Kurzweil PC2x - no sound

[techineer]

I have a PC2x on the bench that is driving me nuts. It has no audio output, and no signal from the DACs. It passes all the diag digital tests (RAM, ROMS, etc. Keyscan diags show that the keys are recognized, and the MIDISCOPE shows that it is generating the MIDI events. Local mode is on.

Any Kurzweil techs out there that might offer further suggestions?


It originally came in with "Scanner is dead!" errors. After going about as far as I could at the component level, I ordered the main engine board. The new board arrived with different type connectors and I had to devise adapters to mate them up. At startup, the display went straight to "Install engine". Performing a hard reset returned to that point. After much difficulty, I finally got it to load the new engine OS, after which it still would boot to the Install Engine prompt. Diag tests showed ROM checksum fail. I reloaded the boot block, and the ROM checksum now passes, but there is still no audio output.

TIA...

[iannicholson]

Same here.

Did you resolve this problem? I have the same issue with my PC2X. Tried the manual checklist to no avail.

[techineer]

Wow... I don't recall. That was 10 years ago. If I spent money for an engine board, I think I would remember if I didn't get it working, but I don't recall the solution. I'll see if I can find my record, but I have my doubts.

[techineer]

I found it! I had posted to a group of techs (who weren't able to help), but I posted the solution I found just to document it.

Finally got it. Started poking around with the meter and scope on the I/O board. Decided to re-check the power supplies... yup, all good... wait, what's that 5Vref? check it.... Huh? less than a volt.... where does that come from.... (hunt, hunt, hunt...) Ah.. a chip inductor off the +5v line. There it is! 5v one side, 1/2 volt the other. Looks like it was a bit warm, too. Tried shunting it with the milliameter but no improvement. Tracked down another chip and replaced it. Put the board back in and voila! Sound! It was the reference supply voltage for the ADC. So the ADC couldn't read the battery. Not sure yet why it also blocked the sound signal.

[iannicholson]

Well that’s very encouraging! Thanks so much for the quick reply! My ADC looks like this, which I’m sure is not the factory standard...



I don’t suppose you remember the inductor you replaced...?

[iannicholson]

I found the service manual here (if anyone else needs it)

https://www.kevinchant.com/uploads/7...ice_manual.pdf