Vintage Synth Repair

Not being funny but I think we said this like 3 weeks
ago....I repeated it too a few days ago.

He has a problem in the digital domain that's plain to
see....but from the kind of things he's said he needs
to read some books on that kind of stuff, do a bit of
research etc otherwise it's stabbing in the dark time.

Ok carry on I'll shut up now :) 



--- thirteentech <thirteentech@...> wrote:

> Yes, it sounds like your computer is not running,
> and you are getting random LED's when 
> you power up. Do you have an oscilloscope and any
> experience troubleshooting 
> microprocessors? If not, you will need someone who
> can I think.
> 
> --- In vintagesynthrepair@yahoogroups.com,
> "fsimon100" <fsimon001@...> wrote:
> >
> > Steve,
> > I down loaded  a P5 service manual. It is very
> helpful and much 
> > better print than the P10 schematic I have. I can
> now see the what 
> > you meant by the subtractive synthesis gated by
> the CEM3310. I just 
> > need to isolate why the control panel is dead. I
> have two LEDs light 
> > up when I power up but not everytime I power up. I
> know the CPU is 
> > good now. I'm thinking it has to be on the
> computer system and not 
> > the Analog or synth section. Would you agree.
> Thanks for your help 
> > and patience
> > 
> > 
> > --- In vintagesynthrepair@yahoogroups.com,
> "thirteentech" 
> > <thirteentech@> wrote:
> > >
> > > Well, I can't guarantee that the machine will
> run OK without the 
> > sequencer, but it probably will, and is 
> > > worth a try. I see one P10 for every dozen P5's
> that I service, so 
> > unfortunately I don't have a P10 in the 
> > > shop to look at directly. 
> > > 
> > > As for service manuals, Sequential put out a
> large folder called 
> > the "Prophet Synthesizer and 
> > > Polyphonic Sequencer System Technical Manual"
> which has the 
> > Prophet 5 REV 3.0, 3.1 and 3.2 service, 
> > > programming guide and schematics, the Prophet 10
> theory, 
> > schematics and parts list, and the Poly 
> > > Sequencer theory and schematics, the Prophet 5
> remote service and 
> > schematics, and update mod info 
> > > for the Rev 3.3 update. much of the P10 section
> refers to the P5 
> > schematics.
> > > 
> > > The basic differences between a P10 and a Rev
> 3.x P5 are: The 
> > P10's master tune is digitized whereas 
> > > the P5's is connected directly to the common
> analog circuit. The 
> > P10 also has 6k of PROM compared to 
> > > the P5's 2k to allow it to scan the keys and
> controls better to 
> > keep scanning delays down to a 
> > > maximum of 11ms. 
> > > 
> > > So if the machine is frozen, the best thing to
> do is to just start 
> > making sure that every CPU line looks 
> > > like it is doing the right thing, and then move
> on to each device 
> > on the data bus and see if it's chip 
> > > select input is working. If it is and you have
> gone through all of 
> > the basic troubleshooting that you 
> > > would expect to do with a microprocessor
> circuit, and it all seems 
> > to be running, then take a look a 
> > > the autotune circuitry, although this is
> unlikely as your TUNE led 
> > is not coming on.
> > > 
> > > 
> > > --- In vintagesynthrepair@yahoogroups.com,
> "fsimon100" 
> > <fsimon001@> wrote:
> > > >
> > > > Steve,
> > > > Thanks. Are these diagnostics tribal knowledge
> or are they 
> > > > documented in a manual. I do not hve the P10
> manual. If I find 
> > one 
> > > > will it give me diags. 
> > > > 
> > > > I have disconnected the Seq board so obviously
> your saying it 
> > will 
> > > > run without it. Great. One system removed. I
> do have a z80 CPU 
> > to 
> > > > swap out. 
> > > > 
> > > > I was thinking the record switch was a
> microswitch so to enable 
> > > > would be a pull down or pull up Res on PCB.
> > > > 
> > > > --- In vintagesynthrepair@yahoogroups.com,
> "thirteentech" 
> > > > <thirteentech@> wrote:
> > > > >
> > > > > I am not certain what the P10's last OS
> revision was, the 
> > highest 
> > > > that I have seen on a 
> > > > > Prophet 5 is V9.3. Looking at the schematics
> of the 2 machines 
> > the 
> > > > CPU board is similar, 
> > > > > they do have different EPROM and NV RAM
> chips. Also the P 10 
> > has 
> > > > different scanning 
> > > > > circuitry because it would have an
> unacceptable scan delay 
> > with 2 
> > > > keyboards as opposed 
> > > > > to the P5's 1 keyboard, which has a maximum
> delay of 10 Ms. 
> > The 
> > > > scanner also scans all of 
> > > > > the buttons during each cycle.
> > > > > 
> > > > > For what it's worth (not knowing if it also
> applies to the P-
> > 10), 
> > > > to enter the CPU and RAM 
> > > > > test on a late rev. Prophet 5, turn off the
> power, put the 
> > record 
> > > > switch to "enabled", and 
> > > > > jumper test point 304 (MEM TEST) to plus 5V,
> then turn on. The 
> > > > machine starts 
> > > > > sequentially flashing it's LED's, to then
> enter the memory 
> > test, 
> > > > press TUNE. It runs through 
> > > > > 4 tests, counting 1-4 as it does them, and
> finishes on 0, 
> > > > indication no failures. If it stops 
> > > > > on 1-4, it is indication a failure of either
> the scratchpad 
> > RAM, 
> > > > NV RAM, PROM or 8253 
> > > > > timer (1,2,3 and 4).
> > > > > 
> > > > > I haven't used these tests on a P10, so I
> don't know if they 
> > > > apply, but otherwise maybe the 
> > > > > best idea would be to disconnect the
> sequencer board and just 
> > > > start the usual traditional 
> > > > > checking of the main CPU lines to see if any
> of the data or 
> > > > address lines are hung.
> > > > > 
> > > > > 
> > > > > --- In vintagesynthrepair@yahoogroups.com,
> "Frank Simon" 
> > > > <fsimon001@> wrote:
> > > > > >
> > > > > > On Brd 3 there are three EPROMs with the
> Z80 CPU. The first 
> > > > says: 0 TEN 5.0, second 
> > > > > says: 1 TEN 5.0, third says: 2 TEN 5.0 on
> their stickers. 
> > > > > > 
> > > > > > On Brd 9 there is one EPROM with the Z80
> CPU. The sticker on 
> > it 
> > > > is not too legible what I 
> > > > > do see is: SEQ (that part is clear) below it
> say C1 or C.1 or 
> > I 
> > > > was thinking maybe 2.1( if 
> > > > > upper half of 2 was missing). 
> > > > > > 
> > > > > > Both Z80s on pin 6 CLK have 2.5MHz clock
> at about 4v p-p. 
> > and 5v 
> > > > dc on pin 11. Does 
> > > > > the EPROM lose all programming if battery
> dies? If so how do 
> > you 
> > > > reload? Will keyboard 
> > > > > not boot without EPROM program. My friend
> today is bringing me 
> > a 
> > > > Z80 CPU in so I can 
> 
=== message truncated ===



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