Vintage Synth Repair

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

From: thirteentech

To: vintagesynthrepair@yahoogroups.com

Sent: Monday, April 21, 2008 12:21 AM

Subject: [vintagesynthrepair] Re: Prophet 10 repair (was Hi from a new member).

When you turn the machine on the front panel should be dark with the exception of the
[TUNE] switch. The machine boots into it's autotune mode and suppresses all of the front
panel lights and controls while it does so. it should take 8-10 seconds if the machine is
functional, longer if voices are way out of calibration.

Does the TUNE button LED come on when you power up?

--- In vintagesynthrepair@yahoogroups.com, "Frank Simon" ..> wrote:
>
> Steve,
> I have all power supplies in order. There is power to all boards. When I turn it on
shouldn't it boot up and LED's cycle on or blink or even be switchable? The panel is dead.
Does this sound like processor to you?
>
> ----- Original Message -----
> From: thirteentech
> To: vintagesynthrepair@yahoogroups.com
> Sent: Saturday, April 19, 2008 1:07 AM
> Subject: [vintagesynthrepair] Re: Prophet 10 repair (was Hi from a new member).
>
>
> Each of the 5 voices on each voice board has two CEM3310 envelope generators. One
> controls the volume envelope of the voice, and the other controls the filter cutoff of
the
> voice if you bring up the filter envelope modulation control. If the 3310's in the filter
> control line are faulty it should only manifest when you turn on the filter envelope
> modulation. If this is off then the voice should sound if the VCF cutoff pot is set open.
If
> you have bad 3310's in the VCA envelpoe position, the voice won't sound.
>
> I am assuming that your P10 has Rev 3.x Prophet 5 voice boards in it, because in the
> Sequential System Technical manual which covers all Prophets from Rev 3.0-3.2, the
> Prophet 10 and the Poly Sequencer, they all use the same basic voice board. So for
> instance, in Voice 1 of the voice board, U412 is the amplifier envelope generator, and
> U417 is the filter envelope generator.
>
> --- In vintagesynthrepair@yahoogroups.com, "Frank Simon" wrote:
> >
> > Steve,
> > I am pleased to know there is a technique to troube this with the bad ICs. I hope to
get
> to that point soon. If I remember there were no LEDs on control panel lit when turned
on.
> Is there a local spot that isolates that symptom? I haven't removed the top boards yet.
> Hopefully I can handle that.
> >
> > I guess I am confused on VCA and VCF envelope positions. Can you give me a
> explanation of how to determine which state the IC is in.
> > Frank
> >
> >
> >
> >
> > ----- Original Message -----
> > From: thirteentech
> > To: vintagesynthrepair@yahoogroups.com
> > Sent: Friday, April 18, 2008 6:04 PM
> > Subject: [vintagesynthrepair] Prophet 10 repair (was Hi from a new member).
> >
> >
> > Well, if you have metered all of the power supply rails in the machine, and are
satisfied
> >; that they are all in spec, then go ahead and put the voice boards back in. Remove the
> > known bad 3310's, and if any were in VCA ENVELOPE positions, replace them with
> 3310's
> > from VCF ENVELOPE positions. This will allow you to set up a patch with the VCF
> envelopes
> > control turned off and still have all of the voices audible so that you can hear is all
the
> > voices are working.
> >
> > The EQ board on P10's was another source of problems too of you don't get any
> sound.
> >
> > As for the sequencer board, the best way to test functionality is to get the rest of the
> > machine basically playing and then just try out the sequencer and see if it loads and
> plays
> > back notes.
> >
> > Sounds like your power supply lines are the most important issue, so as I mentioned,
> put
> > all your attention on them being correct first. There are lots of CEM3310's in the
> machine,
> > so you can definately get the machine playing without 4 of them, just make sure that
> there
> > are good chips in the VCA envelope positions.
> >
> > Steve.
> >
> > --- In vintagesynthrepair@yahoogroups.com, "fsimon100" wrote:
> > >
> > > Steve,
> > > Thanks, obviously I have a Rev 1. My schematic is a scanned copy and
> > > didn't see the note and still don't but I know you are correct. What
> > > do you think I could have damaged with the 12v I put in? Like I said
> > > U931 shorted and got hot. I know that may be a tough question
> > > without personally probing but the board is holding the 5v now. How
> > > could I verify functionality of PCB9.
> > >
> >; > Also if I put one of the voice boards in with 4 CEM3310 missing can
> > > I continue troubleshooting? Is there a chance I could get confidence
> > > from a oscope or panel lights before I buy four CEMs.
> > >
> > > --- In vintagesynthrepair@yahoogroups.com, "thirteentech"
> > > > wrote:
> > > >
> > > > The Prophet 10 service manual shows that U603 is a +5V for rev. 1
> > > machines, or +12V for Rev. 0 machines. It looks like that supply is
> > > for either a 5V
> > > > cassette drive or a 12V wafer drive depending on which version of
> > > machine you have, but the schematic also shows a note on the 5.6V
