I might have some CS50 specific docs at the workshop. Will have a look and
post up if I do.
I have a CS50 to go through myself in the coming weeks. So I'll be keeping
tabs on this thread.
As regards caps... If you've got a oscilloscope have a look at the voltages
coming off the power supply.
Set the scope to AC and see what the ripple looks like. You should have
minimum ripple ie. very low voltage peak to peak. if it's not less than say
10mV (not sure what the spec is for the power supply) then it's probably
worth recapping.
Also, a visual inspection will tell you if they're getting a bit old. If
the tops of the caps are bulging, or the plastic sleeving has shrunk back,
and of course if there's any kind of electrolyte build up on the
legs/corrosion on the pads/board.
Change for good caps ie. 105 degree operating temp. Low ESR if possible.
Voltage limit can be a little higher if needed, but not too much. I tend to
go with Panasonic or Nicihon when I can.
B
On Wednesday, May 29, 2013, velomatte wrote:
> ∗∗
>
>
> 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 <javascript:_e({}, 'cvml',
> 'yamahacs80%40yahoogroups.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 <javascript:_e({}, 'cvml',
> 'yamahacs80%40yahoogroups.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
> > >
> >
>
>
>
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