[sdiy] unstable behaviour

[phillip m gallo]

Sometimes, instability that "sounds" like cabling intermittency is has
other causes.   These causes can be an instability caused by extending
input circuits without shielding causing oscillation.   This oscillation
can be as likely low frequency as high frequency and may be the direct
cause or the indirect cause.  When indirect, it could be a super-or
infra-sonic oscillation that periodically saturate a circuit or modulate
the audio passing thru the circuit. 

Sometime even shielding a wire (and any resulting "flexing") can be the
cause if the ground is poor one.   It sounds as if you've done a good
cosmetic inspection (with a refreshing humility) so you might want to
hook up the o'scope (storage helps here) and catch some of these
"aberrant" events.   Often the wave shape can tell you the nature of the
problem.

regards,
p