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Is there a documentation on what the DC and AC levels of the 80W suitcase (Peterson) preamp are?
What is the maximum input level before distortion? What is the overall gain?

I simulated the preamp in LTSPICE and found that the maximum input level before distortion is about 400mVpp
and the gain (1KHz, Vol. pot in max. position, tone control pots in mid position) is about 5. 

Is there a documentation on what the DC and AC levels of the 80W suitcase (Peterson) preamp are?
What is the maximum input level before distortion? What is the overall gain?

Now I'm a bit further. I powered the amp first time. It was stated that the amp worked. I measured the DC voltages and it turned out though +/- 35V were fine (37V, but that was with no modules connected), the 25V were not there, just 2.4V and no reaction when pot got turned a bit.

2N3392 ok, DELCO 020725 measures C/E short. Now I'm asking for equivalent.

Thanks. Difficult to find a direct link to the schematics. I found a large PDF "Rhodes Service Manual" elsewhere (don't remember where I actually got it from) P/N 34-0119-000 and there on page 11-14, 11-15 is something called 80 Watt Suitcase, Peterson Design.

This looks like it fits the hardware I have here.

I'm trying to understand the circuit diagram. In Figure 11-9, upper right corner, there is a signal (collector of 2N3591) that is designated "From Power Supply". Where does it come from or go to?
(just to understand it). Is there a diagram showing the cabling between the power module(s) and the power supply/main panel?

I have the innards of a suitcase piano in front of me. My job is to inspect and potentially repair it.
I know Fender Rhodes stage pianos and also remember to have played on an 88 suitcase couple of years ago.

What I have here are the following pieces:

a Preamp with three pots. One of them seems to have a pullable axis.

2 power amp modules, each having a cinch input

I'm attaching a photo of the front panel. The P.T. is 230V already. The Euro C13 plug has been added by me (3D printed adapter).

Indeed it carries an ,,FR", though not sure whether it's a 7055. Will verify.

To complete the information:

The MOD.-field carries an "FR", the AMP.-field is ampty, er, empty. In the u.r. corner it says P/N 006625.
 

Indeed it carries an ,,FR", though not sure whether it's a 7055. Will verify.

Many thanks for the clarification. Good to know that it's originally built so and not some modification someone did in hindsight. It's a "rhodesworks" ("Baustelle" we say in German) on the other hand. One missing hammer mechanics, one broken tine, unevenly levelled keys.Missing legs, worn tolex, broken hinges and clamps. But it's managable, I think.

Since you pointed me to "KMC-1" now, I set out to look for pictures or occurences of that KMC-1. So far I only found it in a version built on a heavy upright piano lookalike support or foundation.

Could it be that mine was taken out of such a piano and been put into a Mark I case? Or were these KMC-1s also built into portable cases?

The other peculiarity with this instrument is, that it has a wooden music rack rail attached to the black cover.

Recently I acquired Rhodes piano that was showing a somewhat unusual logo but it didn't look as if it was not original in any way. I'm attaching photos. Maybe someone can comment.

IIRC, the front legs of a seventy three have aluminum plugs pressed in the leg tube. Some spare part suppliers are offering round black plastic furniture plugs.

Does anyone have the exact measures of the inner resp. outer diameter of the leg end tube? I'm about to turn these on my turning lathe.

EDIT: meanwhile I had the opportunity to measure the leg tip myself. It's 16mm outer, 13.2 mm inner diameter.

Jenzz,
although the idea of reversed poles is an interesting point,
I did a test with a compass and the magnets are in sync.

Thanks, Sean, for your comments. I'm attaching my hand crafted tuning file for Tunelabs pocket Tuner (Windows Mobile) from the stretch tuning chart (which covers the full '88 range). Maybe it fits their newer versions for Android and iPhone. They also have a notebook version for Windows 10 (11?). The attached file has to be renamed to the extension ".tun", when being used with the tunelab program.


--
Christoph

I'm intoning a 73 MK I and find that the lowest E (E1) doesn't sound as fat as its right neighbor "F" is sounding. Could it be that it is because the E1 doesn't have a pickup magnet left of it?

Is it documented somewhere what the typical distance between tonebar and the shelf should be? That is, how far the springs should be "squeezed" down?

I see that the more you squeeze them down the better the hammer reaches the tine when playing with low key stroke force.

EDIT: Found this documented in the manual as "escapement adjustments"

Nonetheless, is there a way to influence the hammer action? I'm noticing some hammers not hitting the tine when actuated with low force.

I'll be answering my own question:

first off, I found a way to edit a .tun file and craft a stretched tuning file. I can publish it here but there doesn't seem an interest yet here since probably not many do tune a Rhodes using tunelab. Anyway, what bothers me more is a statement coming from the makers of tunelab when I asked them whether a tuning file for the Rhodes 73 exists:

"A Fender Rhodes doesn't have any inharmonicity like a piano, so there is no need for stretching."

