Vintage Synth Repair

No sound because no stored patches.

Put your oscilloscope on some of the VCO wave output
pins and see if there is an audio waveform there. If
there is, play some keys and see if the frequency
changes. If it doesn't, push the autotune button and
see if the VCO frequency sweeps as the auto tune
process occurs. This will tell you if the computer is
talking to the sample and holds, and if they in turn
are driving the VCO's. 

If you get that far, put your scope on the outputs of
the VCF's, and see if there is a signal there. Before
you do this make sure that you set up a basic patch on
the front panel with VCO's turned on, mixer up, no VCO
of VCF modulation, VCF cutoff open, resonance down,
zero attack and decay of the 2 ADSR's, and so on. 

If there is filter output, move on to the voice
channel VCA's, and finally the master VCA. The EQ
board is another common failure. 


--- fsimon100 <fsimon001@...> wrote:

> I truly had a great day. I replaced a 1Kx4 RAM and
> resolved my 
> computer problem on my P10. Now all LEDs light up
> and the unit 
> behaves somewhat functional. Upon turn on the unit
> goes to tune cycle 
> then all LEDs light up and entire panel is
> functional. Still no sound 
> but this is a great milestone. Two problems I see
> are sequential 
> board is dead which I think I'm on top of. This is
> PCB9 which I over 
> voltaged when I put the 12V regulator in instead of
> 5V (due to poor 
> documentation this is an option for tape or wafer
> drive). I think 
> this will be easy to fix but I was hoping to help on
> one clue. There 
> is a window showing voices 1 thru 5 and below 6 thru
> 10. The top 1 
> thru 5 show 1,3, and 4 LEDs on continously never
> changing. The bottom 
> 6 thru 10 change as I hit the keys as if it is
> responding however LED 
> 7 never comes on. Can someone offer advice. I have 4
> CEM3310s out on 
> the top voice board. It is to my understanding I may
> get a noise out 
> if configured right to see functionality before I
> buy expensive chips.
> 
> Sorry long but I am very happy to be at this status.
> Can sequencer 
> shut down operation. Was curious, should I get sound
> without 
> sequencer.
> 
> 
> 
> --- In vintagesynthrepair@yahoogroups.com, "Frank
> Simon" 
> <fsimon001@...> wrote:
> >
> > I did find a chip pulling down DB4 on U311 it is a
> 6514 4K CMOS 
> RAM. Thank god for IC sockets. The only problem I'm
> a little confused 
> on a cross for it. It appears obsolete. It is called
> D444C on the 
> chip and 6514 on schematic. Can anyone offer advice
> on a cross.
> >   ----- Original Message ----- 
> >   From: fsimon100 
> >   To: vintagesynthrepair@yahoogroups.com 
> >   Sent: Friday, May 30, 2008 8:58 AM
> >   Subject: [vintagesynthrepair] Prophet 10 dead
> > 
> > 
> >   Was curiouse if anyone can offer help. I bought
> a dead P10 no 
> lights 
> >   or anything. The processor is good. I put logic
> analyzer on 
> decoder 
> >   output and see ROM1 (Y0) and RAM (Y5)(which I
> believe is the 
> scratch 
> >   pad memory)active at start up. All address buses
> and Data buses 
> are 
> >   active. I am not certain the algorithm. A flow
> chart would be 
> nice or 
> >   some help with what I should see at some
> critical points. I am 
> >   wondering if there is a chance the ROMs lost
> programming and how 
> would 
> >   I know. Even if they did shouldn't lights and/or
> display come on. 
> And 
> >   yes the power supplies are good.
> >
> 
> 
>