[sdiy] SH-101 repair question

[Steve Ridley]

> Even the mythical electrolytic capacitors that are "so old that they're ready to fail".  
> Naturally, there are plenty of anecdotal stories to the effect of "I replaced the capacitor 
> and the LFO started working again!"  Guess what, newbies?  It wasn't the new capacitor that
> fixed that LFO, it was the simple act of soldering another one in!  You would have most 
> likely gotten the same result by simply reflowing solder on the old capacitor.

There's nothing mythical about electrolytic caps going bad.  They can and do.  
Heat is usually the enemy, but not always.  If the equipment runs hot or the 
cap is right next to a heatsink, suspect the worst.  OTOH, I found two dead 
electrolytic caps in a (professional) microphone a couple of weeks ago - and
mics don't run hot.  There was nothing mythical about the unmeasurably high 
ESR or the brown stain underneath the caps.  

Get yourself an ESR meter and decide the truth for yourself.  They will usually 
measure caps IN CIRCUIT!  Brilliant tool.  There are two or three affordable 
models - I like the Dick Smith one.

I agree with the general suggestion that most faults are more mechanical than 
electronic.  Dry joints, faulty pots and connectors, even cracked/broken boards.
However, devices at inputs and outputs can get abused, and faulty, dodgy or 
just plain wrong power supplies get plugged and take out seemingly random parts.

So keep an open mind.

  
Steve