That doesn't mean it could not have high ESR, but it was definitely not the
cause of the problem. There are people who like to change ALL the caps in old
hifi amps, I think they're wrong. While I will agree with changing the
corresponding cap in the other channel when you find a bad one, or even weak
one (significant ESR compared to Xc) it does no good to just change them all
arbitrarily.

Sure it does. If the problem is with one of these caps, changing them
arbitrarily FIXES the problem.

€œPenny wise, pound foolish.€� Yes, youre right, finding the ONE cap
that is the cause is technically proficient. But just to say €œI found the
culprit!€� does not help the customer (or yourself, if its you). The unit
will be back on your bench very soon if you dont replace all electros now,
if you find one or more below spec.