Messages

The knobs with the Fender "F" were used through 1978 on stage pianos.  They switched to the Janus style black knobs in 1979.

There was a short period in about 1974 they were using all silver metal knobs on stage pianos with a black indicator line.

Tim
retrolinear.com

Goldphinga,

We here at RL do not feel it is necessary to use wax, as we have never had to use wax on pianos ranging from the beginning to the end of Rhodes production that use rubber grommets.  But, it is a certainly a valid method to lubricate threads for driving screws into hard woods.  One can also use plain bar soap, such as Ivory, in a pinch. 

Tim
retrolinear.com

Hi David,

Sorry to hear you are having difficulty.  Here is how we install our kits to insure proper seating and performance:

1. Remove the old screw, grommet, and washer while holding the tonebar in position so that it does not angle up or down. 
2. Insert a #2 Phillips head screwdriver in the hole in the tonebar to insure the spring under the tonebar is centered.
3.  Insert the new grommet, seating it completely.  Make sure the spring under the tonebar fits around the grommet properly.
4.  Install the screw and washer.

If you do it any other way (i.e. drive the whole screw, washer and grommet in together at once), you risk the spring or screw deforming the grommet enough that proper seating may not take place.  Our grommets are the harder of the two currently available, so they will not seat as easily if the screw is put in them first.

As for he cosmetics, we chose our plating to keep cost down.  We use all US suppliers for our grommets and hardware, so the cost is already higher.  Most of the time the cover is on the piano, so it is not seen unless the piano is being worked on.

If you have any other problems, I'd like to know about it.  I have never had any complaints about seating from any customer using our product... quite the contrary, actually.

Regards,
Tim
retrolinear.com

It is a high pass filter network for the last group of keys (a little more than an octave). It is used to filter out the thunk/clunk sound of the hammer hitting the upper tines.  The low frequency thunk is more pronounced in that upper octave, so it was needed to filter it out.  Having the extra pickups and the filter network in an 88 changes the overall pickup network slightly enough that it makes an 88 sound a little different than 73 note pianos- 88s are often not quite as bright in the mids and upper mids.

Tim
Retrolinear.com

Just for the record- we (Retrolinear) do not use socket head cap screws on Rhodes pianos. 
I spoke with Ken Rich and he does not either.

In a situation like this we would put the assembly in a vise, drill the head off the old screw, remove the remaining threaded part of the screw from the tone generator assembly and replace it with a spare.

Your Twin Reverb expects an instrument level input, i.e. a passive electric guitar, or a Rhodes harp.  These have very low output levels and need a high impedance input.   The output of your Peterson is line level.  The Twin reverb has too much gain in the front end for a line level input.  You either need to pad the output of the Peterson to use it with the Twin or select a different amp with line level inputs.  The Peterson already colors the sound of the piano, so I am not sure putting it into a Twin (even at the right level) will sound all that great.

Good luck!

Tim
retrolinear.com

Yes, that is correct... The preamp on the reed bars is eliminated.

If you need any further assistance with the installation, please contact us directly at

info@retrolinear.com

Thanks,
Tim
Retrolinear.com

Hi,

If you have an 80W Peterson Cabinet (FR7054), it expects two 32 ohm drivers in parallel on each channel for an effective 16 ohms.  You can also wire two 8 ohm speakers in series to also get 16 ohms and it will be OK.

If you have a 100W Janus/Haigler cabinet (FR7710), then you will need to use two 8 ohm drivers in parallel on each channel.  The Janus/Haigler amplifiers expect to see a 4 ohm load to deliver their full power.

The type of magnet you select does not matter as far as the electronics go, as Real MC said, it is a matter of preference sound wise.

The aluminum extrusions are identical and can be used on either side. 

The shims on top of the aluminum extrusions may or may not be identical...

All bets are off for earlier pianos with wood supports, but shims are used on these as well, so there were probably many variants over the years.

Just make sure after you do the swap you get the correct escapement across the keyboard and shim accordingly if necessary.
Also be very careful resetting strikeline once the swap is completed.

Tim

Absolutely.  Just make sure to choose a resistor with adequate wattage and then leave space for it to cool.

Disspating 100mA at 18V in a 180 ohm dummy load is almost 2W-  the resistor will get pretty warm!

