Vintage Synth Repair

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
..

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
> ..
>

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
> > ..
> >
>

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
> > > ..
> > >
> >
>

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
> > > > ..
> > > >
> > >
> >
>