So I have this HB. Been playing for years w/o problems. Now when I built it I noticed one transistor hogging current and tried changing outputs of the 3 pairs to try and get a even match. I have done that multiple times and it always shows back up on the same transistor. i have changed enough even today (2 of 3) and it still persists. In pic I'm measuring the output of the one affected. It is running at 42mA vs. 14 and 17 of the other 2 in group. The emitter resistor measure equivalent on all 3 (.22 ohm) and the base resistors all match at 2.2 ohms. What are the next steps? Check the mica insulator? Replace mica? I have the exact same setup as far as physical layout on heatsink on the other channel with no problems. Understand it will play and sound great in this condition for very long period of time. Just would like to fix while in it.
Got it. On closer inspection tapped hole for tranny mount was not flat. Countersunk and used existing Mica, remounted and measures good now @15, 16 and 14.5 mV on emitter resistors.