Unfortunately your power supply will not qualify for energyStar status.

Tim

Voltergeist,

The following is based on looking at the schematic only.  There may  have been revisions to the actual electronics that do not match the published schematics.  I do not have a Jordan preamp available to test.

I ran a quick 'worst case' type calculation.  If you assume the Zener clamps the supply for the preamp electronics at 13.5V, and all the preamp transistor's collector-emitters are shorted out, pulling from the supply will be two 12k resistors (about 2.25mA total), one 6.8k resistor (about 2mA) and the vibrato oscillator and bias (about 500uA, on the very high side).  Add that up and you get 4.75mA.  Even though the calcs are already rounded up, we'll add ~20% slop on top of that. Call it 5.7mA .

There are no published voltages on the schematic, but the power supply caps are 35V, so assume the power supply is +/-35V.  There is a 1.5k 1W resistor feeding the 1/4" socket that feeds the preamp off the 35V supply.  So, if the zener is clamping the preamp supply to 13.5V, you will have (35V-13.5V)/(1.5k + 390) = 11.3mA.  So the zener eats whatever is left after our very high estimate of 5.7mA is eaten by the preamp electronics. 

If you are powering the preamp directly from an external supply, without an amplifier/power supply base, I would choose a DC supply that is 18V and could supply at least 25mA.  This would pretty closely simulate the Jordan power supply.   Careful- if you choose an unregulated wall wart that has too much current capacity, its output will be higher than 18V since the preamp will only draw about 11.3mA.


Tim

From what we can tell, the felt tips are made from standard piano hammer felt cut into cubes.
All the felt appears to be the same stock, and the different hardnesses are treated with different amounts of hammer hardening lacquer or two different types of hardening lacquer.

From what we have seen (which is limited since these pianos are rare) there are 3 different hardnesses of felt cubes (lows (no hardener), mids (light hardener), upper mids (heavy hardener), and finally the felt coated wood tips for the high treble.  It will take some practice to get consistent results.

Piano hammer felt scrap trimmings suitable for cutting into cubes and hardeners are available from piano supply vendors.  We can also get these materials for you.  Contact us if interested.

Tim
retrolinear.com

That cable config will work, but you are effectively shorting the L and R channels of the iPod together.  It can probably handle that (there is likely some level of protection), but I would only connect either the left (white) or right (red) to the Y connector and leave the other disconnected.  This is for the iPods sake, not the preamp.  The preamp has a signal input which it is OK with, as long as it isn't too hot.  Keep the volume on your iPod low.  You don't want to clip the gain stage in the preamp.

And, to agree with voltergeist, we always have problems with the old headphone jacks on the Peterson power supplies.  We always replace them and the 330 ohm resistors too.  We have also had bad 3A speaker fuses on the power supply regulator board cause imbalances.

Tim

Martin,

The preamp does expect a mono source.  Since it sounds like you have the power supply/amps sorted out we can assume that is OK.  If you have an imbalance coming from the preamp, it could be due to:

a) bad or incorrect bulb in one channel
b) bad opto in one channel
c) opto sensor/bulb proximity issue
d) metal can missing from one of the opto/bulb pairs
e) bad circuitry that drives the bulbs, leading to different brightnesses
f) bad circuitry in one of the channels once the signal is 'split' to stereo, pre or post opto
g) bad connector or cable from preamp to power supply module
h) some type of loading on one channel between the preamp and power amp.  You will need an ohmmeter to make sure both impedances are about equal.

Power up the preamp with the lid off, make sure both bulbs are the same brightness.  Then you can narrow it down from there.  You can use a simple AC voltmeter instead of a scope to feed a signal into the preamp and  find where in the chain the signal becomes weak.  Just use a sine wave test tone at about 200Hz from your ipod.  You should be able to make up a test file for you ipod on a PC or find a test tone on the web somewhere.

Good luck,
Tim

A few different manufacturers made the original drivers... among them were Jensen, Utah, and CTS.

All Peterson cabinet speakers were 32 ohm alnicos except for the last Peterson units in 1977, where they were ceramic 32 ohm drivers.

