I couldn’t find a two-cell AAA holder that had the battery snap terminals, so I got all the AAA holders with wire leads attached.  I reinforced the thin wires with shrink tubing.

Keeping the batteries from bouncing around inside the box is a bit of an issue, but since there is no high-voltage, you can stuff the box with bubblewrap or old socks.  The batteries can also be restrained by rubber bands, tape, or wire ties.  In the tiny box with the AAA batteries, I secured the batteries by filling the remaining space with Lego bricks.

The ends of the battery holders have the electrical contacts exposed (but not sticking out).  I used a layer of electrical tape to protect them. 

On these battery boxes, I used a very inexpensive DPST switch.  The cheap plastic switch bodies don’t seem to appreciate the heat from soldering.  The terminals moved when heated, and became looser than normal.  After soldering the first one, I switched to using slide-on terminals that are crimped to the wires.  The terminals on the switch were 3/16” wide by .032” thick (.81mm).  The terminals I had on hand were for terminals thinner than this, so I had to spread the contacts a bit.  This is not something I would do on a switch for high voltages.  I would not want to risk the terminals coming loose.  For the other power supplies, I used better-quality switches and ordered the correct connector terminals. 


The connectors in the lunchbox:



Lunchbox PS ready for AA batteries:



Lunchbox PS with batteries properly secured:



Guts of PS with AAA batteries:



Guts of PS with AAA batteries showing Lego bricks holding the batteries in place:


« Last Edit: October 16, 2017, 06:15:05 PM by sean »

Offline sean

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5-Pin Power Supply for Rhodes Janus Preamp - Build around Mean Well PD-2515
« Reply #3 on: October 14, 2017, 09:29:33 PM »
Method 2a.  Build around a Mean Well PD-2515 switching power supply.

This is much easier than I expected.  The PD-2515 from Mean Well provides both the +15V and -15V voltages in a tiny 4.2" x 2.4" x 1.1" little product.  It is dead quiet with my 5-pin Rhodes Janus 5-knob preamp.

The Mean Well PD-2515 provides up to 800mA, and works all over the world (AC input: 85-264V AC, 47-63 Hz).  See the PD-2515 spec sheet.  I bought my PD-2515 from Jameco for $11.25, and you can get them from Mouser, Sager, or Amazon for under $20.

You will need the correct Molex connectors to plug into the circuit-board headers on either end of the PD-2515.  The Molex connectors require a crimping tool to attach the connector terminals to the wires, and then insert the terminals into the connector housing.  You have to buy the connector housings, terminal pins, and crimp tool separately.

For AC power input, the PD-2515 has:
-   a three-position Molex 41791-0003 header; it mates with Molex 09-50-3031 connector housing.

For DC power output, the PD-2515 has:
-   a four-position Molex 41791-0004 header; it mates with Molex 09-50-3041 connector housing.

You will need to crimp Molex 08-50-0106 female terminal pins onto all your wires, and stuff them into the connector housings.  I used an IWISS SN-28B crimp tool.  Sadly, the crimp tool is $23.00 at the cheapest I can find it; but it is a beautiful tool.

The Molex connectors and pins are cheap, a total of three bucks for five of each housing and fifty pins.  It is nearly impossible to crimp the pins without the crimp tool, because a sloppy crimp makes it difficult to fit the pins into the connector.  For safety's sake, don't fool around with the connections that will carry 120V AC.  Get the crimp tool.

The crimp tool, pins, connector housings, and the Mean Well PD-2515:



This is the shopping list to build a 5-pin power supply with the Mean Well PD-2515:
1 each  Mean Well PD-2515 Power Supply
5 each  Molex 09-50-3031 connector housing (only need one, but get a few, they are cheap)
5 each  Molex 09-50-3041 connector housing (only need one, but get a few, they are cheap)
50 each Molex 08-50-0106 female terminal pins (okay, maybe only get twenty)
1 each  IWISS SN-28B crimp tool, or similar crimp tool
1 each  C14 power inlet connector, like Bulgin PX0580/28
1 each  C13 AC power cord stolen from your old computer
1 each  Bud CU-247 cast aluminum EconoBox, 7.4" x 4.7", 2.2" tall
1 each  Panel-mount 5-pin XLR connector, like Switchcraft DE5F or Seetronic K5F2C
2 each  Switchcraft 11 or L11 mono 1/4" jack
1 each  AC Power Switch, like Mountain 103-R13-135B-02R-EV, 103-R13-135A2-02-EV, 103-R13-135A-02-EV, or E-Switch RR3130ABLKBLKES.
3 each  Quick-disconnect female terminals for tabs on the switch, either Molex 19003-0017
or TE/AMP 2-520194-2, 3/16” wide, .032” thick (4.75mm x .81mm) – order a few extra
4 each  #4-40, 3/8” or 1/2” flat-head screws and nuts to mount the XLR connector and C14
4 each  #6-32, 3/4” or 1” flat-head screws and nuts to mount the PD-2515
4 each  Nylon spacers to mount the PD-2515, 1/4” tall, 3/8” diameter
Assorted wire, shrink tubing, solder, and tools from your basement or garage.


You will wind up spending more than $150.00 to assemble all the supplies and tools.

The items specifically in the shopping list will cost ninety bucks plus shipping from two suppliers (and a trip to the hardware store).  This includes the $23 crimper, but assumes that you got the AC power cord for free.  It will cost a little more if you buy an expensive XLR connector.  You should also buy a few bucks worth of heat-shrink tubing for insulating the connections at the AC power inlet and the switch (if you don’t use the insulated terminals). 

Spray paint costs money, and you will need a can of primer and a can of topcoat color.  You will have to buy some tools - the step drill and de-burring tool most likely.

Before you know it, you have spent well over one-hundred-and-fifty dollars, waited a few days for shipping, and you haven’t even starting building the thing.  That’s why I recommend that you buy the 5-pin power supply from Vintage Vibe or one of the other folks.


The diagram below shows the wiring connections and component locations for a 5-pin power supply built around the Mean Well PD-2515:




You might notice that I have omitted the 680Ω resistors on the audio outputs.  These resistors are shown as R1 and R2 in the schematics for the suitcase bottom – figures 11-3 and 11-4 in chapter 11 of the service manual.  These resistors would provide additional short-circuit protection and maybe some power-on thump protection (if you power up the amp after you plug it into the audio jacks on this power supply).  The preamp itself has 100Ω resistors on both outputs that would protect the op-amp outputs from short circuits, but maybe the power-on spikes are something I should worry about.  If you feel that the 680Ω resistors should be included, they would replace the wires going between the XLR connector and the tip connections of the1/4” jacks. 


It will take many more hours to drill and finish the enclosure than it will take to wire and solder the connections.  You can be sloppy with your wiring (because nobody will see it); but everybody will see the outside of the finished power supply, so it is worth taking your time and making it look sharp.

Think about where they want the power supply to sit or hang, and plan where you want the connectors located.  You may want the connectors on top of the power supply, or you may want them on opposite sides.  Pick a layout that makes you happy.  But make sure that you can fit all the internal components out of the way of the connectors.

My original plan was to have the connectors arranged as shown in the wiring diagrams.  After spending hours and hours creating the pretty drawings, I decided to put all the connectors on one side of the box.  That way, all the wires can lay flat on the floor neatly running away from the player and not underfoot.  I guess in a stage situation, this would put all the connectors facing the audience, or the box can be turned to run the cables out to the left side.

Here is a layout drawing that shows my hole placement on one side of the box:




When you measure and mark the hole locations for the connectors and the switch, make sure that you leave extra room near the corners for the lid-screw pillars (bulges) on the interior of the box.  The wiring diagram above shows approximate locations for all the holes and components, and the layout diagram shows exact locations if you want all the connectors on one side.

The switch and the XLR connector require nice round holes much larger than 3/4”.  I drilled small pilot holes to accurately locate the center, and then expanded the holes with a step drill.  The hole for the C14 AC-power inlet connector has to be carved out by hand.  Measure and mark a rectangle (or the hexagon shape), and then drill small holes along the inside of that marked shape.  Use a small file or a Mototool to grind away until the hole fits the connector.  Insert the connector and mark the holes for the mounting screws.  You will mount the XLR connector and C14 AC power inlet with #4-40 flat-head machine screws and nuts. 

To mount the PD-2515, you will use four 1/4” tall, 3/8” diameter nylon standoffs (spacers), four 3/4” #6-32 flat-head machine screws, and four #6-32 nuts.  Carefully mark the locations for the mounting holes on the bottom of the box.  I used the measurements from the spec sheet, but you could also sit the PD-2515 on the lid and very carefully transfer the hole locations with the scratch awl that is included in your combination square.  Mount the PD-2515 safely away from the edge of the box, so that it does not hit the mounting-hole pillar inside the top of the box when closed.

