[sdiy] Arp Solina with excessive chorus noise

[Oakley Sound]

 > Except in cheap crappy switched-mode power supplies, electrolytics 
just don't fail.

Say what?

I have replaced many many leaking (or leaked) and exploded caps in my 
time. Worst offenders are Korg's of the late 1970s (eg. PS-3XXX series). 
The little beggars are full of 16V caps riding on the 15V rail and they 
almost all leak, eat into the board and go open circuit.

Roland's from very early on, RS-101, RS-202, SH-3 etc, also have many 
leaking caps. The string machines in particular have problems with the 
sustain caps - that's one leaky cap for every note on the synth. These 
guys don't even get hot. Yamaha CS series (the monosynths - I've not 
often played with the big boys) have also poor electrolytics on the 
power decoupling side. Again they go bad and leak. These sometimes go 
short and take the power supply down.

Oddly enough it's the power supply smoothing caps that do seem to last 
better. Even so, after replacing tens of caps elsewhere it's normally no 
bother to replace them too. The Pro One's smoothing caps in the UK are 
often in poor state since they're being over voltaged considerably with 
our 240V supply. They should be replaced by 50V parts or better still 
also replace the (inevitably humming) transformer with a 2x15V toroid.

I have seen some horrendous cap replacement work though. Poor 
desoldering and soldering leaving tracks lifted and through holes 
trashed. As well as using woefully inadequate parts for the smoothing 
caps which should be rated properly for working voltage and ripple current.

Tony

www.oakleysound.com