Jensen currently makes a replica of the original alnicos called the P12Q - 32 ohm.  They are available from numerous sources, us included.  They are expensive, but are the closest to the originals in terms of frequency response.  We use them in our restorations, or have the originals reconed if the condition of the basket and magnet are acceptable.

We have found that many of the original speakers need to be replaced or reconed due to warpage of the spider/cone, dried out cones, or loose magnets.  These problems usually exhibit themselves as rattles, buzzes, or other strange audio artifacts at certain frequencies and volumes due to voice coil rub.

You can also use two 8 ohm 12" drivers of your choice on each channel and wire them in series rather than parallel.  The amp still sees 16 ohms, so it will be happy.

Tim
retrolinear.com

Actually I am pretty sure Wurlitzer only made keybeds for Rhodes for about a year or so in 1976.

Pratt-Read resumed production thereafter.  You can tell by the style of the number stampings in the keys, the keytops, and cuts in the keysticks themselves.  Wurlitzer keys had square cuts with hard 90 deg. corners, Pratt-Read had rounded corners.

This is also why the 1976 keytops have a tendency to hairline crack-- so do Wurly 200 keys!

The easiest thing to spot about the Wurlitzer keys is that there is a black plastic tab on the back of the sharps.  Pratt Read sharps from about 1974 onward don't have the tab.  The key is instead painted black on top behind the plastic keytop.

Despite the different keycaps- Early 70s round tops, mid 70's flat that 'yellow' on front, and late 70s, those keybeds are all by Pratt-Read.

Tim

Hello all,

I have already reverse engineered the 'floater board' Eddie Reynolds EQ as shown on the fenderrhodesla.com site once before.  I can't locate the schematic right now, but I do have it somewhere around here.  The floating board unit I analyzed required a split power supply (+/- 15V) not unlike the Janus preamp, in addition to the stock 24V for the tremolo circuit, so adding one to a Peterson base requires fairly extensive modification of the power supply unit.

The "E" piano appears to be a different circuit.  I'd be happy to carefully reverse engineer that as well if the owner was willing to send the preamp to us, but given that there is only one known one in existence, shipping it may not be the best idea.  Hi res photos could work, but may not allow us to uncover all the secrets.  I would also want to put it up on the Audio Precision to map out its characteristics, and then also verify everything with SPICE simulations.

In any case, while I am sure the "E" piano still works and has a unique sound, I highly doubt it is anywhere near where it was when the legendary recordings were made.  It probably needs to be brought back by a tech who knows what they are doing and can figure out how to properly understand the mods (both mechanical and electronic) that were done to it and then adjust the piano to work optimally within the characteristics of those mods.


Tim
retrolinear.com

Steveo-

Yes, indeed, Lucy is not tuned.  Neither are Grace or Wilma, for that matter... 

Donald has the Rhodes stretch tuned to match the Steinway grand so we were specifically asked not to tune the pianos for pitch since it would just make more work for everybody involved.

We generally tune our pianos equal temperament, but that isn't usable in this situation.

Probably should have made that clear in the earlier post. 

Also, FYI:

Lucy  1973
Grace mid- 1976
Wilma late-1976

Hello,

The solder on the end of your reed is starting to separate from the reed.  It hasn't completely let go yet, but if you take the reed out, put it under a good light and gently pry at the solder weight with your fingernail you will see it is starting to separate from the reed.  This usually happens at the back end (closer to the mounting hole).  I would suggest removing the old solder and building up a new pyramid.  If you leave it as-is the solder pyramid will eventually fly off... so I would just take care of it while you are in there.

Good luck!

Tim
retrolinear.com

I actually think you are experiencing the magic of the suitcase speaker cabinet.

Many folks think that the stereo pan from the Rhodes preamp circuit is the whole Rhodes stereo effect, but that is really only 50% of the story.

That is not to say I haven't seen preamps or power amps with significant differences on the outputs, but if all appears to be working and measuring right, especially after you swap amp modules, inputs, outputs, check with external amps from the line outs, etc...

