Today, it was my '89 JTM45 reissue. A while back, it started getting a bit wonky and cutting out. I thought I would change the screen resistors and filter caps as they were 36 years old. Since I had a set of new TAD EL34s, I also put those in. When I went to bias it, I couldn't get over 27mA out of the adjustment. I saw that when I first had someone convert it from 5881 to EL34 tubes, a resistor was added between a resistor and cap in in the bias circuit. It didn't look right to me, so I found the correct schematic online and went to Amp Club today to find out. Sure enough, Scott told me to yank it out, and we'll measure from scratch. With that resistor out, it was 22mA.
I just happened to bring with me the resistance decade box along with capacitance decade box and signal generator that I bought from T-Rex when he was selling everything. I wanted to learn what they were used for. We hooked it up and set the bias adjustment at halfway, then started playing with the controls of the decade box. 150K gave us 394 plate volts and 38mA. So, I soldered in the new 150K resistor, and we checked the results which were the same.
I should have taken more photos but things were busy, and I didn't want to prevent Scott from doing his own stuff. This is a great piece of kit, and saved us a ton of time. I'm very happy I bought it.
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