Case #1 sounds similar to my recent fix, lights but no button action, key sound.
After verifying the supply voltages, check IC33 and IC34.
In my case, the unit was stored standing upright, and the batteries were left in. The cells leaked, and acid dripped onto the main board and ruined the chips along the edge.
Look for corrosion on the ic legs in and around this area.
These chips buffer and demux the keyboard and button signals.
best,
-heath
--- In korgpolyex@yahoogroups.com, Michael Hawkins <korgpolyex800@...> wrote:
>
> First, how do the power supply voltages look?
>
>
> Mike
>
>
>
> ________________________________
> From: Malte Rogacki <gacki@...>
> To: korgpolyex@yahoogroups.com
> Sent: Thu, December 31, 2009 4:15:52 AM
> Subject: [korgpolyex] Trying to fix two broken Poly-800
>
>
> Hello everyone;
>
> new group member here. I've recently aquired two non-working Poly-800 which
> I'm trying to repair now.
>
> #1 is an "inverted" model, without a battery on the main board (but with
> the solder pads for it) and without a KLM-601. #2 has both the battery and
> the KLM-601.
>
> #1 occasionally powers up so that the display lights up; however it doesn't
> react to any button presses and makes no sound. About 50% of the time not
> even the display works.
> I've observed RST 5.5, 6.5 and 7.5 and they look pretty normal so far. What
> somewhat irritates me is that the CPU clock looks more like a sine than
> like a rectangle. Is this normal?
>
> #2 seems to have a problem in the RESET circuitry; pin 36 of the CPU reads
> only around 1.9 volts which I believe is not sufficient. The CPU clock
> looks more or less "sinusy" here as well.
>
> I would be most grateful for any ideas how to get them running. Right now
> I'm planning to move IC40 from #1 to #2 to see if that helps things with
> the RESET line.
> The material in the files section of the group has already been of major
> help here.
>
> Thanks and best regards,
>
> --
> Malte Rogacki
>