What are the common problems with the SCI Prophet 600?

[Ashe37]

give the juno 106 time, it will.

[HideawayStudio]

I have had mine since 1983. It worked well until 10 years ago - it started acting weird, some of the the knobs stopped working. I took it completely apart, cleaned all switches and pots and it worked perfectly for another 10 years. I let it sit for a year and turned it on...and oh dear - it is a very sick synth Most knobs do not work, the keyboard works fine but only the synth filter section works - non of the amp and filter envelope knobs work, the volume knob doesn't work, or tune knob, glide doesn't work....it's probably easier to say what does work. The filter cutoff works!

So I stripped it down tonight - COMPLETELY and cleaned all pots and switches - no luck. I removed every single chip - cleaned the connectors and reseated them - nothing. Something is major league screwed up. If it's ONE bad pot how on earth would I find that? Put an ohm meter on every one I guess and turn the knob. Could it be the CPU? I will probably ship it off to wine country and see if they can fix it. It was well worth the thousand pounds I paid for it - 34 years of fun - give or take a year!

Compare this to my 1980 Korg MS20, 1981 Roland Juno 106, 1983 Roland SH101 - these are all ancient too and have never had any issues, whatsoever.

The P600 is a pretty well designed synth as were most of Dave Smith's designs. The chances of it being the Z80 CPU are almost zero - they are remarkably reliable. I guarantee unless there has been some sort of horrific battery leakage it won't be anything major (despite it causing major symptoms).

The Juno-106 is not without its issues (not just voice chips.. bad sliders, bad tactile switches, bad keyboard contacts, failing MUX chips, PSU issues etc), the MS-20 isn't without its issues either with many now suffering from leaking EL caps corroding pcb tracks and the SH-101 often has a really silly problem with worn out power switches causing tuning issues of all things!)

[madtheory]

Well d2mrp0 only has anecdotal evidence. We've just heard from HideawayStudio who has worked on more synths, and certainly more rare synths than most synth techs! So which one you gonna believe?

I've a mark 2 MS20 here. It has had the EL caps replaced, but there's a really annoying noise from the HPF cutoff pot. Pot is good, gonna try replacing the nearby decoupling caps. Probably not caused by corroded tracks I'm guessing?