To mount the PD-2515, center-punch and then drill 1/8” diameter holes in the bottom lid (the #6 screws won’t fit in the 1/8” hole, but they will fit after you countersink the hole).  When you countersink the holes, be excruciatingly careful.  If you go too deep, you will ruin the box.  I got a little chatter with the drill press on 1720RPM, so 1100RPM or 620RPM is safer.  It is easy to get a very lopsided hole if you use the countersink in a hand drill – don’t let the hand drill spin fast.  Test-fit the hole frequently with the flat-head screw to make sure you are not drilling too deep.  Make the countersink just barely deep enough for the screw to sit flush.  Shallower is better than deeper.  I think this step is the most dangerous, in the sense that it is the easiest way to ruin the project.

When the PD-2515 and all the connectors test-fit well, you are ready to finish the surface of the box.  I prefer to sand and polish the Bud box, rather than paint it.  Painting should be easier, but paint is easy to ruin with lint or hair in the painting process and easy to scratch.  (To me, scratched paint looks worse than scratched bare polished metal.)  Either finishing method takes a lot of time.  See the finishing instructions in the Polish or Spray Paint section below.


Wiring and Construction:
The Molex connectors for the Mean Well PD-2515 simplify the assembly process.  If you mount the Mean Well PD-2515 on the bottom plate of the Bud CU-247, then you should make your wires to the connectors long enough to open the box, flip the bottom plate over, and lay everything down on the workbench so you can test and repair the assembly while the Molex connectors are plugged in.  Eight inches will work, and can be coiled up when the box is closed. 

If you buy a different enclosure (like the Bud CU-482-A or cheaper CU-3008-A), you should be able to mount all the components on the chassis and have nothing installed on the top lid.  It would still be nice to have a little extra length in the wires to each Molex connector, so that you can easily reach your hand in there and plug and unplug them when finally assembled. 

Crimp 22AWG wires onto the Molex terminal pins for the DC connections, and crimp 18AWG flexible multi-stranded wires onto terminals for the high-voltage AC connections. 

Notice how the little locking tabs on the white connector housings mate with the headers on the PD-2515.  Use this as a clue how to orient the connector housing when installed, so that you get your wires inserted into the right places.  Gently push the terminals into the connector housing until the metal tab on the terminal locks it into the connector housing.  If you can pull the wire out of the connector, either your wire is not tightly crimped into the terminal, or the terminal is not locked into the housing. 

If your switch doesn’t have the LED indicator (power on) light, then you don’t need the neutral wire connection to the switch.

All of the AC power connections to the inlet socket should be soldered and insulated with heat-shrink tubing.  The switch connections can be soldered or made using fully-insulated terminal lugs.  Slip the heat-shrink tubing over the wires before you solder the connections, and then shrink the tubing with a heat gun (fancy hair dryer).  You will notice in the diagram that I chose to leave the ground terminal from the AC power cord unconnected.  I decided that I didn’t want the household wiring ground connected to the audio ground and the chassis.

It is easiest to solder the wires to the XLR connector before it is mounted in the box.  Remember to insert two green wires into pin 1 – one for the ground connection to the circuit board, and one for the audio outputs.  Twist the stripped ends of two green wires together, then cut off the excess, and then solder them to pin 1. 


Lessons learned from actually building one:
Since the Bud box has sloped sides, when laid sideways for drilling, the top surface won’t be level.  You need to hold or clamp the workpiece at an angle so that the top surface is level.  This way, the drill will be perpendicular to the surface being drilled.  Be very careful, because all it takes is a small mistake to ruin a $20 Bud box.  Always wear eye protection when drilling.

Mark the locations of all the holes on your workpiece, and then center punch at the marks.  Put the box on the corner of your workbench so that the thin metal is supported directly under where you will punch.  If unsupported, you can easily dent or deform the box with a good hammer blow.  (I wish I had an anvil.)

Drill 1/8” or 5/32” pilot holes to accurately locate the center of all the holes.  (Smaller drill bits tend to more-easily find the center punch dimple, and they wander less than large drill bits.)  Drill the large hole for the XLR connector by using a 7/8” step drill guided into the pilot hole.  Switch bits, and then drill the 3/4” hole for the switch.  Use a de-burring tool to expand the holes until the XLR connector and switch fit.  It takes less than ten minutes of scraping around-and-around the holes — not too much trouble.  Try to make the edges of your hole as square as possible (not sloped), because you don’t have much room for error.  If the hole is sloppy and too big, the XLR connector won’t hide the hole.

It never occurred to me (until now) to look for a 20mm step drill.  That would have made a perfect hole for my switch.  A 24mm step drill would be perfect for the DE5F.  (After all this work was finished, I found metric step drills for twelve bucks on Amazon.  I am hanging my head in shame.)

After the XLR connector fits into the enlarged hole, you can mark the screw holes with a pencil or screech owlscratch awl, or drill them with the connector in place.  I covered the connector with electrical tape to keep chips or aluminum dust from falling into the connector.  Hold the connector square with the bottom of the box, and drill the first hole.  Then insert a screw into this first hole while you drill the second hole.

Mark the outline of the hole for the AC power connector with a scratch awl, and highlight this line with an ultra-fine-point Sharpie.  Drill small holes around the inside of the mark, and then a large hole in the center.  Then nibble or grind away the metal with a burr in your drill press or mototool.  Finish the hole with a small mill file until the connector fits.  Then install the connector to mark the screw holes.

To hold the bottom plate securely, the Bud boxes used to come with self-tapping screws that worked fine, but the current screws don’t have the split point to dig in and cut threads.  Rather than forcing the screws, I simply ran a #6-32 tap into all six of the holes.  Put the tap into a variable-speed reversible battery-powered drill, and run it at very slow speed, and you will be done in two minutes.

It turns out that I don’t really like the look of the illuminated switch that I used (the Mountain 103-R13-135B-02R-EV).  I don’t like the whole rocker lit up, but I guess that would be easily visible from across the stage.  The spec sheet from Mouser says it is an LED, but it looks like a neon bulb.  I would prefer a tiny little red LED, as shown in my drawings.  The switch I used on the power supply in the next section is either obsolete or unfindable, and I can’t find a close replacement without ordering thousands.  Maybe I should have just chosen a plain switch, like Mountain 103-R13-135A2-02-EV or 103-R13-135A-02-EV or E-Switch RR3130ABLKBLKES. There is a power LED on the preamp that will tell you if the power supply is turned on.


Guts of the power supply built around the Mean Well PD-2515 (aerial view):




The power supply from a lower angle:

     
« Last Edit: October 16, 2017, 06:17:25 PM by sean »

Offline sean

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Method 2b.  Build a +15V/-15V power supply with the circuit board from Avion Studios.

Long after I bought the Mean Well power supply, the Molex connectors, and the crimp tool, I discovered that Avion Studios sells a tiny little switching power supply that is only 3” by 1.6”.  The connections in and out are made with soldered wire connections.  This saves you the money for the Molex connectors and that expensive crimp tool.  This tiny power supply circuit board costs only 17 bucks (plus 3 bucks shipping) at Avion Studios website.

This is the power supply card from Avion Studios next to the Mean Well PD-2515:




Avion Studios also sells a pre-built 5-pin power supply for the Rhodes Janus preamp.  Their implementation has a really cute design:  they put the switching power supply in one box on the floor, and the 1/4” outs on a separate little box that hangs up on the left side handle of the piano.  Morgen Sharp at Avion Studios seems like a good guy, and is quick to respond via email.

Since the Avion Studios circuit board is so tiny, I decided to stuff all the components into a smaller box.  I used a Bud CU-234 Econobox.  The diagram below shows the wiring connections and component locations for a 5-pin power supply using the circuit board from Avion Studios:




The drawing shows the PC board as if it were flat on the bottom of the box so that you can clearly see the connections, but I mounted the board on nylon standoffs screwed to the side of the box. 

As mentioned in the section above, you might notice that I have omitted the 680Ω resistors on the audio outputs.  These resistors are shown as R1 and R2 in the schematics for the suitcase bottom – figures 11-3 and 11-4 in chapter 11 of the service manual.  These resistors would provide additional short-circuit protection and maybe some power-on thump protection (if you power up the amp after you plug it into the audio jacks on this power supply).  The preamp itself has 100Ω resistors on both outputs that would protect the op-amp outputs from short circuits, but maybe the power-on spikes are something I should worry about.  If you feel that the 680Ω resistors should be included, they would replace the wires going between the XLR connector and the tip connections of the1/4” jacks. 

The Avion Studios circuit board does not have a common connection point for the DC ground at the outputs.  You have to jumper the two independent outputs together:  my diagram shows the +V1 terminal and the –V2 terminal tied together as the zero voltage reference point.

