Left channel of my MPC 1000 don't play.

Hallo boys, please help.
Can't solve serious problem with playback.
Left headphone channel and also left main output don't work.
I bought it friday on eBay last week. Seller is not willing for return as he said that everything was working fine.
It was eight days on the road through several countries, so it may happen something with it.
Here are brief facts:
I can sample stereo sound.
I can playback these stereo samples, if assign them to 1+2 or 3+4 assignable outs. These plays fine.
In left channel is only significant crack during boot-up. Otherwise is left channel silent.
Volume knob is in very good condition, it control volume of right channel smoothly and without cracking.
I tried two JJOS and original OS. Problem remain the same. Now there is actuall JJOS 3.16.
I removed top and bottom cover, and even removed board with headphone jack and card reader.
I try to find some disjoined ribbon connectors, but everything seems to be fine and clean without any dust or water damage.
Could you, give me a hint, where the problem can be?
Is here anybody, who have scheme of electronic circuits?

sounds like a problem with the board or cables connecting the board. Google MPC 1000 service manual and see if you are able to find anything online.

Since you're handy with a screw driver I'd at least take the top off and see if disconnecting/reconnecting the internal cables for the audio board might help. I forget how the L/R and HPJ are connected, but I doubt it's an issue with the CF/HPJ board.

If you're handing with a volt meter, you could check to see voltage levels and see if you can find where there might be a short in the circuit, and if you can find the short, you might be able to solder a new lead to fix it (assuming it exists).

You could also go to MPC-stuff and see if they have an audio board replacement... though without knowing where the issue is, this is not always the best course to take because it might be someplace else.

Hope some of that helps.

Many thanks for reply and your tips.
I lost patience and already sent it to service.
Once I get answer where the problem is, I'll post it here.
Cheers

Volume knob (potenciometer) connection on board was disjoined.
It happens probably during transportation.

Were you able to get it soldered for the repair, or did you replace the board?

The service man told me, that only connections was repaired.
The board remain the same.
Finding & repairing this issue cost approx. 23 GBP without transportation.
I let him do several another servicing (exchanging all buttons, memory card fix, cleaning sliders)
All together with transport I paid 80 GBP.
Now it feels like brand new machine.
I'm going to chop some old funk tracks!
ehmmm... I have to read that extensive manual before it, of course

Don't forget to get the Bible, it's full of great information