The Rhodes suitcase speaker cabinet is ported on only one side (the left as you sit at the piano).  The speakers on the left side are very close to these ports where as the speakers on the right side are far from them.  The left speakers virtually or almost run in an 'open back' configuration because of the port openings- the speaker cabinet's resonance has little effect on the sound from the left speakers.  The right speakers, however, are far from the ports and there is a significant resonant chamber created between these speakers and the ports.  As a result, you get more bass response from the right set of speakers.  Now, as the sound pans from right to left, you not only get the direct pan effect, but also a shift in tone and EQ.  There are also some effects from the room, reflections, and the like as the sound moves-- but the cabinet porting is more dominant.  Rhodes Suitcase magic!

Some of you already know I am working on my own Rhodes preamp (called the PeterPan) that EXACTLY captures the Peterson panning envelope.  In addition there will be a cabinet simulator added to the circuit to mimic the suitcase cabinet effect (which can be disabled if you don't want it).  Using a hybrid of analog and digital techniques, this can be accomplished.  No optos, LEDs, or light bulbs to burn out, drift, or match.  Audio path remains entirely analog.  The proto works, I hope to have the product design finished relatively soon.  I spend more time trying to work out the physical interface and control layout than the circuit itself!

I used to work in industry designing high performance analog and mixed signal ICs for medical and automotive apps.  I will always be envious of Doug Curtis (RIP) of CEM fame who was lucky enough to be in the right place at the right time and have the opportunity to design ICs for synths.  Even he had to move into designing for commerical and industrial markets when the analog polysynths started dying off in the 80s.  I left industry to start Retrolinear, thinking I'd have time to design lots of cool electronic products.  Well, starting the business and being inundated with service work has still taken significant time away from the design process!  But it is coming....

In any case, here is a video of the 1st proto in action.  Please excuse the poor audio quality (due to camera and editing) and mismatched amps, etc.

http://www.youtube.com/watch?v=uy2opjzG8T4

Comments/suggestions are welcome!

Best,
Tim
retrolinear.com

All,

It seems that the non-technical aspects of this topic have now been fully explored... and I think we can give it a rest.

As the designer of the Warneck Research products, I would like to have a chance to discuss some of the technical aspects of our design methodology.

One thing I have noticed is that there seems to be an inherent bias in the music world against ICs.  As a designer of circuits using ICs and an IC designer myself, I personally feel this prejudice is not justifiable. 

Tons of beloved classic effects pedals (Mutron, MXR, EH) and analog synths (Sequential Circuits, Oberheim, etc.)  are completely loaded with ICs, and I doubt anyone here would say that they sound sterile.  People spend a lot of money on BBD IC based analog delays... because they sound so 'warm' and 'organic.'  High end companies like Neve put ICs in many of their designs that people go crazy over.  Many of the finest, well-respected mixing consoles have IC based VCAs and other circuits in them.  Now, a company named Strymon is making DSP chip based digital effects pedals that are simply breathtaking- and taking the guitar world by storm.  And we all know guitarists are generally far more critical than keyboard players in searching for that elusive thing called tone.

Early on, when ICs were first being introduced, they indeed had shortcomings.  Companies were anxious to be on the cutting edge, and used them in their designs perhaps a bit prematurely... sacrificing sound quality and reliability.  Early analog ICs, while groundbreaking at the time, were sluggish, noisy, and terrible for audio.  Many big audio companies, even today, still manufacture most consumer and 'prosumer' equipment with the same low-performance ICs that were being used in the 70s and early 80s.  This helps continue the perception among many that ICs can't and don't sound good.

If one opens a DigiKey or Mouser catalog, there are a staggering number of opamps and other analog ICs available.  In order to design a high performance audio circuit, one must know what to look for among these thousands of parts.  Each of them has different specs for different purposes in a circuit design, and the right parts need to be selected for the right job.  Calculations need to be run, measurements need to be taken.  Questions need to be answered regarding noise levels, offsets, slew rates, THD, bandwidth, input stage technology (FET or BJT) and several other specs.  Once this space is defined, one can select the appropriate part and match it to the application, yielding the desired result.  The math and physics never lie.

All of our products are designed in this way- each critical component is selected for the application after calculations and measurements, and the circuit then built around it.  Circuit simulations are run using SPICE to check that noise, frequency response, and transient response of the circuit is as desired.  Calculations are also run to make sure that all components are operating within their safe operating area (SOA) to ensure years of trouble-free performance.  Our designs are not copies of the original Wurlitzer circuits with a few enhancements nor copies of other circuits from elsewhere rearranged or reorganized in a new way... but original and well-engineered from the ground up.

