This restoration was a bit tricky. Initially, the symptoms were loud humming and distorted sound which usually means old capacitors. After replacing all capacitors, the humming was gone but the distortion issues continued. Next tubes were tested and replaced as needed. Still, after the unit warmed up only a very low volume was achievable and anything above that was completely distorted.
Finally with some encouragement to keep at it, it was traced to an open-circuit resistor on the emitter bias for the pre-amp before the final amplifier stage. Now, this unit is just like new complete with new needles and rejuvenated mechanicals on the turntable. Amazing how nice 1940’s technology can sound – rich bass!
Prior to replacing components, someone had already been at one of the capacitors:
Finally, a new set of tubes, capacitors and a new resistor as well:
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