Hi All; I have one channel out on my ST 70. I can't figure it out.
Swapped tubes with known good one; stays in that channel.
Swapped output tubes.
Checked PS all voltages going into the board are good.
The output tubes bias up right to 500 ma on each tube and I get 0 mv by adjusting the balance resistor.
I do have a funny reading on one of the transistors; 28 v on one side of the right transistor; but I only get 18 v on the left transistor. I measured all possible links in the chain and that is one difference; the lower reading is on the bad side. I measured the resistance on the trimpots and they are all the same for each channel so that looks good.
I can get volt readings for the tubes if that would help.
The speaker jacks are good; I get sound out of both channels until the amp warms up; then it dies in one channel. I use the ST 70 transformers.
Thanks for any advice.