Vintage Synth Repair

Hey guys,


Fixed! I had the wrong power regulator in there... It was supposed to
be a LM320T-15, I had a 7805... oops I put a positive where there
should have been negative!

David Kulka of studio electronics.biz helped me with the diagnosis!

awesome vader sounds now!!

thanks,
ben
..






--- In vintagesynthrepair@yahoogroups.com, "gerryrdahl"
<gerryrdahl@...> wrote:
>
> 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
> > > > ..
> > > >
> > >
> >
>