Vintage Synth Repair

O.K.
So it sounds like it does have a negative power rail.

I would check the voltages before doing the cap thing.
Find a dual opamp and check pin 4 (-15v) and pin 8 (+15v).

See if they are there.
I would be concerned about the input IC's.
applying 24 volts,  + or - would not be good.

Let us now what you find.
GD



--- In vintagesynthrepair@yahoogroups.com, "b3nnysf" <b3nnysf@...> 
wrote:
>
> hey GD,
> 
> funny meaning sound comes out, buzzy, with a clean signal mixed in
> when you "add" with the clean signal knob... the effected signal is
> buzzy and not responding to the controls... the leds do power up 
and
> function normally.... maybe the power regulators are fine and 
there's
> a blown cap... I'll try that cap (possibly dead, it shows 
conductance
> with a meter) first and report back.. I just was asking because I 
read
> on the analog heaven archives that somebody once replaced the
> "negative" power regulator and it starting working again, however 
mine
> powers on fine it seems.... hmmm, dunno. Is there a difference 
between
> a positive regulator and a negative one? man, I feel lame for 
asking
> that.... heh! it takes a +24v and -24v on the power connector. I 
have
> the correct power supply, provided by www.studioelctronics.biz in 
LA
> for a whopping 200$... same company quoted me 600$ to service the
> unit. obviously I dont want to spend this if its a simple blown 
cap.
> I'll just do it myself. help needed!!!
> 
> thanks again,
> ben
> ..
> 
> --- In vintagesynthrepair@yahoogroups.com, "gerryrdahl"
> <gerryrdahl@> wrote:
> >
> > What do you mean by funny?
> > Also do you have the pin out for the power connector?
> > What is the external power supply voltage?
> > It may not run on a negitive voltage.
> > 
> > The more info the better.
> > Thanks.
> > GD
> > 
> > --- In vintagesynthrepair@yahoogroups.com, "b3nnysf" <b3nnysf@> 
> > wrote:
> > >
> > > Hi, 
> > > 
> > > I have a Marshall Time Modulator that is hurting-- (it got 
plugged 
> > in
> > > upside down) -- and its acting funny. I was wondering if any 
of you
> > > guys have one and could quickly tell me what the two power 
> > regulators
> > > are on the right hand side...I would greatly apreciate it.
> > > 
> > > I know that the one on furthest right is marked 340t -- this 
is a 
> > +15v
> > > regulator? and in mine there's a 7805 +5v regulator to the 
left of 
> > the
> > > 340t.... 
> > > 
> > > Isn't there supposed to be a negative regulator? help is 
needed,
> > > thanks in advance!!!
> > > 
> > > later,
> > > ben
> > > ..
> > >
> >
>