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Hi :-)

Hohner Electra is allways without tremolo....



Jenzz

Just to correct this:

Mutron Phasor (1) uses OTAs
Mutron Phasor II uses LDRs / LED


Jenzz

Hi :-)

I would highly recommend first to pull out the 2 power amp boards and the preamp voltage regulator board and resolder all Molex PCB connector pins.

Because of their thickness, there was often not enough heat distribution during the wave-soldering process, causing cold solder joints here.

...looks something like this:

https://vinatronic.com/blog/cold-solder-guide/


Jenzz

Hi :-)

The 54 circuit is a little different... The Tone control acts more like on a guitar. Since all pickups in a 54 are in series, the tone slider connects the 47 nF cap more or less in parallel with the pickups coils, forming a variable resonant circuit.

Jenzz

Hi :-)

There should be 4...

Allways two speakers per channel in parallel... giving a total of 4 ohms per channel, which is correct.


Jenzz

Hi :-)

Not every piano has them, these are mostly seen on MK2's.

These are there to support the harp cover in the middle to avoid bending if you put another keyboard on top.


Jenzz

Hi :-)

See the different profiles and dimensions, esp. from the axle center to back of the bar:


Old version: 57 mm

New verion: 66 mm


Keep in mind that the old version needs a center pin (hence the hole in the middle of the bar), otherwise it will bend when the pedal is actuated.

regards, Jenzz

Hi :-)

Seems that there is a bad ground connection on the right end of the pickup rail. The black wire comming from the RCA jack should be tied to the same screw were the red wire goes off to the 1st pickup on the right end.

The aluminum foil at that point seems to be not connected.....


Jenzz

Hi :-)

If you wind the pickups yourself, you might could incorporate a sort of extra winding in each of the bobbins only for the hum canceling.

This came to my mind as i remember the Bartolini Bass pickups for Music Man Stingray basses. These feature a 3-coil concept were the middle coil has no magnets, only to pick up the hum and do the canceling by the way was it is connected to the other two coils.

Jenzz

Hi :-)

Interresting project !

There are two things that came to my mind: I think all magnets should be facing the same magnetic (sounth) pole. Otherwise, the magnetic fields cancel out at the turnover points, resulting in loss of fundamental tone for these strings.

A humbucking effect can only be achieved when both coils 'see' the same amount hum /magnetic field, so the inverting coil configuration can cancel out the hum and leave the signal intact. Due to this, both coils should be as close to one another as possible (hence the configuration on humbucking guitar pickups).

Jenzz

Hi :-)

The plug should be diconnected when not in use, otherwise the battery gets drained.

The circuit draws roundabout 1,5mA, 9V battery has roundabout 500mAh capacity...


Jenzz

Hi :-)

You only need one conncetion....

Connect the Piano the the Janus that is supposed to be the master.
Connect 'Master out' of the master Janus to 'Slave In' of the second Janus.

Then you should have stereo with both speakers on on each Janus.

Each Janus is a stereo system in itself. If you have only one Janus and the Piano connected, the signal is panned between upper and lower speaker when tremolo is on.


regards, Jenzz

Hi :-)

Safest way is to leave the Piano and amp grounded and use a Line-iso-box for the audio connection. This way, both grounds keep sepatated.  Palmer 'Wupper' or Radial 'StageBug' will do.


Jenzz

Hi :-)

What happens when the amp is disconnected?

On a Wurlitzer, signal ground is connected to earth. On most guitar amps, its the same. As a result, both grounds are connected via the earth wire.

If you plug the Wurlitzer into the amp via audio cable, the shield inside the cable will close the ground loop, causing probably hum.


Jenzz

Hi :-)

Is the Piano connected to any other gear / Amp?

There sometimes connections that will form an internal ground loop. Avoid the connection on the right end between the chassis plate and the harp. This connection is already established by the shields of the wire harenss going to the preamp PCB on the harp.

Jenzz

Hi :-)

The drawings are right, this is the way its supposed to be.

You should have 3 different sort of springs:
Stiff (mostly marked with yellow spray paint) on both tonebar screws for the bass range
Medium (plain) on both tonebars in the midrange up to the right harp bracket and 'pickup-side' of the treble tonebars
soft (mostly marked with blue spraypaint) for the 'Keyboard-side' of the treble tonebars.

In some cases, the first 4 tonebars right from the right harp bracked will have medium springs on BOTH screws. The intend seems to be because these 4 tones use the somewhat softer white hammertips.

The average distance between the bottom of the tonebar and the wood of the harp should be 9,5mm (= thickness of the square tine bolt). Looking at the pic, most of them seem to be too low.

