[Boatanchors] NC-188 re-cap query

[Freeberg, Scott (STP)]

Very loud buzz is often due to the high voltage electrolytic capacitors =
being bad or dried out, allowing AC onto the plates of the audio amp.  =
You can use your scope to determine if there is a ton of AC present on =
the plate of the audio amplifier tube.  I am coming to the conclusion =
that if a vintage HV electrolytic cap isn't bad, it is going bad.  This =
is based on my own experience.  I have two radio's down with bad HV =
electrolytics.  Recommendation is to replace the high voltage =
electrolytics first, get rid of the hum, and then decide if you need to =
replace all the caps.  Its a big job to replace all the caps and will =
likely require a re-alignment.  Disc ceramics are usually ok.  I've =
heard that postage stamp mica's can go bad over time.  Haven't had any =
experience with those though.  Just a friend trying to help.

73, Scott WA9WFA