The Avion Studios board doesn’t have a fuse on the AC power section, so you must add a fuse holder inline inside the box.  Many fuse holders are made for low-voltage automotive or marine applications, and are not appropriate nor rated for AC power.  Get a fuse holder that is difficult to unscrew (so it won’t accidentally open), and is rated for 125 or 250 volts.  The only one that I found that I like and trust is Littelfuse 150274, now ordered as 01500274Z.  That part number is supposed to be for the 1000-piece bulk pack; but it looks like all the resellers buy them in bulk, and list them as singles using the same part number.

The fuse that you use can be anything from 1/2 Amp to 2 Amp slow-blow.  All you need is a fuse current rating large enough to survive the power-on in-rush current, and small enough to prevent a fire or a meltdown of the AC power cord.  I used a 1/2 Amp slow-blow fuse, and it works fine.


This is the shopping list to build a 5-pin power supply with the board from Avion Studios:
1 each  Power Supply board from Avion Studios
1 each  Fuse holder, Littelfuse 01500274Z.
1 each  Fuse, slow-blow, 2AG or 5mm x 20mm, like Littelfuse 218.500 (500mA, SB)
1 each  C14 power inlet connector, like Bulgin PX0580/28
1 each  C13 AC power cord stolen from your old computer
1 each  Bud CU-234 cast aluminum EconoBox, 4.7" x 3.7", 2.2" tall
1 each  Panel-mount 5-pin XLR connector, like Switchcraft DE5F or Seetronic K5F2C
2 each  Switchcraft 11 or L11 mono 1/4" jack
1 each  AC Power Switch, like Mountain 103-R13-135B-02R-EV, 103-R13-135A2-02-EV, 103-R13-135A-02-EV, or E-Switch RR3130ABLKBLKES.
3 each  Quick-disconnect wire terminals for tabs on the switch, either Molex 19003-0017
or TE/AMP 2-520194-2, 3/16” wide, .032” thick (4.75mm x .81mm) – order a few extra
2 each  #4-40, 3/8” or 1/2” flat-head screws and nuts to mount the XLR connector
4 each  #6-32, 3/4” or 1” flat-head screws and nuts to mount the circuit board
4 each  Nylon spacers to mount the circuit board, 1/4” tall, 3/8” diameter
Assorted wire, shrink tubing, solder, and tools from your basement or garage.


You will wind up spending more than $135.00 to assemble all the supplies and tools.

The items specifically in the shopping list will cost seventy-five bucks plus shipping from two suppliers (and a trip to the hardware store).  This assumes that you got the AC power cord for free.  It will cost a little more if you buy an expensive XLR connector.  You should also buy a few bucks worth of heat-shrink tubing for insulating the connections at the AC power inlet, fuse holder, and the switch (unless you use the fully-insulated terminals). 

You will need two cans of spray paint:  a can of primer and a can of topcoat color.  You will have to buy some tools - the step drill and de-burring tool most likely.

Before you know it, you have spent close to one-hundred-and-forty dollars, waited two weeks for shipping, and you haven’t even starting building the thing.  That’s why I recommend that you buy the finished 5-pin power supply from Avion Studios or one of the other folks.


Wiring and Construction:
It is easiest to solder the wires to the XLR connector before it is mounted in the box.  Remember to insert two green wires into pin 1 – one for the ground connection to the circuit board, and one for the audio outputs.  Twist the stripped ends of two green wires together, then cut off the excess, and then solder them to pin 1.  If you make all the wires coming out of the XLR connector 5 or 6 inches long, you can cut them to length later.  It is nice to have extra length in the wires that run across to the circuit board, so that you can easily move it around while bolting it to the box.

All of the AC power connections to the inlet socket should be soldered and insulated with heat-shrink tubing.  The switch connections can be soldered or made using fully-insulated terminal lugs.  Slip the heat-shrink tubing over the wires before you solder the connections, and then shrink the tubing with a heat gun (fancy hair dryer).  You will notice in the diagram that I chose to leave the ground terminal from the AC power cord unconnected.  I decided that I didn’t want the household wiring ground connected to the audio ground and the chassis.

If you decide to build one, please read the other construction sections to get all the tips and tricks that I may not have repeated in this section.


Lessons learned from actually building one:
This is actually the first power supply that I finished, because I was so excited about how small it was going to be (and I had the small Bud box in stock).  I built a test jig for the Avion Studios circuit board by putting the board inside a large plastic pill bottle and mounting a switch on the lid.  I drilled a hole for the wires to come out to the AC power inlet, and made all the AC power connections with quick-disconnect connectors so it could eventually be removed from the bottle.  This way, the power supply was reasonably safe on the workbench, easy to carry around the house, and safe enough to test with the piano.

When it passed all my tests, I un-snapped all the wires to remove the board from the bottle.  When I re-mounted the board in the metal box, I was too stupid and lazy to re-work the quick-disconnect wiring.  That is why it looks like there is an extra mess of wires inside the box.

The guts of the finished power supply:




If your switch doesn’t have the LED indicator (power on) light, then you don’t need the neutral wire connection to the switch.

I used the Seetronic XLR connector on this unit, but I like the look of the Switchcraft DE5F enough that I wish I spent the extra five bucks for it.  Both connectors work perfectly fine.  The Seetronic connector is easier to solder, because it has old-fashioned solder cups (rather than the thin little tabs or fins that are on the Switchcraft DE5F).  The Seetronic solder cups will hold the wire in place while you solder, and will accept two wires easily.  The Switchcraft solder tabs take much less heat to create a joint, but they don’t help hold the wire in place while you try to make the joint.  If the wire moves while the solder is soft, you get an ugly cold solder joint.

When I marked the location for the holes in the little Bud CU-234 box, I put the XLR and the switch a little too close to the corner of the box.  The pillars that provide screw holes for the bottom lid get in the way.  Since I couldn’t get a nut on the back of the screw to mount the XLR connector, I had to use pop rivets.  I also had to shave down the threaded ring that secures the switch.  I was lucky I didn’t have to throw away the box and start over.  So keep your holes away from the corners of the box.  Give yourself extra space, because the step-drill tends to wander.  The final hole might not wind up exactly centered where the pilot hole was.

If you plan to put the circuit board on the side of the box, be careful that you mount it well away from the lip on the bottom lid.  I put the lowest holes 3/8” from the bottom edge of the box.

To mount the circuit board, use four 1/4” tall, 3/8” diameter nylon standoffs (spacers), four 3/4” #6-32 flat-head machine screws, and four #6-32 nuts.  Mount the XLR connector and C14 AC power inlet with #4-40 flat-head machine screws and nuts (they look better than pop rivets). 

One final thing to consider is that just because you can make the box tiny doesn’t mean that tiny is better.  Either size Bud box is certainly small and light enough to fit in your backpack.  The tiny box might fit inside the leg compartment of the piano lid, but I would never dare to risk it getting mangled by the legs and pedal.  I would be just as happy with this power supply if I had built it in the larger CU-247 box.

The finished power supply sitting on keys:


« Last Edit: October 16, 2017, 06:19:16 PM by sean »

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Method 3.  Build an old-fashioned linear-regulated power supply.

When I started all of this, this was my only plan.  Now, it is my least-favorite option.

This is the most risky option.  I am not an expert electronics design engineer, so none of the following (or previous) recipes are fully-vetted and certified safe for human consumption.  I can make no guarantee for safety nor long-term reliability of the power supply described here.  Proceed at your own risk. 

Be careful and prudent about component selection and construction techniques.  Think about safety, think about accidents, and prepare for them in your component selection, construction, and usage of the finished power supply.  For example, during construction, insulate everything that you possibly can with shrinkable tubing.  Mount the transformer to a metal chassis with screws, lockwashers, and a drop of Loctite threadlocker or fingernail polish on the nuts and threads – do everything possible to keep that transformer from breaking loose.  Mount the circuit board securely with large diameter spacers for good support at the corners of the board.  In usage, don’t drop the power supply – if you do, take it apart and inspect it before you use it again.  If the transformer breaks free from the chassis, the power supply can be deadly.  Don’t use a plastic box.  Just don’t.

Component selection and sourcing are important too.  Be very careful to select capacitors with high voltage rating, long life, low ESR, high ripple-current handling, and solid mounting.  I don’t like cutting it close, so I chose electrolytic capacitors rated for 100V.  This required some careful selection to find a 2200uF capacitor that would still fit in the Bud box when mounted vertically.  I chose Nichicon UVR2A222MRD6.  It has good specs for long-life at elevated temperature, high ripple-current handling, and short stubby height (for under four bucks).