As for the Wurlitzer EPs, the original 200 amp design was a disaster.  The circuit architecture was not optimized for the application and it was very inefficient.  If it was so great, why would Wurlitzer continue to revise it and then eventually abandon it in favor of the 200A design?  The 200A design was much better from a circuit design and architecture standpoint but still had its own share of problems (noise and reliability) due to the separate preamp board and all of the messy wiring and connectors that ran between everything in the piano.  It had other shortcomings too... in fact, both original 200 and 200A designs have elements in them that are dependent on poorly controlled transistor characteristics that drift with time and temperature, hence the need to hand select resistors and transistors for each board on the production line.  These devices continue to drift as they age, resulting in problems like cross-over distortion or runaway output stages that blow fuses.  Even if one was to fully rebuild (or reconstruct) an original 200 or 200A board with all new higher performance components, the same problems and deficiencies would continue to pop up for years to come because of the inherent architecture of those circuits.

There are plenty of examples of terrible tube, transistor, and IC based circuits.  Likewise, there are all excellent examples of each.  The same goes for an instrument like an acoustic guitar.  They are all pretty much built out of wood and strings, but the kind of wood and the attention to design and craftsmanship can yield drastically different results. 

I am certain that if our products were not high-end performers they would not have the endorsement of Ken Rich or any of the artists that use them.  Being a vintage enthusiast, Ken himself was highly skeptical of the IC based design when I first made contact with him to get feedback on the beta unit.  Once he heard it and had me tweak the EQ a little bit, he fell in love with the 200 all over again.

Best regards,
Tim Warneck
Retrolinear Inc. 

Glad I could help clear things up.

Generally speaking, ceramic caps are not unreliable.  They typically last a long time when operated within their ratings but they can sometimes crack due to mechanical stress, and even become microphonic.  Ceramic caps, depending on the type, can also have large temperature coeffcients (their value changes with temperature).  I would not expect them to fail due to electrical stress in a circuit like the 200A amplifier, but failures are always possible.

Ceramic caps across the AC line, however- that is a different story.  The power coming out of your outlets (in the US) is almost never a crisp clean 60Hz sine wave.  There are transient spikes, noise, surges, and a multitude of other things riding on the wave.  Line noise has gotten worse with the mainstreaming of switching power supplies and non-incandescent lighting.  These transients are what slowly degrade these ceramic and old film line caps.  They were not made with self healing properties, and eventually they can short out.  Caps across the AC line must survive some of the toughest conditions, and the old ones will eventually break down.  This is why there are new standards for these "X" and "Y" type safety caps... they build them as bullet-proof as possible.  Of course, as a result of this, they are large and expensive compared to a standard ceramic or film cap of the same value and voltage rating.

Tim
www.retrolinear.com

All,

I am certainly not trying to be argumentative, but for safety reasons the capacitor should be removed (cut out) completely from the circuit.  No product designed today could be brought to market with a cap between AC line and an ungrounded (un-earthed) chassis.

Only the line-to-ground capacitor should be removed.  My Wurly 120 schematic shows a single such cap, but in some other old electronic equipment, you may find 2 'line-to-ground' caps (one from each side of the line to the chassis (ground)).  In this case, BOTH should be removed.

The original ceramic or film capacitors used between the AC line and chassis on older equipment are not rated for this kind of application.  If they should short, they can allow potentially lethal voltages to appear on the equipment chassis.

In modern day electronics, a cap that needs to go from line to earth ground must be "Y" safety rated.  This kind of cap cannot short out and will self heal in the case of an overvoltage transient.  However, even a safety rated capacitor can only be used when the appliance is earth grounded via the '3rd prong' .

You can read about this here:
http://www.kemet.com/kemet/web/homepage/kechome.nsf/file/KEMET%20Kollege%20Presentations/$file/EvoxRifaRFIandSMD.pdf

The first couple of slides have the useful information... the rest is marketing gibberish for engineers/designers.

If you wanted to go a step further towards improving the safety of your unit, you could replace the old 2-prong socket on the amp with an IEC connector (which I think is a good idea).  For the IEC connector to be effective, its earth ground pin must be connected to the chassis.  And, if you go through the trouble of installing a 3 prong plug, never defeat it by using a ground cheater adapter on the AC plug!

Again, the cap may not be the only or main problem.  Other possibilities are a short in the power transformer, AC wiring touching the chassis directly in the amp itself, a short within the wiring to the power switch (cracked insulation), a short in the power switch endblock, etc.

Just to check to be sure, after cutting out the old cap and with the piano unplugged from the AC mains, take a multimeter and make sure there is no continuity between either side of the AC line and chassis.  If the meter reads open for each 'prong' of the AC plug with respect to the chassis (test leads between the chassis and each prong of the 2-prong socket, one at a time), you are OK.  Do this test with the piano unplugged from the wall, and the power switch in both the on and off positions.  Make sure you have the multi-pin connector that goes to the power switch and volume controls plugged into the proper socket on the amp chassis while running these tests.

To sum it up:
1.  Cut out the old line-to-ground cap.  No exceptions for safety reasons.
2.  Check the continuity of each AC line terminal/prong to chassis with the power switch on and off (with piano unplugged from AC power).  It should always read open.  If it doesn't you will need to track down and eliminate the short.
3.  Leave out the cap if you leave it 2-prong.
4.  If you add an IEC connector and ground the chassis to earth ground, you can either:
    a) leave out the cap (recommended)
    b) replace it with a new "Y" rated safety cap of the same value.. but never defeat the earth ground.

Finally, as always, if any of this is unfamiliar or uncomfortable territory, and you don't understand 100% what you are doing, *don't do it.*

Tim
www.retrolinear.com

Hi,

If you take a look at the schematic for the 120 (available out there on the web) you will notice that there is a .1uF cap between one leg of the AC mains and ground.  In the 120, the amp chassis is this ground.

This cap is probably shorted or going bad and needs to be removed for safety reasons.  To be frank, even if it isn't going bad, it should still be removed.  You can do it yourself if you can properly read the schematic, trace it, and identify it under the chassis.  You are working with very high voltage tube stuff here so if you do not know how to work on tube equipment safely (discharging HV caps, etc.), *don't do it.*  I would recommend having it professionally serviced if this is unfamiliar territory.

If the piano was used as someone's science fair project,  there could also be an unintended short somewhere else in the chassis causing this problem.

Here is why (if you are interested):

In the early days, it was common to put these caps on tube and other electronic equipment as it was there to help shunt RF interference.  Nowadays, this is considered unsafe (for the reasons you discovered), unless it is a certain type and value of cap rated for this safety application and the chassis is earth grounded (which it isn't with only a 2 prong plug).  In your 120, this cap is probably shorted or working improperly and inducing line voltage onto the chassis.  This is why you are getting zapped... especially when AC 'hot' is connected to that side of the transformer and cap. 

When you flip the plug, you are reversing hot and neutral (which 4kinga noted).  Since neutral is 'close' to earth ground you won't feel the shock (it is connected to earth ground in your breaker/fuse panel but floats a little above ground because it is the return path for AC line current to the panel).  Imposing line (or neutral) into your sensitive audio circuits through a shorted cap will induce the hum when the other equipment is properly grounded and expecting signals referenced to earth ground (as most modern day equipment does). 

It should also be noted here that '3rd prong' ground is earth ground and is NOT supposed to carry current in normal circumstances-- this way ensuring that it IS at earth ground potential at your wall outlets and the chassis of whatever devices are using the 3rd prong.

Again, a lot of older electronic gear has these caps between the line and the chassis (ground) that cause all sorts of shocking problems.  In your case, if removing the cap does not fix the problem, then I would look at ground loop issues.

All the best,
Tim
Retrolinear Inc (formerly Keyboard Cottage)
www.retrolinear.com

The picture of the Wurly 106 with three knobs that Michael posted was done by Ken Rich at Ken Rich Sound Services in Los Angeles.  As far as I know it now belongs to Page McConnell in Phish.

I designed and produce both the new 200 series amp board and the variable speed vibrato upgrade (the 3rd knob) that Ken now puts in almost all his Wurlitzers.

You can read about the Warneck Research EP200 amp replacement in the 'New Gear' section of this month's Keyboard Magazine.

