Yamaha CS80

hello
I need help for my GX-1.
both of KAS boards for upper and lower
keyboards have problem and now my GX-1 can not 
sound correct.

upper key keeps silence.
lower key, two octaves out of 5 sound correct,
however the others sound silence or strange.

YAMAHA here in JAPAN gave up to fix them already  
and my friend in sweden does not have time to help me.

sorry to bother this message board since it is for CS80.
I hope to hear from some analogue synthe lovers......

sincerely

Kenji 
YOKOHAMA city, JAPAN