[sdiy] Roland JX-3p vca - noise

[Oakley Sound]

 > do you have any idea how or why these transistors fail?

Old age?

But mute transistors are not your normal NPN transistors because they 
will have their collector voltage taken below their grounded emitter 
every half cycle.

As they age they get leaky and the distortion increases.

Failures of this type are very common in old hi-fi separates like CD 
players and tuners too.

Tony

http://takla-makan.bandcamp.com/
http://www.oakleysound.com