Vintage Synth Repair

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" <fsimon001@...> 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" <fsimon001@> 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" 
>   > <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" 
>   > <fsimon001@> wrote:
>   > > >
>   > > > 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 <fsimon001@> 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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>   > >
>   >
>