by EWBrown » Tue Feb 03, 2009 10:19 am
It appear that two tubes are operating, and drawing plate current and that two are not.
A little bit of hum is normal if you do not have the input connectors shorted or loaded to ground.
For the two (left channel) that give no reading, the first step would be to to check the plate voltage on pin 7 of each of those two tubes. If there is no voltage present, then go back to the terminal strip or connection for tha centre tap of the output transformer where it connects to B+. It appears there is a possibility that there is an open or not complete connection.
Also make sure that those two tubes have lit filaments, as cold tubes also do not conduct or draw plate current.
HTH
/ed B
Real Radios Glow in the Dark