Don’t use capacitors found in the junk drawer, or anything that is known to be not-recently manufactured.  If you buy capacitors from DigiKey, Arrow, Mouser or the like, you will get exactly the brand name you requested, and you will get paperwork that certifies that the goods are bona-fide product from the manufacturer.  This paperwork is the boilerplate labelled “Certificate of Conformance” or “Certificate of Compliance” or both.  If you are out west (USA, not Oz), and you have local electronics shops that are not defunct, you might be able to hand-select your parts.  If you pick them from a bin, make sure you can review the part’s exact specs from the manufacturer before you use them.  If you buy from Amazon or eBay or Craigslist, you get no guarantee at all – you frequently get very old stock, sometimes liquidated irregulars or improperly-stored antiques.  Don’t buy that stuff. 

You don't need a big transformer, but most of the nice little PC-board-mounted transformers require a large-quantity minimum purchase.  So I chose a cheap-enough chassis-mount transformer that will still fit in a small box.  I looked for a transformer with a 36V center-tapped output winding.  I got the Bel/Signal 241-5-36, but the Hammond 187C36 would work too.  If you are in Europe or Australia, get a similar transformer that has dual-windings in the primary (like the Bel/Signal DP-241-5-36 or Hammond 186C36), so you can hook it up for 230VAC mains.

Hammond has only a little guidance on selecting a transformer for full-wave-bridge rectification. 
See Hammond Transformer Catalog Chapter 11:  https://www.hammfg.com/files/products/700/hammond-recitifier-guide.pdf
The whole Hammond Transformer Catalog:  https://www.hammfg.com/files/literature/5c.pdf

I didn’t find any helpful design info on the Bel/Signal website (https://www.belfuse.com/signal), but I bought their 241-5-36 transformer anyway.


Here is a shopping list for this linear-regulated antique-design hipster power supply:
1 each  Transformer, 36V Center-Tapped, 12VA, 350mA (Bel/Signal P/N 241-5-36, or Hammond 187C36)
1 each  LM7815  Voltage Regulator, +15V
1 each  LM7915  Voltage Regulator, -15V
1 each  RS407  Bridge Rectifier
2 each  2200uF Aluminum Electrolytic Capacitor, 50V or more, like Nichicon UVR2A222MRD6
2 each  220uF  Aluminum Electrolytic Capacitor, 50V or more
5 each  Quick-disconnect wire terminals for tabs on the transformer, either Molex 19002-0005
or TE/AMP 2-520182-2, 3/16” wide, .020” thick (4.75mm x .51mm) – order a few extra
1 each  C14 power inlet connector, like Bulgin PX0580/28
1 each  C13 AC power cord stolen from your old computer
1 each  Bud CU-247  Cast Aluminum EconoBox
1 each  Panel Mount 5-pin XLR connector, like Switchcraft DE5F or Seetronic K5F2C
2 each  Switchcraft 11 or L11 mono 1/4" jacks
1 each  AC Power Switch, like Mountain 103-R13-135B-02R-EV, 103-R13-135A2-02-EV, 103-R13-135A-02-EV, or E-Switch RR3130ABLKBLKES.
3 each  Quick-disconnect wire terminals for tabs on the switch, either Molex 19003-0017
or TE/AMP 2-520194-2, 3/16” wide, .032” thick (4.75mm x .81mm) – order a few extra
1 each  Fuse Holder, Littelfuse 01500274Z
1 each  Fuse, slow-blow, 2AG or 5mm x 20mm, like Littelfuse 218.500 (500mA, SB)
2 each  Heat sink for TO-220 Voltage Regulators (like 581002B02500G from Aavid)
1 each  Perfboard, like Vector 64P44WE or Keystone 3405, cut down to 2” x 4”
2 each  #6-32, 3/8” or 1/2” flat-head screws and nylon-insert nuts to mount the transformer
4 each  #4-40, 3/8” or 1/2” flat-head screws and nuts to mount the XLR connector and C14
4 each  #6-32, 3/4” or 1” flat-head screws and nuts to mount the circuit board
4 each  Nylon spacers to mount the circuit board, 1/4” tall, 1/2” diameter
Assorted wire, shrink tubing, solder, and tools from your basement or garage.


You will wind up spending more than $150.00 to assemble all the supplies and tools.

The items specifically in the shopping list will cost ninety-five bucks plus shipping from two suppliers (and a trip to the hardware store).  This assumes that you got the AC power cord for free.  It will cost a little more if you buy an expensive XLR connector.  You should also buy a few bucks worth of heat-shrink tubing for insulating the connections at the AC power inlet, fuse holder, and the switch (if you don’t use the fully-insulated terminals). 

You will need two cans of spray paint: one can of primer and one can of topcoat color.  You will have to buy some tools - the step drill and de-burring tool most likely.

Before you know it, you have spent more than one-hundred-and-fifty dollars, waited ages for shipping, and you haven’t even starting building the thing.  That’s why I recommend that you buy the finished 5-pin power supply from Vintage Vibe or one of the other folks.


The diagram below shows the wiring connections for a 5-pin power supply built with a step-down transformer, diode bridge rectifier, capacitors, and integrated-circuit voltage regulators:




When I made this drawing, I had to flip the AC input to the left side, because I couldn’t flip my brain around and draw the circuit from right to left.  I guess I can only think left to right.

As mentioned in the other sections, I have omitted the 680Ω resistors on the audio outputs.  These resistors are shown as R1 and R2 in the schematics for the suitcase bottom – figures 11-3 and 11-4 in chapter 11 of the service manual:  http://www.fenderrhodes.com/org/manual/ch11.html.  These resistors would provide additional short-circuit protection and maybe some power-on thump protection (if you power up the amp after you plug it into the audio jacks on this power supply).  The preamp itself has 100Ω resistors on both outputs that would protect the op-amp outputs from short circuits, but maybe the power-on spikes are something I should worry about.  If you feel that the 680Ω resistors should be included, they would replace the wires going between the XLR connector and the tip connections of the1/4” jacks. 


Wiring and Construction:
The LM7815 and LM7915 are pretty common, and they look identical (TO-220 package).  I can’t read the markings without a magnifying glass, so I mark the metal tab of the LM7815 with a red sharpie, and the LM7915 with a black sharpie.  The two regulators have different pinout connections:

     The LM7815 connections are pin-1=input, pin-2=ground, pin-3=output.
     The LM7915 connections are pin-1=ground, pin-2=input, pin-3=output.

Both regulators have their metal heat-sink tab connected to pin 2.  So on the positive regulator, the metal tab is ground; but on the negative regulator, the metal tab is connected to the input terminal.  This means that you have to be careful to not let their tabs touch each other, and you have to be careful about not letting their heat sinks touch each other (or any other circuit element).  You can decide to be very careful about how you mount the TO-220 device to the heat sink, and electrically insulate the regulator from the heatsink.  You can buy little kits that have a mica pad and washer that will allow you to insert the screw through the hole in the tab without making an electrical connection.  You have to be certain that the threads of the screw do not touch the hole they go through.  I don’t think it is worth the effort.  I bolted the regulators directly to the heat sinks with no mica pad, no silicon grease, no fuss, no muss.  Just keep the heatsinks securely mounted, and keep them separated. 

The 2200uF filter capacitors I chose, Nichicon UVR2A222MRD6, are quite large.  I chose to go with 100V for the working voltage rating, because I want longevity – not leakage.  The higher voltage rating makes the capacitor physically huge, so I carefully chose one that was short and fat, so it would fit in the Bud box when mounted on the circuit board with 1/4” clearance space under the circuit board. 

During pre-construction testing, I hooked up the transformer, the diode bridge rectifier, and a 220Ω ten-Watt load resistor across one half of the output (meaning just the positive 15V side, or just the negative 15V side) – without the voltage regulators or final capacitors.  This created a steady current (something between 68 and 82mA).  I then inserted filter capacitors and measured the ripple voltage with my PicoScope oscilloscope.  The 2200uF capacitor reduced the ripple to just under 400mV peak-to-peak.  Adding a second 2200uF capacitor reduced the ripple to 202mV p-p.  Nice.  I also tried smaller capacitors.  With a 220uF filter capacitor, the ripple voltage was 3.5V p-p; with a 100uF filter capacitor, the ripple was 7.3V p-p. 

Ever curious, I built a complete power supply with 220uF filter caps (instead of 2200uF), with the regulators, and with the final 220uF output caps.  I tested it on my Rhodes preamp.  It was dead quiet.  Sounded great.  The regulators smoothed out all the ripple (which was 3.5V p-p in this test).  The Rhodes Janus preamp only draws half the current of what my test setup simulates, and that lower current greatly decreases the ripple.  I don’t believe that this places any significant strain on the regulators, because we are operating way below their limits.  However, the increased ripple current in the smaller-valued filter capacitors will shorten their lifetime.  So I think it is prudent to stick with the 2200uF filter capacitors.