> > > rail of the PSU
> > > > saying: "To PCB 9, Rev 0, not used for Rev 1". So depending on
> > > whether you have a Rev 0 or Rev 1, there will be different supplies
> > > on P603 pins 2 and
> > > > 3.
> > > >
> > > >
> > > > --- In vintagesynthrepair@yahoogroups.com, "Frank Simon"
> > > > > > > >
> > > > > Hi Steve,
> > > > > I have a manual I downloaded from paintingwithsound.com. It is
> > > hard to read. I was a little disappointed when the power supply in
> > > my schematic
> > > > states VR603 was 12v T0-3 down to the wire color. Later to find
> > > out as I traced it to the PCB9 Polyphonic sequencer CPU board it
> > > needed to be a 5V.
> > > > It took out a Dual Flip Flop U931. After that I put a proper 5V in
> > > and nothing is shorted. But doesn't mean something else was't
> > > damaged on that
> > > > board just not shorted. That same part was originally bad when the
> > > original 5V Reg was in then the 12V took it out again. That was the
> > > first
> > > > bonehead move. And as you may read from my first mail the CEM3310
> > > story. So my progress is negative. If you can offer a systematic
> > > approach to
> > > > trouble shoot this maybe by isolating boards or whatever I would
> > > appreciate it. If you have a readable schematic you can share it
> > > would be great.
> > > > > ----- Original Message -----
> > > > > From: Stephen Jones
> >; > > > To: vintagesynthrepair@yahoogroups.com
> > > > > Sent: Tuesday, April 15, 2008 9:35 PM
> > > > > Subject: Re: [vintagesynthrepair] Hi from a new member.
>; > > > >
> > > > >
> > > > > Wow, that's a lot of questions. I can help out, but
> > > > > not all at once, I have a workshop full of synths at
> > > > > the moment that I am fixing 1 by 1. Starting the the
> > > > > Prophet 10, do you have a service manual for it?
> > > > >
> > > > > --- Frank Simon wrote:
> > > > >
> > > > > > Hi Steve,
> > > > > > I hope everyone doesn't attack you at once. I had a
> > > > > > crazy experience where I bought a Prophet 10, Korg
> > > > > > Trident Mk II, and Roland JX 10 all for $30 each non
> > > > > > working. I am an RF engineer and novice
> > > > > > musician/Audio repairman. I know linear more than
> > > > > > digital but I am going to throw out some questions
> > > > > > since you offered.
> > > > > > 1)My Trident I fixed due to NiCad battery meltdown
> > > > > > destroying traces but I repaired the PC board(with
> > > > > > wire) and all works great Strings, Brass,
> > > > > > FLANGER!!!, but the Synth section makes occasional
> > > > >; > odd noises sounds like processing. Any trouble
> > > > > > shooting advice would be appreciated.
> > > > > > 2) The P10 had no sound, lit up, I found a 5V
> > > > > > regulator pulled down. Found the bad IC(burned my
> > > > > > finger). Then like a dumb a## I was checking -5V reg
> > > > > > T0-220 on a voice board,slipped shorted output to
> > > > > > input and took out 4 CEM3310. OUCH!! Still don't
> > > > > > know why due to internal Zener in CEM3310. I want to
> > > > > > continue toubleshooting but don't want to buy pricey
> > > > > > chips until my confidence is up. Can I put the board
> > > > > > in without 4 of the 10 CEM3310 and continue. I'm
> > > > > > sure no sound but -5v reg will be up. Any advice
> > > > > > appreciated.
> > > > > > 3) Roland JX10 is total dead. I think power supply
> > > > > > was good. Lower priority. This one I don't have a
> > > > > > schematic. Do you have one?
> > > > > > 4) Finally my Hammond H-112 had low volume and I
> > > > > > found unplugging the Reverb tank it came back full
> > > > > > volume. I think the reverb is ok. Do you think it
> > > > > > could be a tube driver? Sounds odd that it would
> > > > > > shut the amps down.
> > > > > >
> > > > > > Sorry for the overload. I'm excited about these
> > > > > > synths. If I fix one I got more than my money back.
> > > > > > The Korg is very close. I will cry if I can't fix
> > > > > > the P10.
> > > > > > Thanks,
> > > > > > Frank
> > > > > >
> > > > > >
> > > > > > ----- Original Message -----
> > > > > > From: thirteentech
> > > > > >; To: vintagesynthrepair@yahoogroups.com
> > > > > > Sent: Tuesday, April 15, 2008 7:54 AM
> > > > > > Subject: [vintagesynthrepair] Hi from a new
> > > > > > member.
> > > > > >
> > > > > >
> > > > > > Just wanted to introduce myself... I am a
> > > > > > synthesizer service tech from Sydney, Australia. I
> > > > > > have been fixing synths since 1982, as well as a
> > > > > > lot of touring as a keyboard tech. Currently I
> > > > > > have around 22 vintage machines that I play and
> > > > > > use for recording, and have been a warranty
> > > > > > tech in Australia over the years for PPG, Kurzweil
> > > > > > E-mu and Sequential. Hope I can help out a
> > > > > > little on the forum, and learn some new things too
> > > > > > :-)
> > > > > >
> > > > > > Steve Jones.
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > > __________________________________________________________
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> >
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