Quote:
Originally Posted by Kevin Kuehn
we're about to the point in time that we need to start shotgunning all mica caps.
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Micas can go bad and I have replaced my share of them, but many more in sweep circuits (horizontal, vertical) and HV circuits. Audio circuits tend to be more forgiving, but if you find a bad one -- or two -- there, of course it has to go.
I would not advocate shotgunning micas in IF stages unless you are well equipped and well versed in alignment, since a slight change in lead dress may kick things out of whack. Ditto, even more so, for the tuner section. Service manuals often included warnings to keep your clumsy mitts out of the tuner.
These days I look on mica caps as I do resistors. Generally more reliable than the hopeless paper caps, but not immortal. If a basic (paper + electrolytic) recap doesn't magically fix everything, then the next phase is to look at micas + resistors. One thing that I do during the basic recapping phase is test every component on the same terminal where I am connecting a new cap, the theory being that if I'm disturbing (unsoldering & resoldering) anything on that terminal, I may as well deal with everything at once to avoid trashing the connection with repeated monkey-wrenching. That way, I naturally uncover some other bad parts as I go, although it's not very systematic.
Phil Nelson