I tested the transformer by putting two 100Ω ten-Watt resistors from the outputs to the center tap.  The output voltage measured at 39.4V AC RMS, or 19.7V across each resistor.  That means about 197mA current in the 100Ω resistor, almost 3.9Watts.  The resistors got hot very quickly, something like 145ºF.  I didn’t let that go on more than two minutes.  But that assured me that I made a reasonable choice of transformer.  Using the formula from the Hammond catalog: 

VavgDC = .9 x VsecAC(RMS), then my DC output should be .9 x 19.7V = 17.73V.

I think that 17.73V is barely enough to account for the rectifier voltage drop, and the input requirements of the LM7815 and LM7915 regulators.  So it might work.


Lessons learned from actually building one:
This power supply worked fine in all my testing, but I didn’t run it for hundreds of hours, so I can’t guarantee that this design will work perfectly forever.  This is an amateur design with DIY construction techniques, so I can make no guarantees.   

I test-fit all the components on my perf-board, marked where components and screw holes would fit, and estimated that I could fit everything on a board 2” wide by 4” long.  This board would barely fit next to the transformer when mounted in the Bud box.  I could have used a smaller board, but I wanted to leave plenty of air space around the heat sinks.  I cut the perf-board to size using a coping saw, but next time I will try a hacksaw.  After sawing it to size, I filed down the edges until they were smooth and pretty.

I drilled holes for the screws at the corners, and I also drilled holes under the locations of the heat sinks.  In my imagination, I am hoping that this allows more airflow up through the heat sink fins.  I secured the heat sinks to the perfboard with a simple hook made from stiff 18AWG bus wire.  That hook and the soldered leads on the regulators will hold the heat sinks securely.

I decided to put connection headers on each end of the perf-board, and used the same connectors that are on the Mean Well PD-2515.  This makes the board look tidy, and makes the assembly and soldering simpler.  You have to drill out some holes for the studs to go through your perf board, because the header pins are spaced 3.96mm apart.  I am very happy I used the Molex headers and connectors.

I did not put the headers and connectors in the shopping list above, but if you want them, they are:
2 each  Molex 41791-0851 four-position header, available at Arrow for $1.20 each
2 each  Molex 09-50-3041 four-position connector housing
10 each Molex 08-50-0106 female terminal pins (a few extra)
1 each  IWISS SN-28B crimp tool, or similar crimp tool ($23.00 Amazon)


Before drilling the holes to mount the circuit board to the bottom of the box, I carefully tested the location of the transformer and tall capacitors to provide clearance for the sloped sides of the Bud box.  I don’t think I could have fit everything in the box if I hadn’t put all the connectors on one side of the box.  The quick-disconnect terminals stick out from the transformer pretty far, so they interfere with the terminals sticking out from the AC power inlet when you close up the box.  It is a bit of a tight fit, so my component locations were not perfectly chosen.

You can use crimp-on quick-disconnect terminals for the transformer, fuse holder, AC power inlet, and the switch.  This is not much quicker nor easier than soldering.  The fully-insulated crimp terminals eliminate the need to fiddle with shrink tubing on every solder joint.

It was a pain selecting and purchasing the crimp-on quick-disconnect terminals, because the transformer tabs are .020” thick, and the other tabs are .032” thick; and you need to buy red connectors to crimp onto 22AWG wire, and blue connectors to crimp on 16AWG wire.  So I have four different bags of crimp terminals.  I dreamed that it would be nicer than it turned out to be.  See the blurb on crimp terminals at the bottom of the next post.

It would be best to solder the connections on everything except the transformer.  The transformer connections could be soldered if you are quick and careful not to melt the plastic bobbin, and make sure you don’t damage the thin winding wires that are wrapped onto the terminal tabs.  In any case, make sure that you insulate the high-voltage AC power connections to the transformer.


Transformer and circuit board bolted to the bottom lid:


« Last Edit: October 16, 2017, 06:28:07 PM by sean »

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5-Pin Power Supply for Rhodes Janus Preamp - Tools you will need
« Reply #6 on: October 14, 2017, 09:30:29 PM »
Tools you might need:
There are a few metal-working and electronic-assembly tools that you may need to buy. 


7/8” step drill: – no wait!  Get a 20mm and 24mm step drill:
To prepare the metal box, you need to drill two very large holes: one for the XLR connector, and one for the power switch.  You could choose a smaller switch, but you can’t avoid the XLR connector.  The XLR connectors require a hole just a bit larger than 7/8”.  So you should buy a step drill that goes up to 7/8”.  I considered using a hole saw, but I did not test a hole saw on the aluminum Bud boxes.  The step drills work very well if you have a drill press.  I don’t think you should try to use a step drill with a hand drill.  The Bud boxes are pretty thick (.090”), and are stiff and hard.  You can probably push the step drill through the box with a hand drill, but it will be very hard to keep the hole exactly where you want it.  The step drill can drift off center if not controlled precisely, and easily ruin your workpiece.  Before I got the 20mm step drill, I bought a set from Harbor Freight tools:  https://www.harborfreight.com/2-piece-titanium-nitride-coated-high-speed-steel-step-drills-96275.html

I now realize that a 20mm step drill and a 24mm step drill would be ideal.  They are available in sets on Amazon (the set has one that is 20mm and another that goes up to 32mm).


De-Burring Tool:
This tool is used to scrape away a burr and smooth out the edges of any metal or plastic part.  This tool is great for cleaning up any rough hole or sawed edge.  It is also great at removing mold marks or flash from plastic and metal castings.  For this project, it is used to enlarge the holes for the XLR connector and the switch.  Any of the following will work fine: 
http://www.sears.com/unique-s-shop-deburring-tool-kit/p-SPM911512401
http://www.sears.com/unique-s-shop-deburring-tool-set-b-e-series/p-SPM911512651
http://www.sears.com/general-tire-general-swivel-head-deburring-tool-aluminum/p-SPM820381563
http://www.sears.com/cobra-prod-deburring-tool-pst090/p-SPM6449451407
http://www.homedepot.com/p/HDX-Deburring-Tool-HDX090/204218603


Tee-Handle Reamer:
A T-reamer can be used to enlarge holes, or to make holes more perfectly round. 
https://www.harborfreight.com/t-handle-reamer-66936.html


Mototool:
A Dremel mototool is a wonderfully-useful tool.  You don’t need the expensive ones that go to ultra-fast speeds (unless you want to want to engrave diamonds maybe?).  I bet even the cheap single-speed ones are effective.  A mototool would be useful to help carve out the hole for the AC power inlet. 
Get a cylindrical burr bit – Dremel #115:  https://www.dremel.com/en_US/products/-/show-product/accessories/115-high-speed-cutter


A Single-Cut or Double-Cut Burr:
I have a Craftsman 1/2” cylindrical single-cut burr with a 1/4” shank.  It looks like an enormous version of the Dremel #115.  Chuck it into the drill press, and it eats through aluminum.  I used it to grind away at the hole for the AC power connector.  Most of the similar tools online are high-end carbide versions.  Look for a cheap one sold near the die grinders or drill bits at the hardware store, or get a nice kit of burr cutters for fifteen bucks from Amazon.


Center Punch:
To accurately locate drilled holes, you want to start the drill bit in a little dimple to keep the drill bit from wandering.  To make the little dimple, use a center punch.  One light blow from a hammer will make a deep-enough dimple.
http://www.starrett.com/metrology/product-detail/117A


Countersink:
A fluted countersink cutter bit:  82-degree angle with four, five, or six flutes.  (Get a 90-degree angle countersink if you use metric screws.)  Buy the most expensive countersink and largest diameter you can afford.  Cheap ones are usually hateful, but might work well enough if you run them at a very slow speed.  You will use the countersink to smooth rough edges of drilled holes, and also to cut the angled sides of the holes for flat-head screws.

I have one precious good-quality 3/4” diameter countersink.  I keep it protected with a plastic cap.  I like to mount the countersink in a drill bit extension when I am using it by hand.

This cheap kit includes a nice handle:  https://www.harborfreight.com/3-in-1-hex-bit-countersink-tool-68535.html
Plastic cap looks like:  https://www.lowes.com/pd/Waxman-4-Pack-3-4-in-in-Black-Rubber-Tips/3037435
Drill bit extension looks like:  https://www.lowes.com/pd/IRWIN-SPEEDBOR-1-4-in-Hex-Quick-Connect-12-in-Drill-Bit-Extension/1221939


Combination Square:  Use it to measure, plan, align, and mark hole locations.  You already have one, right?
https://upload.wikimedia.org/wikipedia/commons/e/ed/Set_square1.jpg


6” Dial Calipers:   I am an old fart, so I don’t like the new digital ones.  A simple white dial is the easiest and fastest to read, and doesn’t waver or flicker.  I have used expensive Starrett calipers at work, and cheap no-name ones from Harbor Freight Tools at home.  My current set has absolutely no brand name marking on it, but they are solid and easy to read.  They look to be identical to Westward model 4KU74.  Westward 4KU74 is under forty bucks at Grainger.  Notice how the gap on the left side of the sliding portion partially exposes the scale.  That makes the scale really easy to read.   See it at https://www.grainger.com/product/WESTWARD-Dial-Caliper-4KU74

My backup calipers look identical to the HFS product (see B01C6WHQ92 on Amazon for sixteen bucks) – they work perfectly, but are harder to read because the sliding body covers up the scale.  This unfortunate design choice also shows up on most Starrett models.  It seems that most dial calipers are made this way.  The Starrett 3202-6 fixes the problem somewhat.  If the moving jaw comes straight up and covers the scale, I wouldn’t buy it.  Obviously, not many folks agree with me.

