DSI / Prophet Forum

[Nigel99]

Hello all,

This is my first post. I have inherited a D.O.A Rev 2 in seemingly good cosmetic shape inside and out. The previous owner–a close friend of mine told me that the synth worked well until it needed a power supply rail repaired. After that it worked for a while and then eventually went down again and was put into storage.

I have had a tech working on it for over a year now, on and off, and I am wondering if any of you have experienced this problem:

"The machine will not boot with any voice board connected. Boots fine with no voice board connected. Most likely an issue with the autotune, PSU went high when it failed."

Any leads you may have would be greatly appreciated.

Nigel

[dougt]

Check the voice board for shorted tantalum caps. Very common problem with these.

Doug
synthparts.com

[Nigel99]

Doug,

i'm fairly sure they were the first things to be replaced. I think that the root of the problem is damage from a faulty PSU that was not fully repaired the first time it went down years ago.

When functioning boards are connected we still have the same problem. The machine will not boot. Disconnect the boards and the computer will boot, switches operate.

[rikusk]

This is autotune problem for sure.

If you have oscilloscope, probe the saw output test points on voice board. All the waweforms should be in same range, at least in audio frequency. If there is voice missing of the frequency is low, the tuning will take for ages, because cpu counts the cycles of the output of each oscillator.

In case if you have proper output on all VCOs then check tuning multiplexers. Does the multiplexed signal go through to the counter on CPU board.

[Nigel99]

Thanks for the tip–I will get my tech to check it out when he gets a chance and post the results here.

It was also his suspicion that it was an autotune issue but he has been over the circuit and everything seemed fine.

Nigel

[rokuez]

i just got my prophet 5 rev 2 fixed by greg over at http://analogsynthservice.com/



i had my prophet 5 unplayable with no pots working to change parameters except cutoff, and none of the voices playing properly; for a year I was mulling over whether or not I could repair it. I was worried about frying ssm chips

so I drove my p5 up to greg and he repaired it quickly for a very reasonable price.






If you send your prophet to greg I cannot stress putting it in a road case at the least before you ship it and insuring it for the maximum amount that you can.


i heard at tonetweakers.com the recommend wrapping a synthesizer six times in one inch bubble wrap.


if you have to ship it pack it with as much padding as possible.