Tim
Keyboard Cottage/Warneck Research

Milos,

All of the Janus preamp schematics on the website are 'factory' schematics.  I did not design or modify any of them.  I simply scanned all three and sent them to James to post on the website.  Rhodes revised the design of the Janus preamp twice since it was introduced in 1977.  Each preamp is slightly different in sound (especially the vibrato effect) as you discovered. The majority of the Janus preamps out there match the 2nd schematic in the series, and are found on late Mk1 and earlier Mk2 pianos.

Tim

[Wurlitzer 200 Amplifier Boards]

Keyboard Cottage/Warneck Research is proud to announce some of our new products.

Wurlitzer 200 Amplifier Boards

Features:

- faithfully reproduces the EQ curve and sound shaping characteristics of a properly restored original 200 series amplifier
-  authentic vibrato
-  very low noise
-  improved power amplifier
-  selectable variable or fixed line-out configuration
-  high reliability
-  high quality components
-  drop-in replacement
-  solder-free installation
-  comes complete with reed bar shield kit
-  volume production October 2009

Description:

The Wurlitzer 200 replacement amplifier is designed to faithfully reproduce the sound and characteristics of the original Model 200 amplifier -- only without all the noise.  Although one can rebuild an existing amplifier with new, high performance components, the inherent architecture of the stock amp will still create an undesirable amount of noise.  Completely redesigned from the ground up, the new amp employs low noise circuit and layout techniques.  When coupled with reed bar shields (included) to minimize 60Hz hum, the performance is unmatched -- it even outperforms fully restored 200A amplifiers.   Terminal blocks allow easy installation without the need to solder.

As for the sound, we were fortunate to work with Ken Rich at Ken Rich Sound Services in LA to further optimize the EQ curve.  Ken has been working on keyboards since the 70s and is one of the music industry's best kept secrets.  He has done full restorations and provides service for many of the major touring artists including Steely Dan, Lenny Kravitz, and George Duke.  We are happy to have the help of his golden ears, experience, and no compromises, no excuses approach to vintage keyboards.   He wholeheartedly endorses the new amp and is already using it in several professional touring rigs.

Beta units have been in the field with touring musicians and recording studios for almost 2 years without any issues.


Variable Speed Vibrato Upgrade for Wurlitzer 200/200A

Features:

- original style sine waveform
- linear variable speed control (approximately 1Hz to 15Hz)
- simple 3 wire hookup
- mounting bracket included
- new faceplate included
- works with our new 200 amp and stock 200A amps
- developed with Ken Rich
- volume production September 2009

Also Coming soon...
- "PeterPan" – Authentic Rhodes Peterson Stereo Vibrato with active EQ and suitcase cabinet simulator
- Authentic reproduction Rhodes tonebar grommets

Stay tuned to //www.keyboardcottage.com over the next few weeks for details!  (Website is currently in development, so we are a bit behind on it right now.)

The schematic for the power amp itself on these late era home pianos is actually the same as a 50W Janus (late suitcase) power amp (Haigler).  I have seen and repaired one, so my claim is accurate.  

The power supply portion (bridge rectifier followed by big filter caps) for the power amp is also *similar* to the Janus, but it uses some different parts.  The basic concept is the same, however.

As you know, there are Molex connectors on the power amp chassis and other stuff that go to the preamp, cassette recorder, and power switches, but I have never seen those schematics.  Based on your findings, it seems they were probably not published.  When I fixed one several years ago, I remember that it was simple enough to 'reverse engineer' and figure out where everything was going and what it was for.

Congrats on the nice find!

Almost right, bjammerz...    

As far as I know right now, the following is correct:

1965-1968
Silvertop with Mono Amp (by Jordan electronics company) Mono tremolo. Fender Badge.

1969
Silvertop with 4pin stereo amp by Peterson strobe tuners, nicknamed Peterson amp. Silver grill, 3 knob. Fender Badge.

1970-mid 1973 (mark I is actually the name of stage piano not overall vintage)
Suitcase piano with 4 pin square-end stereo Peterson amp. Silver grill, 3 knob. Fender Badge.

1973-mid1977
Same Peterson stereo amp but with 4pin round connector. Silver grill, 3 knob. It should also be noted there are about 3 different phases/configurations of updates on the peterson amp from 69-1977. Fender badge up until beginning of 1975, Rhodes badge for 1975-1984.

