Bought new in '70's. Used intermittently. Right side meter spikes to full volume crackle. Relay contacts, in clear box, flick on and off. All was working great, most of the time, occasionally having loud spike episodes. Now it noise spikes off and on constantly with right side meter. Transformer never seems to get warm. Had trouble with sticking on button. Took it apart and resurfaced contacts. Meter light doesn't work and is black. Amp is clean inside and out. Never been serviced. I have a ohm meter and a soldering iron. Willing to do something if I knew what. Can anybody advise me?
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