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Had a Marshall MG50CFX which had a high pitched squeal coming out of the speaker when you first powered it up...then after about 30 seconds or so, it went away......this occurred with all controls turned down and only the master volume turned up...turning the master down also turned this noise down as well....It reminded me of the squealing you get when caps go in smps... The problem was with two caps in the power supply....10uf/50V.....these checked ok but I had some there so I decided to take people's advice here and just replace them if I suspected them...hitting them with a shot of cold spray would make the squealing stop if you did it right away....if you waited too long then the squealing would go away on it's own...Tried a heat gun but did not get the original caps to act up... I guess when these caps were at room temperature they would act weird but above or below that they were fine...so I swapped them out anyway, tested it,turned it off and let it sit for an hour, tested it again, let it sit for an hour again and it tested ok. So I guess the moral of this story is if you suspect a component to be bad,especially inexpensive components, the best test is substitution.....Thanks to everybody who kept saying this to me...I finally listened...
Cheers,
Bernie
Cheers,
Bernie
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