Jenzz

Hi :-)

All of these transistors will work (watch for different pinout!), but since this is the first stage, a low noise typ should be the choice. I would recommend MPSA18 or 2SC1845 for the first stage (again, watch out for different pinout)....


Jenzz

Hi :-)

Since the input buffer (T1) stage draws no significant current (not voltage drop accross R12), i think T1 will be damaged.

I would also recommend the change C11 (filter) and C6 (feedback). Electrolytic caps of this age are prone to high leakage, loosing capacity or being shorted.

Jenzz

Hi :-)

Did you check the cable from the RCA jack going to the pickup system? What about the voltage directly at the pickup electrode? Remember that there is an additional 10Meg in series, so voltage reading will only roundabout 70 V.

Since you have a good signal when plugging into the phono: Do you obtain the marked 12V at the collector of T1 ?


Jenzz

Just took some voltage readings.  I'm getting 150V where I should be getting 180 (on the other side of R1).

Any ideas on how to fix this are greatly appreciated.

Thanks!

Hi :-)

This is quite normal. Keep in mind that the 180V voltage is fed via a 2M2 (42) resistor into the last cap (44).

If you connect a multimeter, the input resistance of the multimeter (10Meg in most cases) will form a voltage divider with this 2M2. The result will be a roundabout 150V reading at C44.

Jenzz

Hi :-)

Since your Suitcase is from 1980, chances are that you have the preamp version that produces some kind of 'faint tremolo' even when tremolo is switches off.

In the former preamp version, the switch disconnects the LEDs in the photocouplers from the oscillator and cuts off the LED at the panel.

In the 2nd version (like yours), the switch only cuts off the 'intensity' pot and the LED on the panel, but the  photocoupler LEDS are still runing. Due to the circuit itself, this will produce a faint tremolo, which is more prominent over headphone than the cabinet (hence that both speaker channels work in the same box).

Jenzz

Hi + Welcome :-)

The pickups with the white band are prone to failiure. The laquer on the copper wire gets / is broken at the sharp edge of the bobbin (green circle in attached pic)). Due to the broken covering, the copper gets corroded and the wire is broken.

Since on a 54 all pickups are in series, even a single dead pickup will have the whole instrument dead.

The only solution will be to replace or rewind the dead pickups. The keep (hopefully) the working pickups intact, place a drop of urethane laquer at the area at the circle to recover the laquer layer on the wire.

Jenzz

Jenzz

Hi :-)

Yes, this would help. But i would only change up from B1 (the hard blacks and the wood core tips in the treble range), not the whole instrument.

Jenzz

Hi + Welcome !

Since the Hammertips are harder in the upper range (there a 5 grades of hardness on a Rhodes), this is pretty normal.  Due to ageing and playing, the hammertips develop a flat spot on their striking edge, making them even harder.

This is most pronounced at the yellow / black transition (A# 1 to B 1), as shown in your video.


Jenzz

Hi :-)

The switches need cleaning. If all tone switches are off, the instrument should be silent.

Jenzz

Hi :-)

What about the cable you're unsing from the cabinet to the piano? Is it 4 wires + shield? Be aware that the shield should only be attached to the connector housing of the cabinet side, piano side should be open. Otherwise you get a ground loop.

Inside the cabinet, tie the chinch cable together and keep them as far away from the transformer as possible.


Jenzz

Hi :-)

The upper range is sensitive to striking line (take a look at the manuals, the glued hammer stems could have moved over the years, resulting in impropper striking line) and hammer hardness.

The felt covering of the hammers at the upper range is thin to get the neccesary hardness. The felt covering often has cracks and got puffed, so the hitting surface is too large and the hammer has become too soft to build up the enery. As a result, these notes are much quieter.

Re adjust striking line by applying heat to the glue of the hammer stem and move back or forth. This is try and error. There will be a position where the reed will respond best.

Jenzz

Hi :-)

Since it is an Mk2 and from '81, chances are that your piano frame was mounted into a case that was supposed to be for a plastic key Mk2.

The lip of the lower part of Mk2 cases for the plastic key models is roundabout 1 cm lower than on a case for wooden key Mk2.

So, if you mount (for some reason) a wooden key piano frame into such a case, you will have a space between lip and keys.

Jenzz

Hi :-)

Do you have both + / - 30 V from the power amp power supply (the 2 big caps)?

Check or replace the 1uF cap (C2) across the offset pot. If it fails / shorted, the output is totally out of DC balance and full supply voltage can be seen at the output. Had this issue on some Suitcase Amps in the past....


Jenzz

Hi :-)

I can't hear any undertones, just the normal intermodulation that you get when playing certain intervals (which is normal on a Rhodes).

