I recently acquired an R85 that I am cleaning up. I have replaced the needle, belt and optical sensor. Whenever it is not playing a record there is a VERY loud hum that goes away as soon as the needle touches a record(then it sounds great) There is a light indicating Left Channel overload in the amplifier lit. Is this a bad transistor? Any way to test? It even hums when the power switch is turned off (though not as loud) requiring me to unplug it.