studio 440 powersupply probs

[nighthawk]

Dear Robert,

I have seen Op-amps pull down supplies like this.  While I haven't worked
on that model, I can give you some tips that are common to many units.

1: Try to isolate the supply.  If there is a ribbon cable going to the rest of the
synth, just disconnect it.  Check your voltages at the connector and make
sure you have what is supposed to be.  Don't worry about where they are
w/respect to schematic.  Just verify +/- 15, 5 VDC,  and ground.  If this is
where you have problems, check the filter caps & make sure none are leaking
electrolyte.

2: If problem is not in the supply, make sure grounds to all boards are good.
Another source of supply strain is bad ground and corrosion.  Make sure no
corrosion is on any of the connectors/ribbon cables/card edges/etc...

3: If you still have problems, feel around for any chips that are hot.  Generally
anything that loads down a supply like that is drawing current, and gets hot!

Hope this helps.  I occasionally need a schematic.  Wine Country has yours,
of course for $$$.

Jimmy Williams
----------
> Ok, heres the deal..
> the studio 440 outputs +/- 15v, +/- 5v...
>
> Both are too low.. 4.85 volts and 14.8 volts...
> The chips run HOT as hell in this machine..My first guess is that the
> powersupply rails are rippled.. The reset on the uP has trouble booting
> the system.. I fixed a jupiter6 with this problem, as well as a prophet
> 5 with uP reset problems.. it ended up being PS ripple from caps going
> bad..
>
> But, for SOME reason, Sequential WILL NOT give out the schematics for
> the powersupply, NOR will they work on a powersupply!
> Why not? I think this is somewhat ignorant of them to let soo many of
> these beautiful machines go down the tubes due to a powersupply!
> I want to ressurrect this unit, but can anyone think of any caveats?
> Perhaps the unit is some weird switch mode PS? I just dont get it..why
> all the mystery about this power supply?
> Any tips?
>
> Robert
>