I think I bought both of my dial calipers at Harbor Freight Tools, but their current models don’t excite me.  Seems like folks are being herded into buying the digital models.


Mill File and Sand Paper:  I assume that you have a mill file and sand paper.  The new foam sanding blocks or sanding sponges are nice too.  After sanding, you can get smoother finish on an edge or surface by using one of those four-sided fingernail buffing blocks.  You will ruin it, but they are disposable (and free if you find it around the house). 


Soldering Iron:
I don’t think you would have started reading this mess if you didn’t already own a soldering iron, but I could be wrong.  If you don’t have solder and a soldering iron, you can get a perfect one for around $50.00.  But you can live with a cheaper iron.  You don’t need a 60-watt iron.  I have been using my baby-blue 25-watt Weller WP25 iron for more than 35 years.  There is nothing magical about soldering iron design and construction, so even the six-dollar cheapie units work. 

The tip of the soldering iron is pretty important – different shape tips are used for different type work.  I like a flat-blade screwdriver-shaped tip about 1/8” or 3mm wide.  I don’t like round pointy tips, and I don’t want a huge wide tip.  Looks like Apex Tool is selling the WP25 and WP30 with exactly the tip I like – Weller ST3.  The Weller SP25NUS and SP40NUS are both selling for less than $20 on Amazon, but I can’t find replacement tips for these models.

Buy some good-quality solder.  I use 60/40 rosin-core solder of recent vintage, not old stuff.  The old solder had very acidic flux, and was messier to use than the new stuff.  If given the choice, take the mildly-activated rosin flux instead of activated rosin flux.  Kester was my old-timey preferred brand.  Get skinny solder between .032” and .062” diameter (.8mm to 1.5mm).  I think the .050”/1.27mm diameter is perfect, but I used .032” diameter stuff for these power supplies.

You can get rosin-free flux-core solder wire, and water-soluble, and lead-free formulations.  I haven’t tried any of them, and I don’t know how suitable they are for low-wattage soldering at home.  I also feel that the chemicals involved in cleaning off the tiny bit of flux that remains are not worth spending any time near.  The little bit of flux left behind will not significantly corrode your project.  Leave it alone.

Wash your hands every single time after soldering, and don’t eat food while soldering. 

The smoke that is created while soldering will be electrostatically attracted to your face (or the closest person inspecting your work).  The smoke will irritate your eyes.  Set up a fan that is facing away from your soldering area so that the smoke is sucked away.  If the fan is not keeping the smoke out of your eyes, move the fan closer.  I use a tiny fan sitting on the workbench less than 12 inches away.  If you have the fan pointed at you and your soldering iron, it will cool the iron and your workpiece, and you will get uneven results and an overworked soldering iron heating element.


Heat Gun
You can buy a heat gun to shrink the insulation tubing, or you can use your hair dryer on the hottest temperature setting with the slowest fan setting.  Hold your hand over the air intake to further restrict the air flow, and you will get very hot air coming out of the hair dryer.  If you hold your hand over the air intake too long, you may overheat and ruin the hair dryer.  Hold the tubing as close as possible to the heat source, and work quickly to shrink the tubing before the hair dryer fries itself.  Heat the tubing evenly from all sides. 


Needle-nosed pliers and diagonal cutters:
How can you live your life without a pair of needle-nose pliers?   
https://shop.harborfreight.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/i/m/image_18111.jpg
I also like a small pair with a bent tip.  https://upload.wikimedia.org/wikipedia/commons/4/4e/Small_green_bent_nose_pliers_-_D.jpg
You need a sharp little pair of dikes too.  http://www.kleintools.com/catalog/diagonal-cutting-electronics-pliers/electronic-diagonal-cutting-pliers-flush
Minimalists can try to survive with plain-old long-nose pliers with a side cutter.  https://en.wikipedia.org/wiki/File:Long-nosePliers.jpg


Wire strippers:
If you are still using simple wire strippers that look like a notched pair of scissors, you should see what else is out there.  I have an old Speedex model 766-1 stripper (you can find them on eBay).  You can get the similar Klein Tools 11063W at your local hardware store or online for less than $27.00.  They are probably worth every penny.  They will save so much time and frustration.
http://www.kleintools.com/catalog/adjustable-wire-stripperscutters/katapult-wire-strippercutter

I think it is outrageous that the item below still exists, and that the price is $17! 
http://www.homedepot.com/p/Xcelite-Wire-Stripper-with-Spring-and-Adjust-Screw-Stop-101SNV/301049934


Crimp Terminals and Crimping Pliers:
The transformer, switches, AC power inlet, and many other electrical components have tabs that support quick-disconnect terminals.  I like to use fully-insulated quick-disconnect terminals, like TE/AMP FASTON, or Molex Avikrimp.  You don’t have to buy the outrageous $400 crimper (https://www.digikey.com/products/en?mpart=0640010200&v=900).  A cheap pair of crimping pliers works fine.
This one (https://www.harborfreight.com/8-in-four-way-wire-crimperstripper-tool-63307.html) will cost you four bucks:



You can get terminals in pre-packaged assortments, but they never seem to have enough female terminals.  The terminals are a pain to purchase, because what you really want to say is “Just give me an assorted handful for five bucks.”  Sadly, it doesn’t work that way.  So I had to order exactly what I wanted – the quick-disconnect female connector with a full jacket of insulation.

The terminals come in a few different widths and thicknesses, but the common ones that I use are either 3/16” or 1/4” wide, and either .020” or .032” thick.

In the projects shown here:
     the transformer has tabs that are .187” x .020”,
     the switch has tabs that are .187” x .032”,
     and the AC Power Inlet connector has tabs that are .187” x .032”.

You also have to buy the correctly-sized terminal to crimp on the wire diameter you are using.  The industry uses a handy color scheme to tell you what wire is compatible with the insulated crimp terminal:
     Red ones are usually for 18AWG to 22AWG wire.  (Thin wire.)
     Blue ones are usually for 14AWG to 16AWG wire.  (Thick wire.)
     Yellow ones are usually for 10AWG to 12AWG wire.  (Very thick wire.)

So you probably need to buy some red, some blue, some wide, some narrow, some .020” thick, and some .032” thick.

Here is a shopping list for a good assortment of fully-insulated female terminals:
(These are all TE/AMP parts, carried by Arrow, Mouser, Newark, Allied, and Digikey.)
2-520182-2  Red female terminal for .187” x .020” tabs and 18-22AWG wire, fully insulated
2-520194-2  Red female terminal for .187” x .032” tabs and 18-22AWG wire, fully insulated
3-350816-2  Blue female terminal for .187” x .020” tabs and 14-16AWG wire, fully insulated
3-520125-2  Blue female terminal for .187” x .032” tabs and 14-16AWG wire, fully insulated
2-520184-2  Red female terminal for .250” x .020” tabs and 18-22AWG wire, fully insulated
2-520264-2  Red female terminal for .250” x .032” tabs and 18-22AWG wire, fully insulated

If you buy ten of each, that will set you back twenty bucks.  Not cheap.

You could instead choose these Molex fully-insulated female terminals:
19002-0005  Red female terminal for .187” x .020” tabs and 18-22AWG wire, fully insulated
19003-0017  Red female terminal for .187” x .032” tabs and 18-22AWG wire, fully insulated

If you need the male terminals that these mate with, look for an assortment at your local hardware store, or buy them separately:

2-521103-2  Red male terminal with .187" x .020" tab for 18-22AWG wire, full skirt over tab
2-521105-2  Red male terminal with .187" x .032" tab for 18-22AWG wire, full skirt over tab
66023-2  Red male terminal with .250" x .032" tab for 16-22AWG wire, insulated barrel only
66024-6  Blue male terminal with .250" x .032" tab for 14-16AWG wire, insulated barrel only

It makes me want to scream that these cost more than 25 cents each.

