Hammond XK-1 schematic

[HDSarge]

Does anyone have the schematic for this portable organ? I am looking for the output section that would show IC's U7-U10. I have the organ signal into U7 (4580), but no output from the unit. Power Supply(just 5V and ground) is good, volume controls test okay and the relay closes (also jumped it without improvement). I replaced U7 and U8, checked a bunch of 2.2uf blocking caps and smt resistors; no improvement. The phone # I have for Hammond is not in service. Seems simple, but I am missing something. Any help would be appreciated.

[Enzo]

I have not seen one of these in a long time, but it seems really unlikely to me the analogue outputs would run on +5 and ground. Especially multiple 4580s.

If they were, then pin 4 of all those ICs would be at ground, and pin 8 at +5, are those the voltages present AT THE IC on the board?

Are there no 12 or 15v supplies on the system?

[HDSarge]

There is a small smps with only +5v and ground. The digital section develops 3.3V from that 5V, but that is it for voltages. Pin 4 of the opamps is at ground, and pin 8 is 5V. It is unusual, which is why I would like to see a schematic. The 4580's outputs are at voltages between 0-5V(which makes sense), symmetric left to right sides,but different from op amp to op amp. As stated, I replaced two 4580's with no change in symptoms or output voltages. This is an smt pcb that is populated on twosides , I do not want to be replacing parts based on guesses.
I found that U10 (a higher current 4556) is after the relay and drives the headphones. No output there either,as it uses the signal that is missing. U8 drives the volume control to U9 which feeds the 5v relay leading to the output jacks. U7 is not clear to me, and that is the last place I can find a signal.
A schematic would be appreciated.

[Enzo]

Fair enough, live and learn.

I looked at the Hammond-Suzuki web site, here is the owner manual for it.

http://hammondorganco.com/wp-content...XK-1manual.pdf

near the end of it is a warranty registration form, and there is a phone number on it:

630-543-0277


I just dialed it, and after two rings it answered "Hammond Suzuki Company"

[HDSarge]

Enzo, Thanks for taking the time, providing the info, and confirming the phone #....that is very generous.

I was told that Hammond does not share outside their authorized network, but I will give them a call and take my shot, this is an old product.

Is there a keyboard repair forum similar to MEF?

Thanks again.

[Enzo]

I know there are synth forums, but I don;t know any of them myself.

[dmeek]

Here is the service manual

Doug

http://music-electronics-forum.com/a...1&d=1391112303

[HDSarge]

Good news for me, the Hammond is running again.

I called an authorized Hammond repair center, and although helpful, they were only willing to answer my questions while they looked at a schematic. My first question was about the odd +5V/ground supply for the opamps and they told me that that was the way it was done. I then asked about the biasing of the inputs to allow the single end supply and was told there were no resistors beyond the feedback from the output.
This was making less sense to me. In the meantime Enzo found, and verified, a Hammond phone #. I called and a very pleasant women said she could not provide a schematic, but had an e-mailable service manual. Anyway, I now have more XK1 info than I need and a full set of schematics.
The opamp page seemed to confirm the information from the service centers, but a block diagram showed a 5v/-8v supply to the opamps. There is an other way to measure ground on a supply line.....a shorted component. In this case a 100uf/16v filter cap on the negative Vout of a switched voltage converter IC.
Replacing the cap restored the supply operation (that chip most have some good internal protection).
Interestingly, the schematic has an error on this converter IC and does not show the negative V output.

Moral, solutions are usually simple, use all the help available, but remember you are the repairman. Keep a mirror handy when you want to toss some blame around.
Thanks again to Enzo, and the MEF....this one might not have been returned repaired.

[HDSarge]

Thanks Doug, that is the one. I do not know how to do attachments.

Using the manual from dmeek: on page 5 there is a block diagram that shows the 5v/-8v and identifies U43. Page 19 shows the opamps and U43, but pin 11 is not labeled with -8v it supplies, and no supply connections are shown on the opamps. C219 was the shorted cap.

[Jazz P Bass]

A switched capacitor regulator.
Huh.
http://www.ti.com/lit/ds/slvs033f/slvs033f.pdf
Page 2 shows the block diagram.
I would replace the input capacitor also.

[Jazz P Bass]

Page 19 shows the opamps and U43, but pin 11 is not labeled with -8v it supplies, and no supply connections are shown on the opamps.

Actually, if you follow U43/ pin 11, it goes through ZD7 & ZD4 as it makes it's way to opamp (U8 & U9) pin 4.

Not exactly clear as a bell, but the -8Vdc supply is shown.

[HDSarge]

Good eyes Jazz.
Before this is done, all the Zeners and caps around U43 need to be tested, the caps likely just replaced. Before replacing that bad cap, I measured a short, not a diode, from pin4 to ground. I am guessing that it is C220 that I replaced. Like many pcb's,things are packed in and the silkscreening can be hard to follow.
The owner left this organ in storage long enough that it went into "back up failure". That is the third level of battery warnings. If the owner agrees, I would like to replace the electrolytics.
This is actually a fun instrument, makes me wish I had better organ chops.