Is this a miked sound from an amp?


Jenzz

Great review, thx!

Jenzz

Hi :-)

The additional cap is original on an 88 piano. It forms a high-pass for the last upper 12 notes.

Do all of the upper 12 pickups work?

You cannot view this attachment.


Jens

Any transformers nearby?

Remember that the aliminum foil will only shield against static / capacitive coupling, but not against magnetics...

Jens

Hi :-)

Did you plug directly from the harp RCA, while having all other connetions (preamp) disconnected?


regards, Jens .-)

Hi + welcome :-)

Give it a try to connect the damper bar to harp ground. The damper bar is electrically floating, since the axles are running in those nylon bushings. All noises that the bar recieves are then capacitive coupled into the pickups, which are right above, esp. on the bass side.

The older models had such a connection right off the factory...


Jenzz

Hi :-)

Remember that you will allways need some force to lift up the damper arm. The damper arm is spring-loaded, so maybe you could reduce the tension there a bit. The drawback of this is that the damping itself will be not that instand / accurate as before.

Jenzz

Hi :-)

There are some interresting pics from the inside Mk8 at NAMM on the german 'Musikerboard'...


https://www.musiker-board.de/threads/namm-2023-the-transition.740533/post-9502871



Jenzz

Hi :-)

You have to cut the sustain dovel down to lenghts of that of a stage piano, then insert this guide cup:

https://www.vintagevibe.com/products/fender-rhodes-sustain-guide-cup


Now you can use the normal stage pedal...


A hotfix will be to drill a hole to the bottom of the dovel to fit the size of the pushrod.



Jenzz

Hi :-)

VV felts are harder / more compressed than the originals, you did nothing wrong....

Jenzz

Hi .-)

Looking at the pics, it seems that the leads of the diodes have melt into the housing of silver caps, probably touching the inside foil?

Jenzz

Why not using the old / original screws?


Are they the thick ones (4,2mm) or the thin ones (3,45mm) diameter below the head?


Jenzz

Hi :-)

You should change these fuses to the standard 5x20mm + holder. You can use 1,6A (which is the nearest type in EU) slow-blo. Since the voltages are not high, voltage rating doesn't matter here.

Jenzz

.... i figured it sounded very much like my behringer vp which is a clone of the small stone, really need to buy the real deal at some point,

Hi :-)

I would give the VP an try...

Look for the the Moot Booxle video on YT where he compares the VP and a V3 Small Stone. I think the VP sounds 'spot on'.

Jenzz

Hi :-)

Sounds pretty much like a vintage EHX Small Stone Phaser with color switch in 'Up'-Position... And some volume tweaking...

Jenzz

Hi :-)

This problem in very common. You need a Line-Iso-Box.

The Wurlitzer's signal ground is tied to the pianos earth connection (3-prong connector).
Mostly all tube amps do the same, signal ground is tied to earth (for saftey reasons / High-Voltage).

If you connect a Wurlitzer to a tube amp, you will close the ground loop via the shield of the audio cable.

So, you need someting to 'isolate' the signal path's ground. This can be done by a line iso-box (1:1 audio transformer)... Palmer PLI-01, PLI-05

Jenzz

Hi :-)

The diodes have to handle the current of the power amp, so i would recommend something like the 1N5401 - 1N5407.

Jenzz

Hi + welcome :-)

Keep two things in mind:

The 5 hignest notes have no dampers, so there will always be some kind of 'faint ringing' when notes are struck.

When the pedal is released, all reeds are bend a bit downwards due to the tension of the sustain / damper arm mechanism. When you hit the pedal hard, the releasing damper felts will pull away from the reeds, causing them to ring because of their own bending tension.

The, this phenomenon is kind of normal to some degree.

Do you have a sound file?

Jenzz .-)

Pre-tuned doesn't mean 'exact'.

This is why i allways sale pre-tuned reeds a bit too low.

The machining seems to be more precise on the older models up to the 200... The worst machining is on the german models 201 / 300... It seems to me that the B-Stock parts were sent over here ;-)

It's the experience from over the years and what i see / measured here in the workshop... Maybe different from yours.


regards, Jenzz

Hi :-)

This is common due to the age of the piano. The pedestal felts and/or the key rest felt will be compressed to some degree over +45 years. I personally would leave this as it is...

The miracle mod doesn't adress this issue, it changes more of the overall feel of the action.



Jenzz

It would appear my balance rail is tilted back quite a few degrees. I'm not sure what to do about that. Any help would be greatly appreciated.

Hi :-)

This is pretty normal and the way its supposed to be.

See this pic from the manual:

You cannot view this attachment.

Jenzz