Here are some male terminals from Molex:
19022-0006  Male terminal with .187" x .020" tab for 18-22AWG wire, no insulation
19022-0024  Male terminal with .187" x .020" tab for 14-16AWG wire, no insulation
19023-0003  Red male terminal with .187" x .020" tab for 18-22AWG wire, insulated barrel only
19023-0010  Blue male terminal with .187" x .020" tab for 14-16AWG wire, insulated barrel only
19022-0004  Male terminal with .250" x .032" tab for 18-22AWG wire, no insulation
19023-0006  Red male terminal with .250" x .032" tab for 18-22AWG wire, insulated barrel only
19023-0012  Blue male terminal with .250" x .032" tab for 14-16AWG wire, insulated barrel only


There are obviously many many other styles, options, sizes, and brands of suitable quick-disconnect terminals.  If you have the energy, try to make sense out of the product lines from Molex, TE/AMP, 3M, Keystone, and Panduit.


Some of the tools I used:


That is my beloved antique Speedex model 766-1 wire stripper in the upper left corner. 

« Last Edit: October 16, 2017, 07:02:11 PM by sean »

Offline sean

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5-Pin Power Supply for Rhodes Janus Preamp - Polish it or Spray Paint it
« Reply #7 on: October 14, 2017, 09:30:47 PM »
Shiny Silver Polished Finish versus Spray Paint:

Polish it to a Chrome-Like Shine (well, almost):
I still prefer the polished finish over paint, but it is much more work than I expected.  The Bud Econoboxes are not designed to provide a smooth mirror finish.  The cast aluminum is hard and grainy, and very pitted.  The sides of the Bud Econoboxes seem to be sanded at the factory, and the edges of the bottom plate look rough and stone-ground (really course sandpaper used to trim the flash).  The corners where the sides meet are not uniform, they sometimes look like they have become deformed by the factory sanding job.  The top surface and bottom surface are not factory sanded, so you can see the grainy raw casting.  A half hour of filing and sanding makes the box look a lot better.

Smooth the bottom edge of the box without rounding it off (so that it mates with the bottom lid cleanly).  Spend some extra time filing off the corners and smoothing the edges of the lid so that it mates evenly with the top of the box.  You don’t want any overhang or undercut.  I filed off the little feet that are cast around the screw holes. 

I have only one Hammond 1590 box to compare, but the difference is striking.  The corners are very uniformly rounded, and the casting shows much less pitting.  The edges of the bottom plate are not rough, and the corners are nicely rounded to match the top of the box. 

For the polished finish, you must sand down the metal to remove most scratching and as much pitting as possible.  I used an abrasive wheel in my drill press, and the some hand sanding.  If you plan to buff it smooth, you can finish-sand with 220-grit sandpaper.  You don’t really need to go any finer than that.  If you want the sanded grain to remain visible, stop at 120-grit.

No matter how long and hard you buff, a mirror finish is an unattainable goal.  Even if you sanded away all the pitting, the texture of the cast aluminum shows up clearly.  You can see different shades in the metal that look like impurities or inconsistencies in the aluminum.  You can see streaks that appear to be how the hot metal flowed into the mold during the casting.

On the first box I worked on, I purposely created a straight grain on all sides, and then polished it until it was shiny but still showed the grain lines.  The grain looks purposeful (it is ruler straight), and obscures scratches and buffing marks.  It looks good from far away, and looks neat close up.  I think this turned out to be my favorite.

On the second box, I tried to polish away all the scratches, and not show any grain.  I was moderately successful.  It is not a perfect mirror, but it looks great (and it took too much work).

On the final box I worked on, I just created the straight-grained finish, and didn’t polish it at all.  It looks great too.

For buffing, I use a general-purpose blue polishing compound on a six-inch spiral-sewn cotton muslin buffing wheel.  The blue rouge cuts fast enough, and polishes up to a near-mirror finish.  Use medium pressure against the buffing wheel, and let the rouge do the work.  If you are significantly slowing down the buffing wheel, you are pressing too hard.  The buffing machine’s motor may get very hot, so don’t touch or lean on it.  Wear eye protection.

Hold on to the box tightly, and keep your hands away from the area you are buffing – it gets very hot.  If you have a pair of gloves that you are ready to throw away, you can use gloves.  I feel my grip is firmer with bare hands, and I took my time.  The whole buffing operation is very messy.  The rouge gets everywhere.  I set up the buffer out in the grass, so that it doesn’t spew waxy dirty rouge all over the garage.  Be prepared to wash the waxy gunk out of your hair and clothes.

While buffing, it is hard to tell how shiny the surface is because of the layer of blackened rouge that builds up on the box.  I used a second buffing wheel to remove most of the junk, and then washed it off with soap and water.  Buff until you think it is shiny and you are tired of buffing, then take it inside to clean it up.  Once all the polishing compound is cleaned off, you will see that you need another buffing session.  Repeat until you are sick of buffing, and decide that the shine is adequate.  It takes about three two-hour buffing sessions to get the whole box smooth and shiny.  (That’s why I gave up on the last box.)

I scratched up the finish by wiping it on my tee shirt, and another time with a paper towel.  So back to the wheel to buff out those marks.  After that, I only used Kleenex tissues and Q-tips for cleaning.

After buffing and cleaning until you think you can’t get it any shinier, get a stick of white rouge, and polish the box with a loose cotton wheel.  The white rouge does a good job removing any marks from the blue rouge, and making the surface gleam.  I wiped off the remaining white rouge with tissues.

You can also clean off the rouge with a paste or liquid cleaner like Mothers Mag & Aluminum Polish, or Blue Magic.  Brasso now has the word “aluminum” on the label, but I haven’t tried it.  There are other products out there that cost impressive amounts of money.  The Mothers Mag did a fine job of cleaning the rouge off after buffing, so I am glad I had it.  It doesn’t put a polished shine on a plain dull box; it requires that a polished surface existed before (it cleans off oxidation aka tarnish, and gunk).

I wondered how cymbal polish would work on Aluminum.  I do have some Groove Juice; but that stuff is acidic, so it will probably create a white film on the aluminum.  [Hold my beer….]  I couldn’t resist.  I tried a little squirt on the inside of a spare box.  It creates an etched milky mark.  So steer clear of any acidic cleaner, like Bar Keepers Friend, Kaboom, Krud Kutter, or vinegar.

The polishing operation turns out to be pretty expensive:  the buffing machine, buffing wheels, rouge bars, polishing liquid or paste, Kleenex or microfiber towels, and hours of work (plus trips to three hardware stores and the auto-parts store looking for rouge).


Un-Polished Straight Grain (AKA Brushed Aluminum):
As I mentioned, by the time I built the last power supply, I was pretty sick of the buffing wheel.  So I decided to create a straight-grained surface on the box and leave it unpolished.  I used the fine-grit grey-colored wheel in this kit.  I loaded the abrasive wheel into my drill press, and moved the belts to give 1720RPM (1100RPM didn’t cut fast enough, 2340RPM dug in too aggressively.)  Slide the Bud box across the table to make perfectly parallel passes with the tool.  By adjusting the table up and down after each pass, I ran the tool in overlapping passes on all surfaces.  If you concentrate on using even pressure, you can create a very uniform grain on the aluminum box.  It really looks great, and feels pretty nice to handle.  I experimented with fine grain sandpaper as a finishing treatment, but the sandpaper tends to make the grain disappear.  I used a fingernail buffing block to make the box feel super smooth without removing the grain.  I tried using Mothers Mag and Aluminum Polish on the bottom of the box, but it makes the grained finish look dark (filled with tarnish).  Luckily, a bath with Dawn dish soap cleaned off all the black tarnish, and left the finish looking clean and bright.  So don’t use Mothers Mag on a non-polished surface.

The grained surface shows fingerprints just like the shiny polished surfaces do.  I expect both finishes to darken and oxidize with passing time.  I am fine with that, because I have a polished box from a previous project that still looks great after almost a year.

After you have polished the box, you have to be extra careful during final assembly.  It is very easy to scratch the finish with a wrench, screwdriver, or dirt on your work surface.  I laid down a bed of tissues under the box when I had it upside down to install the circuitry. 


Spray Paint:
If you spray paint the box, you should sand it down with 120-grit sandpaper to smooth out the rough casting and remove some of the oxidation.  You can sand again with a finer-grit paper if you feel energetic.  Smooth the bottom edge of the box without rounding it off (so that it mates with the bottom lid cleanly).  Spend some extra time filing off the corners and smoothing the edges of the lid.  Confirm that the corners and edges of the bottom lid line up with the box all the way around.  I filed off the little feet that are cast around the screw holes. 

After filing and sanding, scrub the box with soap and water to remove the dust and grit.  I use plain-old Dawn dish soap, it seems to rinse completely.  After washing the box twice, I rub it down with alcohol to remove any residual oil or residue.  Slap the box against a towel a few times to get the water to squirt out of the screw holes.  Let it dry completely, and make sure there is no water remaining in the screw holes. 

