Here's one for you... Guy brings a Pro Reverb type amp in for service, says one 6L6 won't light. Sure enough, with the power on and in standby, there's no light on one power tube. I pull the two 6L6's and sure enough, one the dead one pin 2 to pin 7 is open. Okay... new tube time. Or so I thought. Go to test voltages.... With no power tubes, the PT is putting out about 525VDC... should be about 460-480... but here's the bias tap is -120V, and that's before the 470Ω bias dropping resistor.!! With the power tubes in, the plate voltage drops to 318VDC with like -150V at the bias junction. Should be 440V at the plate and -51V at the bias point. It's a standard 325-0-325 V, 370 VDC @ 200 mA (DC) with 50 V bias tap. My first thought is bad tranny... Thoughts?