Vintage Synth Repair

----- Original Message -----

From: fsimon100

To: vintagesynthrepair@yahoogroups.com

Sent: Saturday, June 07, 2008 11:42 PM

Subject: [vintagesynthrepair] Re: Prophet 10 dead

The control panel (micro computer system)is working. I am planning to
set the ADSR soon. Right now I verified EQ board is good by injecting
audio generator. I attached a schematic section to discuss a bug with
the sequencer. Once I resolve this I should have a CEM3310 issue and
I may have a P10. If anyone has a P10 schematic or wants to look at
my attachment, I wanted to ask help with something. If I ground pin 1
on the 4556B decoder the sequencer panel lights up and I hear the
tape deck come alive. So I am not getting a logic Low out the gate
feeding the decoder enable. This schematic is not like my Sequncer
board schematic but basically my -IOREQ output from Z80 needs to go
Low but is not. Not sure if this is still a hardware problem (which I
see how) or a firmware issue EPROM.

I attached a schematic page in the Files section called P10 Sequencer

--- In vintagesynthrepair@yahoogroups.com, Stephen Jones
...> wrote:
>
> I would have to go look at the schematic, but from
> memory I think that it would work.
>
>
>; --- Frank Simon ..> wrote:
>
> >; Thanks. Shouldn't I be able to Inject an audio
> > generator on the coax connecting the voice board to
> > the EQ board to prove the EQ board functional.
> > ----- Original Message -----
> > From: Stephen Jones
> > To: vintagesynthrepair@yahoogroups.com
> > Sent: Friday, June 06, 2008 5:56 AM
> > Subject: Re: [vintagesynthrepair] Re: Prophet 10
> > dead
> >
> >
> > 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 ..> 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"
> > > 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.
> > > >
> > >
> > >
> > >
> >
> >
> >
> >
>