Prophet-600 needs help, dead knobs

Post by **prinsen** » Sun Jul 20, 2008 3:06 am

The knobs (pots) of my Prophet-600 are not working. None of them do anything.

All switches, keys, and the membrane panel work just fine - and there's sound.

When tilting the panel open, to get to the guts of the P600, parameters may change randomly.

I've made a video (2m30s) to illustrate the problem. Hopefully it'll explain things better than I can here.
http://youtube.com/watch?v=-a59MWBXdsM

I'm guessing it's an easy fix and I'd love to do it myself, but I don't know where to start. All input is appreciated.

Thanks!

atkbg · Post by **atkbg** » Mon Jul 21, 2008 8:55 pm

Some people have moved both pitch and mod wheel up then down. This seems to reset the cpu while scanning the buss (or more so, causes it to be the item scanned).

Chances are, you have a dirty pot that's continuously sending data.
When it locks up, slowly turn each knob, one at a time, until it unlocks.

Post by **prinsen** » Mon Jul 21, 2008 10:16 pm

Thanks.

Tried turning each knob slowly up and down several times. No success though.

Someone on Youtube suspects my Prophet-600 of having a case of cold solder joints. I was hoping I'd be able to do the error detection myself, got a multimeter and all. But as I don't know where to start looking and what values to look for, it looks like the Prophet needs to see the tech.

pricklyrobot · Post by **pricklyrobot** » Mon Jul 21, 2008 11:50 pm

No advice to offer, other than to say that the P-600 is great fun when it's working properly.

I do have PDF's of the User and Technical Manuals that I could e-mail to you if you don't have them and think they might be helpful to you, or your tech if it comes to that.

Post by **prinsen** » Mon Jul 21, 2008 11:54 pm

Thanks, that would be great!

PMed.

Ollie Stench · Post by **Ollie Stench** » Tue May 08, 2012 2:42 am

I have a Prophet 600 with the same problem. After some internet searching I see that this is not an uncommon problem, but nowhere can I find the necessary repair. Anyone out there get this figured out, and if so what is the remedy?

synthparts · Post by **synthparts** » Tue May 08, 2012 2:50 am

Could be a bad DAC chip. I have them if you need one.

Ollie Stench · Post by **Ollie Stench** » Wed May 09, 2012 2:03 am

What are you asking for the chips?

synthparts · Post by **synthparts** » Wed May 09, 2012 7:43 am

The DAC is $60.

themilford · Post by **themilford** » Wed May 09, 2012 4:09 pm

I had a similar issue after replacing a busted switch on mine.... check continuity on the fixed ribbon cable between the two panel boards...

Also, check cold solder joints etc.

upunkt · Post by **upunkt** » Sun May 08, 2022 2:13 pm

I can confirm that slowly moving all pots can help solve the problem. I could not track it down to a single pot, so I moved all of them (two at a time) approximately 70-80 times. After that, all knobs were responsive again.

Prophet-600 needs help, dead knobs

Re: Prophet-600 needs help, dead knobs

Re: Prophet-600 needs help, dead knobs

Re: Prophet-600 needs help, dead knobs

Re: Prophet-600 needs help, dead knobs

Re: Prophet-600 needs help, dead knobs

Re: Prophet-600 needs help, dead knobs