Recently I looked into my amp to see if it needed new caps (Turns out it had been recapped by the previous owner). While I was in there I decided to see if I could bias it, because I'm sure the guy who sold it to me just threw in these Ruby Tubes from the back of his closet before he sold it to me. Anyways, I was trying to follow the guide at the top of the forum that suggested measuring across the 3.8 OHM resistor to get 25mV, but I could only find one 3.9 OHM resistor and across it I get a constant 520mV reading, regardless of what position the trim pot is in. Is it possible I'm doing something wrong?? Maybe reading across the wrong resistor? I followed this guide (http://www.regiscoyne.com/tech/bias/) and biased the tubes to around 14 watts, which I figured was a safe spot, but I'd like to know the true way of doing this. Attached is a picture where I circled the resistor I'm measuring across and the trip pot I'm turning. Keep in mind I'm not very proficient at this yet, so if something is wrong please let me know. Thanks for any help in advance!
There should be a separate
There should be a separate board that is the driver board where you measure. Should look something like this: