Good questions.
Power supply has been recapped, new regulators, etc. I replaced the 4000 CMOS ICs on the TKC board. The synth was playing, but I was having weird problems like 1 voice would continue to sound (but I could still trigger new notes). I had been testing various cards trying to solve that problem and discovered a few wires had broken loose from their solder positions.
The last round of testing - I had all the wires correctly soldered (they matched the color and positions in the service manual) and one of the lower boards (KAS, SH, TKC) shifted at some point and blew the 500mA fuses in the PS. I replaced the fuses, checked for obvious shorts (didn't find any), powered up without the large connector (I jumpered the +/- 15 and sense lines as stated in the docs) and checked all power supply voltages. They are all correct. I plugged the large connector back in, pulled the sense jumpers, and powered up. Voltages through the entire synth are correct and stable at all the boards. However, now I get no triggering of voices.
--- In yamahacs80@yahoogroups.com, Csaba Zvekan <czvekan@...> wrote:
>
> Hi ,
>
> Let us know what has been done/restored previously to this particular YAMAHA CS-80 ? Are the original 4000-Series CMOS chips still in there ? Have you started replacing some capacitors, yet ? How long have you had this machine ? Has it ever played (I mean while you have it ) ?
>
> Csaba
>
> On Apr 18, 2010, at 4:46 AM, tmoravan wrote:
>
> > OK - time to yell for help.
> >
> > Cleaning up a CS-80, and there's no voices sounding when playing a key. Started debugging at the KAS. All power looks good, note values are registering. Nothing appearing on the trigger outputs. Going backwards, the U1 -> U5 are mostly pegged at 8.48v and do not change no matter where on the keyboard I press.
> >
> > Is this a dead YM26600, or is there something else causing this?
> >
> > While I'm here, what should the clock input on pin 2 really look like? I'm not really seeing a stable square wave kind of oscillation there.
> >
> > thanks
> >
> >
>
>
>
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