1977
"1st version" 5-pin stereo Haigler Preamp with EQ sliders as printed in the Service Manual.  Black grille cloth.  Apparently very few were made.

See schematic here:
http://www.fenderrhodes.org/ch11/fig11-1.jpg

Late 1977-1979
"2nd version" 5 Pin stereo amp designed by Bob Haigler at Fender, nicknamed "Haigler" amp. "Janus" refers only to satellite system. Black grill with EQ slider preamp. Silver faceplate for preamp looks like Mark 1.

See schematic here:
http://www.fenderrhodes.com/pdf/late-mark1-suitcase-janus1.pdf

late 1979-1982
"2nd version" 5 pin Haigler amp, but with black faceplate to match Mark II stage piano.

Same schematic as above:
http://www.fenderrhodes.com/pdf/late-mark1-suitcase-janus1.pdf

1982/1983
"Low Noise" Preamp designed by Paul Gagon with rotary controls and pushbutton for vibrato on/off.   It is indeed a lower noise design than the Haigler, but the vibrato circuit is different yet again...

See schematic here:
http://www.fenderrhodes.com/pdf/late-mark2-suitcase.pdf


I have seen and repaired all of these preamps, so I know they exist and the schematics are correct.  I originally thought the "1st version" Haigler did not really exist since I had never seen one.  I finally saw one in a '77 though.   It has a few design bugs (it works, but the stereo vibrato effect has too much overlap in the transitions from channel to channel due to the oscillator design and LDR config). .  The vibrato sounded so bad that I modified the circuit to match the "2nd version" schematic.  I have asked James to update my explanations on the service manual pages to reflect this, but he hasn't gotten to it yet.

Tim

Unfortunately Darrell passed away and is no longer with us...

The secret to using an opamp with a unipolar power supply is all in the DC biasing.  

One can bias an opamp running from one 9V battery with half the supply voltage using a resistive voltage divider.  Now,  the opamp's 'ground' reference is actually at 4.5V.  Blocking caps are used on the input and output of the signal path to allow for 'bipolar' signals... recentering them DC-wise around 4.5V for the opamp.

i.e.  a 440Hz input signal goes between +/-0.1V (referenced to 0V).  Input blocking cap recenters it for opamp around 4.5V, so it goes from 4.4V to 4.6V.  Opamp gains it by 10x, so the output is now going from 3.5V to 5.5V.  It goes through another blocking cap and into a 0V referenced load (your power amp), which recenters the output around 0V , +/-1V.

One must be careful of the component values selected in order to insure the EQing is not affected.

Actually, the correct schematic is:

http://www.fenderrhodes.com/pdf/late-mark1-suitcase-janus1.pdf

I have never seen a 'Janus' preamp with the schematic shown in the service manual (and I have seen many).  The board layout depicted in the service manual actually matches the schematic listed above... NOT the schematic in the manual itself!

I think the wrong version may have ended up in the Service Manual.

Seems like your vibrato oscillator is probably not working.  Possibly a bad cap (C3) or the opamp (U2) in the schematic I listed above.  

Good luck,
Tim

Actually, the BBE process affects EQing very slightly as well as phase information vs. frequency.  

The Major Key Harmonic Clarifier uses a BBE IC, which is basically a box of programmable opamps configured as filters and gain stages when hooked to the appropriate external components.

'Lo contour' is more or less a bass tone control that boosts the lower frequencies (EQ). You can set this to your liking.

The 'Process' control enables the phase delaying characteristic to start taking effect.  Lower frequencies are delayed very slightly as compared to higher frequencies.  As such, the higher frequency information in a given signal reaches your speaker and ears BEFORE the low frequency information.  This results in us hearing greater clarity in the sound.  There is also a tiny bit of EQ boost added to the high frequencies.

To put it in perspective, if you play a note on your piano, the high frequency content and 'bell' like 'clink' sound of the hammer hitting the tine actually makes it to your speakers a slight bit faster than the fundamental part of the tone.  i.e. the upper harmonics get to your ears faster than the lower harmonics.

So, it is not pure EQing, but also altering the phase information of a signal that gives the BBE process its unique effect.

Tim