As an owner of the tunelab piano tuning program I'm curious to know whether there is a ready made tuning file for the Rhodes piano available somewhere?

Could possibly make one from an equally tempered file. Looking at the tuning chart in the service manual, I see stretching down to the bass and sretching up in the highs to max. +-30 cts. Actually there are three curves. What do they mean? Is it a choice one has?

Anyone out there using tunelab?

Thanks, Sean, for the support in finding the device. Digi-Key do a good job in supplying comprehensive information, datasheets etc., albeit awkward and expensive when it comes to buying single quantities.

Besides that, do others observe this subtle influence on volume with vibrato switched off? And what do you think of replacing the vibrato shut off circuit by a double switch, one switch for the indicator LED, the other for cutting off the steering voltage to the Vactrol cell.

My power supply is a lab supply at the moment so this is definitely not the cause. With the 100 Ohm resistors is it quite normal that there is a drop in PS voltage but this drop is being suppressed by the opamps anyway due to their PSRR.

One can easily see that with S1 to GND, die LDRs are still steered thus leading to the still noticeable volume change.

It is probably possible to shut down vibrato totally by turning speed to 0Hz.

Another circuit change would be to use a dual switch and cut the wire after R39. This would mute the LDRs totally.

But where does one find such a nice Knitter switch with that flat shaped lever?

Thanks, Sean. I could identify the second circuit diagram being close (but not identical) to the PCB layout I have (see uploaded photo in the other thread). I may be blinded but I cannot figure out R39 in that 015243 schematics either. Mine is P/N 105244.


Oops! Found it. Going from junction of CR1/CR2 to pin 7 of U2B/R26.
Ok. Now I can be sure to have the right schematics.

--
Christoph

Foto posted.

Sean, I now saw that you had mentioned the newer (reviewed) schematics in your other post .

That one fits my PCB layout (REV A).

Ah, I understand. Your stress laid on "not smooth". Yes, that's due to the rectangular character of the vibrato voltage, a bit smoothed at the edges.

I noticed that my amplifier is REV A and the circuit diagram in the Fender Rhodes manual doesn't match the PCB layout there. R23 is 1K, R39 not present in the schematics.

--
Christoph

deleted

Christoph,

The stereo tremolo is not a gradual swell from side to side, it is a surge in volume that switches back and forth (with some subtlety provided by the intensity knob).

...

Anyone that has actually had a Janus preamp with sliders on their bench care to speak up?

Sean

Just want to mention: the Vibrato *is* anti-phase, thus providing a panning effect (you may  call it stereo)

In the video I've uploaded one can see the antiphase vibrato as well as the problem. It starts with vibrato off, inmidst I switch to vibrato and after that I switch it off again.

I found that the amp (coming from an 88 suitcase) I have here for inspection shows some unwanted effects with vibrato.

I found that the output signal is still changing volume also when the vibrato switch is in the off-position.
When vibrato is "on", the amplitude change isn't really smooth, it's kind of jumping.

Is this normal? Could the LED-Photoresistor units be aged?

While being at this 5pin  amp and although this thread is two years old, I'm asking it here:

I have  this amp here for inspection. Don't have the power supply here. Can I assume that the supply is +-15V?

—
Christoph
P.S.The amp has two slide pots for treble and bass,Vibrato Intensity/Speed knobs,Volume knob,
Accessory 1and2, which seems to serve as an effects loop in/out, if I interpret the above  circuit diagram correctly.
U1, U3 are RC4558P
U2 is CA1458G to answer the O.P's question.

DMI Most likely represents Dallas Musical Instruments (formerly Dallas Arbiter) in the UK. They also made Sound City guitar amps and these photos do look very simillar to guitar amps around that time.

Thanks for the information. I remember "Sound City" from the sixties . Would be great if I can find someone from the engineering staff today who can offer circuit diagrams. Otherwise I'm left to reengineer them (which I'm half through anyway)

--
Christoph

Seems to be a rare or little known device, since it is UK made. Maybe anyone from UK in this list might know the company who made it:

DMI (UK) LTD  FARADAY GROUP OF COMPANIES 2x50 WATT

is imprinted on the PCB bottom face.

I couldn't find much about a company named DMI and having to do with electronics in the net.

I was already able to get rid of the noise by resoldering every solder spot on the power amplifier board finding two blatant cold solder joints.

Possibly I could make the amp working again without having a circuit diagram. But it is always annoying to "work in the dark" and I'll probably try to reverse engineer the schematics unless someone comes up with one here.

--
Christoph

I'm in search of schematics for the so called "English Club Model", an 88 with built in power amp and preamp.

Preamp is totally noisy and I'm trying to give it some care.

Anyone knowing a source for the schematics?