Buy some self-etching primer spray paint from your local auto-parts store.  If they have a matte-finish topcoat in the color of your choice, get that too.  Matte finish looks great.  Before you spray any primer, be maniacal about searching for dust, threads, cotton fibers, hair, or anything else on the surface to be painted.

Apply two or three layers of the self-etching primer (only a few minutes between coats).  I think you can add the top coat after a short drying time of the primer, but I let it dry overnight.  No matter what, follow the directions on the spray cans.  The next day, hit it with two coats of your final color.  Then let it dry and harden for as many days as you can stand. 

When the paint is cured, you should still treat it gently.  Be careful not to scratch it during final assembly.  It is very easy to scratch the finish with a wrench, screwdriver, or dirt on your work surface.  Set the box on a towel or a bed of tissues while you have it upside down to install the circuitry. 
« Last Edit: October 15, 2017, 02:25:26 PM by sean »

Offline sean

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5-Pin Power Supply for Rhodes Janus Preamp - Epilogue
« Reply #8 on: October 14, 2017, 09:31:00 PM »
Epilog
When I started this mess six months ago, I thought I would be done in a weekend.  Then I had the fateful idea to document what I was doing.  Then I found the Mean Well PD-2515, and the project snowballed from there.  So instead of watching TV, this is what I got sucked into.

I really wanted to find a simple wall-wart power adapter that had +15V and -15V outputs.  But I can’t find a unit that can be purchased in low quantities or meet my expectations for price.  If anyone can find old stock of Inventus WM071-1950-D5, that would be interesting.

You could certainly build a power supply fed by two wall-wart power adapters, but it doesn’t save you any money compared to the other options.  For example, you can get two Jameco DCU150050E3021 for a total of $16.00 plus shipping (that's already much more than the Mean Well or Avion Studios supplies).  This wall-wart doesn’t have a voltage regulator inside it (not too much of a problem at low current, but still), and you would have to have two AC plugs or a power strip (awkward).  There are switching wall-warts that would provide good DC voltage regulation, but they aren’t any cheaper.  So I didn’t buy any wall-warts to test.

I would love to try one of the little potted power supplies like the Recom RAC05-15DC/W.  It is only $22.00.  It is truly tiny (2.1" x 1.1" x 0.65" tall), so it could be put in an even smaller chassis.  It could fit inside a cheek block.  I have a bad feeling about this – I may break down and buy one.  (See the similar models from Recom:  RAC05-15DC, RAC06-16DC, RAC06-15DC/W are all the same size.  You could also buy the slightly taller ten-watt model RAC10-15DC/277 and it might run cooler.)

There is an even smaller one from Delta: model AA04D1515A.  Tiny 1.44" x 1.06" x 0.673" tall, four watts, and just under $22!

I haven't tried any of these little potted power supplies, but I am so tempted. 

I gave in to the temptation and bought one.  See the writeup at http://ep-forum.com/smf/index.php?topic=9706.msg53682#msg53682


There are lots of other switching power supplies that would work, but most cost too much money, or are designed for much higher current.  Some of the neat and tiny power supplies require large minimum orders; but there are a few that can be bought one-at-a-time, and some only push the price envelope a little bit. 

The YW515A from Cosel is a cool encapsulated power supply that is less than 2" square and 3/4" tall, but it costs more than $50.00.  It can source up to 170mA from each output.  TDK Lambda KMD15-1515 puts out 500mA, is still pretty small, but also costs more than $50.00

If I were looking to build a power supply for a 4-pin Peterson preamp, I might start with a Mean Well EPS-15-24 (seven bucks!) or EPS-25-24 (twelve and change), or try the Recom RAC15-24SA ($47).  There are 24V wall-warts too:  simple transformers with diode rectifiers, like Jameco DDU240040Z7860 and DDU24005ORS1160, or switching supplies like Triad Magnetics WSU240-0500.  The Peterson schematic shows the DC supply at 25V, but the transistor-based preamp will run fine on 24V.  I almost wish I had an early preamp to test and play with. 

If you find a typo in any of the preceding 15,000 words, please send me a PM so I can fix it.

If you wind up building a power supply using this information, I would love to see photos posted as a reply to this thread.  If these posts convinced you to purchase one of the professionally-made power supplies, I would like to hear about that too.

Sean
« Last Edit: December 03, 2017, 04:43:32 PM by sean »

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5-Pin Power Supply for Rhodes Janus Preamp - Wrapup
« Reply #9 on: October 15, 2017, 03:55:33 AM »

This worked out pretty well, and looks mostly how it it should.  I will continue to try to resolve the links in the next few days, but for now, I am locked out of the posts that have lots of links (due to automated security limits).

The circuit diagrams should not have that light blue/gray background - it should be white.  It might take me a while to fix that.  I will try to re-save those images with an explicitly white background, and see if that works.  You would expect that blank paper would be rendered as white, but oh well.  Blasted web design tools.

If the images look too large, you can right click on them and select "view image" and that will usually zoom the image to the current window size or something more manageable than full size.

If anybody wants any of the drawing in their original Libre Office Draw format (.odg) or as a pdf for printing, just send me a PM.


Sean
« Last Edit: October 15, 2017, 02:31:13 PM by sean »

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Re: 5-Pin Power Supply for Rhodes Janus Preamp - DIY
« Reply #10 on: October 16, 2017, 01:56:12 PM »
This is totally magnificent.  The lunchbox is brilliant :)
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Offline sean

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Re: 5-Pin Power Supply for Rhodes Janus Preamp - Lunchbox
« Reply #11 on: October 16, 2017, 04:25:48 PM »
The lunchbox would look even cooler if I had used this one:

http://www.musiciansfriend.com/lifestyle/fender-fender-black-tolex-lunch-box/k45630000000000
The tolex makes this one look great!   Sad that the rivets that hold the lunchbox together make it look like the trim on a Roland Jazz Chorus.

The lunchbox I used was found in the basement, and my oldest daughter was mildy upset that I used it (not that she had touched it in ten years).
Believe it or not, the baby socks really do work.  I can shake the box, and the batteries don't flop around.

I had way too much fun with this project.  I am kinda sad that it is finished, but I have at least two Rhodes/Electronics projects planned for this winter.  I hope I can get them done faster than this mess.

Sean


« Last Edit: October 19, 2017, 02:07:34 PM by sean »

Offline squarebubble

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Re: 5-Pin Power Supply for Rhodes Janus Preamp - DIY
« Reply #12 on: October 17, 2017, 04:40:32 AM »
Amazing stuff!! Do you have any plans to design a power-on thump protection? I had a power supply designed by a friend and I have that exact problem. If the unit is powered up whilst connected to a live amp, I get a big thump and similarly if it is powered down whilst connected to a live amp, there is a loud audible thump too. Unfortunately my friend isn't in the position to help me anymore, but he did suggest adding a 12-15V AC relay into the circuit.

Offline JanustheManus

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Re: 5-Pin Power Supply for Rhodes Janus Preamp - DIY
« Reply #13 on: October 17, 2017, 10:09:46 AM »
Amazing write up Sean!
« Last Edit: October 17, 2017, 10:13:47 AM by JanustheManus »
Why didn't Fender Rhodes stick with the lovely reflective Sparkle Top rail?

Offline sean

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Re: 5-Pin Power Supply for Rhodes Janus Preamp - thump
« Reply #14 on: October 19, 2017, 02:32:39 PM »

SquareBubble -

I have no plans to play with automated thump protection.   Usually, thump protection is built into the power amplifier to protect the speakers.  I have had home stereo systems that had relay-based protection circuits (with a notable mechanical ta-click sound a second after powering on).  I think modern amplifiers might implement this with MOSFETs or JFETs.  Lots of the car audio integrated circuits have power-on delays.

If you really wanted to implement thump protection between the preamp and the power amp, you could simply add the relay circuit to the audio outputs of this power supply.  The circuit at http://www.electronicecircuits.com/electronic-circuits/power-amplifier-speaker-protection-circuit-schematic is what I would try first.  You're gonna need a bigger boat - I mean, box.

Rather than fuss with the relay and the constant drain of 30mA to keep the relay closed, I think it is easy enough to manually turn all the volume knobs to zero, plug in the audio cables after the power supplies stabilize, and heed the advice of Cleavon Little:  "Hold your ears, folks...!"

Sean





It's showtime!
« Last Edit: October 19, 2017, 02:34:53 PM by sean »

Offline squarebubble

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Re: 5-Pin Power Supply for Rhodes Janus Preamp - DIY
« Reply #15 on: October 24, 2017, 08:08:42 AM »
Thanks Sean for supplying that link. Being non-technically minded, I fear I would make a pigs ear of it and blow something up!!

Making sure the volume is turned down to zero, is definitely the simplest option for now.

Thanks again :)