DSI / Prophet Forum

coolscott7 · Joined: 26 Jul 2007 Posts: 1 Location: Minneapolis

Hi
I just bought a prophet 600 on ebay. Some of the keys will not produce
sound. But its not always the same keys. The location of the silent
keys varies. Does this mean one or more of my voice chips are out? Ive
had the same problem on one of my prophet 5s, but its very intermittant
and usually clears up. Any ideas? thanks! Idea

sjones · Joined: 19 Apr 2007 Posts: 233

Yes, it sounds like you could have a dead voice. Its probably not a VCO, since you it sounds like you have a completely dead voice, but more than likely a VCF or VCA.

What I would do is turn off OSC A and B and set resonance to 10 and contour to 4 (so the filter is oscillating), press tune and then play a 6 note scale. If you hear a sound on all 6 notes, then you have good filters and amps .. which would mean you'd have two dead VCOs (potentially, or bad components around them). If you hear silence on one of those 6 notes, then you've either got a dead VCA or a dead VCF.

torinkrell · Joined: 06 Apr 2009 Posts: 38 Location: NY-NJ USA

Sjones has given excellent advice. However when playing those six notes do make sure to play a chromatic scale so each of the P6's voices has a chance to respond sequentially. Otherwise it will take more than six notes to go through all the voices as at least one voice will be skipped whenever any non-adjacent keys are played up (or down) a musical scale.