Sorry, but eventually this will help someone - or just me I guess. I found a CS60 KAS board diagram and SUB board diagram...
So: Someone had jumpered TU to the EK 2 connection on the KAS board resulting in 0 volts to the 26700 chip octave 4 pin. I removed the jumper and soldered that stray brown wire there and now have 6.46 volts there measured against ground. The CS60 tuning procedure calls for +4.000 volts. Adjustment is via VR14 on the SUB board, but a CS50 doesn't appear to have a VR14, it goes into IC3. In another manual, with procedures for all three, it says TU is adjusted with respect to E on the KAS board via VR11 on the SUB board to give +4.000. I get -6.46V measuring TU with respect to E on the KAS board, and adjusting VR11 on the SUB board has no effect on this voltage. Time to read up a bit I guess, maybe a bad capacitor?
Input would be greatly appreciated, but trudging on anyway!
Matt
--- In yamahacs80@yahoogroups.com, "velomatte" <velomatte@...> wrote:
>
> Update: VR1 - 4 adjustments made on the power supply. Was not much out in any case ~.02V + or - in most cases. Because I don't know: just because I have the correct voltages after these adjustments, does it necessarily mean my caps are good, or should I still just replace them.
>
> While proceeding to step 2, the TU voltage on the KAS board, I found a disconnected wire. It's a very fine gauge brown wire right by the red TU jumper wire. I tried to trace it but it disappeared into the main harness. Several of the soldered points near the TU look like they could have had a wire attached at one point. Anyone know there this goes? I can't find a good circuit interconnect diagram for the KAS board. Does someone have one?
>
> Thanks,
> Matt in Oakland
>
> --- In yamahacs80@yahoogroups.com, "velomatte" <velomatte@> wrote:
> >
> > I dragged a cheap unloved CS50 home today. I made sure it had all its voice cards - it does (even has a lid and it's legs!), and I was able to plug it in and get some sounds out of it with some borrowed headphones. I can play four keys at the same time -so it seems all voices are trying to work -but it sounds bad of course -tunings are all over the place. I haven't done a methodical inventory of functions, but most of the controls seemed to have an effect on the sounds it was making.
> > I've seen a lot of 'I'm working on chip two on board three to restore function x' posts on here, but didn't find one about starting from scratch nursing one of these back to health. I'm thinking a good place to start would be to borrow an oscilloscope and go through the calibration procedure.
> >
> > The reason I'm posting here: is there anything I should look at/check before I do the calibration?
> >
> > Does anyone have any cosmetic leftovers from a parted out CS50? Contact me off line.
> >
> > Matt in Oakland
> >
>