Vintage Synth Repair

Having repaired around 300 Prophet 5s, I'll just say that the tantalum 
bypass caps (used on the power supply, CPU and voice boards) are the 
leading cause of failure in this synth.  The first thing I always do is 
replace them with equal value high-temp electrolytics -- have been doing 
this for years with no problem.

~GMM


>
>     -----Original Message-----
>     From: Susie
>     Sent: Sep 30, 2010 7:23 AM
>     To: vintagesynthrepair@yahoogroups.com
>     Subject: [vintagesynthrepair] Re: Turning a vintage synth on after
>     30 years
>
>      
>
>     The electrolytic capacitors in the PSU (amongst others) are likely
>     to be dried out, and as you are going to have to replace them
>     anyway that's the first thing I'd do before powering on.
>
>     I've seen other advice about using a variac to slowly bring the
>     voltage up over a period of hours to allow the caps to reform, but
>     I don't think caps ever reform to their previous new state.
>
>     I cheap tip I picked up from repairing old valve/tube gear is to
>     do the first power up with a 100W incandescent lightbulb wired in
>     series with the mains supply - you can knock a socket and plug
>     arrangement up really cheaply, possibly with bits you already
>     have. The lightbulb acts like a current limiter and even if
>     there's a direct short somewhere, the unit can't draw more current
>     than would naturally flow through the bulb ~ 0.4A here in the UK.
>     I'm not sure if that's really necessary with 'modern' (30 years
>     old) gear though, but it gave me a bit of extra confidence with
>     the 1950s Jennings Univox I brought back to life. If the lightbulb
>     glows brightly then there's something very wrong, but you
>     hopefully haven't done any damage. If it's healthy though, as was
>     the case with the Univox, the lightbulb won't light, although of
>     course it doesn't follow that an unlit lightbulb means you have a
>     healthy synth - it's all about confidence levels.
>
>     Cheers
>     Susie
>     http://www.myspace.com/susangardener
>
>     --- In vintagesynthrepair@yahoogroups.com
>     <mailto:vintagesynthrepair%40yahoogroups.com>, "stompboxaron"
>     <mylists@...> wrote:
>     >
>     > Any tips on how to minimize any damage when turning on a vintage
>     synth after 25+ years? One is a Prophet 5 and the other an
>     Emulator II.
>     >
>     > Just trying to get any ideas other than just plug it in and go
>     for it.
>     >
>     > Thanks!
>     >
>     > Aron
>     >
>
>