korg poly 800 fixing

Hi guys,

I bought this 2nd hand poly 800 for 20 quid and have been trying to get it back to life. The led display doesnt light up but i traced that to a defunct transistor array driving the leds.

So, I turn it on and it makes a sound! the trouble is, the sound doesnt respond to the keyboard or any other controls and is always the same - rising pitch starting from 0hz and going to about 1khz!! The sweep takes about 20 seconds and stays at 1khz until i turn the thing off.. Could this be a broken cap filling up little by little? Could the microprocessor be dead? The good thing is, based on the sound it makes, the oscillators, filters and the chorus seem to be working.

Its my first synth restoration project so any tips on troubleshooting would be really warmly appreciated! What are good methods for testing the parts? so far I've just been looking for cold joints and measuring resistance across different points on the PCB so i can see if there is a dead connection..

Thanks guys!

It's been a long time since I put together my Poly800MkII out of two broken units, so I'm afraid I can't think of any troubleshooting tips for you at the moment. But good luck with it--It's a cool li'l synth.

You did do a reset, right? I also remember a factory mod involving something with the internal battery, but can't recall any of the details.

The Poly800 I got from a fleamarket was dead silent. Had to load settings by means of the tape-interface. This one of this thread seems to make more sound already, so that (tape-loading) won't be it I expect.

Good luck!

Hi!

Maybe this could help, schematics.
Good luck!

/Hampus