Vintage Synth Repair

Guys were over recording from Portland and this thing wrecked the last session here.  hehe.  Hoping we can get it up before they leave.  

The problem is the schematics on a rev C are different from the ones I downloaded with the LM317 in the PS.  THis one had a center tap on the in for one thing instead of the lower side of the transformer grounded in the diagram.  There are 7805's and a 7905 and one 5V reg has an extra heat sink attached. It was getting real hot so I replaced it.  The voltages are ok but there are still no lights!  And it still warms up though diode check to ground shows only .9V drop which seems fairly normal.  1.4V on second 5V reg w/out heat sink.  Can anyone help with

1) A rev C diagram?

2) you've seen this problem before?

Battery died i think prior and he lost patches.  2.5V on battery but that isn't going to kill the lights right?

--- In vintagesynthrepair@yahoogroups.com, "Robert Weigel" <sounddoctorin@...> wrote:
>
> Guys were over recording from Portland and this thing wrecked the last session here.  hehe.  Hoping we can get it up before they leave.  
> 
> The problem is the schematics on a rev C are different from the ones I downloaded with the LM317 in the PS.  THis one had a center tap on the in for one thing instead of the lower side of the transformer grounded in the diagram.  There are 7805's and a 7905 and one 5V reg has an extra heat sink attached. It was getting real hot so I replaced it.  The voltages are ok but there are still no lights!  And it still warms up though diode check to ground shows only .9V drop which seems fairly normal.  1.4V on second 5V reg w/out heat sink.  Can anyone help with
> 
> 1) A rev C diagram?
> 
> 2) you've seen this problem before?
> 
> Battery died i think prior and he lost patches.  2.5V on battery but that isn't going to kill the lights right?
>
Battery voltage wont determine regular operation. Can you scope the power supply circuits and look for ripple?
Can you disable certain sections ( by pulling some cables) to see if the main circuits come up after?
If the +5 was getting really hot there MAY be a failed part on that circuit. How old are the electrolytic caps on that part of the power supply?

--- In vintagesynthrepair@yahoogroups.com, "Scott" <painintheamp@...> wrote:
>
> 
> 
> --- In vintagesynthrepair@yahoogroups.com, "Robert Weigel" <sounddoctorin@> wrote:
> >
> > Guys were over recording from Portland and this thing wrecked the last session here.  hehe.  Hoping we can get it up before they leave.  
> > 
> > The problem is the schematics on a rev C are different from the ones I downloaded with the LM317 in the PS.  THis one had a center tap on the in for one thing instead of the lower side of the transformer grounded in the diagram.  There are 7805's and a 7905 and one 5V reg has an extra heat sink attached. It was getting real hot so I replaced it.  The voltages are ok but there are still no lights!  And it still warms up though diode check to ground shows only .9V drop which seems fairly normal.  1.4V on second 5V reg w/out heat sink.  Can anyone help with
> > 
> > 1) A rev C diagram?
> > 
> > 2) you've seen this problem before?
> > 
> > Battery died i think prior and he lost patches.  2.5V on battery but that isn't going to kill the lights right?
> >
> Battery voltage wont determine regular operation. Can you scope the power supply circuits and look for ripple?
> Can you disable certain sections ( by pulling some cables) to see if the main circuits come up after?
> If the +5 was getting really hot there MAY be a failed part on that circuit. How old are the electrolytic caps on that part of the power supply?
>

Also, disconnect the battery to see if it's dragging the ckt down somehow

THanks but yeah it's 2.5V *without power* (I wasn't clear about that)...so it's impossible for it to be dragging anything down except the memory itself.  Sounds like John's guess is probably the one on this.  Handy when someone happens to have had a similar issue.  I'll try to get another chip in it
--- In vintagesynthrepair@yahoogroups.com, "Scott" <painintheamp@...> wrote:

>
> 
> 
> --- In vintagesynthrepair@yahoogroups.com, "Scott" <painintheamp@> wrote:
> >
> > 
> > 
> > --- In vintagesynthrepair@yahoogroups.com, "Robert Weigel" <sounddoctorin@> wrote:
> > >
> > > Guys were over recording from Portland and this thing wrecked the last session here.  hehe.  Hoping we can get it up before they leave.  
> > > 
> > > The problem is the schematics on a rev C are different from the ones I downloaded with the LM317 in the PS.  THis one had a center tap on the in for one thing instead of the lower side of the transformer grounded in the diagram.  There are 7805's and a 7905 and one 5V reg has an extra heat sink attached. It was getting real hot so I replaced it.  The voltages are ok but there are still no lights!  And it still warms up though diode check to ground shows only .9V drop which seems fairly normal.  1.4V on second 5V reg w/out heat sink.  Can anyone help with
> > > 
> > > 1) A rev C diagram?
> > > 
> > > 2) you've seen this problem before?
> > > 
> > > Battery died i think prior and he lost patches.  2.5V on battery but that isn't going to kill the lights right?
> > >
> > Battery voltage wont determine regular operation. Can you scope the power supply circuits and look for ripple?
> > Can you disable certain sections ( by pulling some cables) to see if the main circuits come up after?
> > If the +5 was getting really hot there MAY be a failed part on that circuit. How old are the electrolytic caps on that part of the power supply?
> >
> 
> Also, disconnect the battery to see if it's dragging the ckt down somehow
>