Awesome thanks for the reply!
I received confirmation from Boogie support as well that it was a 39 ohm too.
Here's the saga...
- removed PCB (yup, just as fun as everyone says it is)
- cleaned charred sections of PCB, rerouted vaporized PCB traces and cleaned off cap goo from leaky caps
- replaced burnt resistors and replaced all electrolytics
- rebuilt Vactrol (LDR was fine so I extracted the dead LED and replaced with a 3mm red LED) Works perfect!
- new set of matched output tubes
Everything is back together and works! Even the footswitch!
But... two minor issues:
1. EQ LED on dim when disabled - EQ works fine but the LED stays on very dimly when switched off. Makes no difference if footswitch is plugged in or not and symptom is the same on the footswitch LED.
I suspect there's a trace on the PCB that has just enough potential to ground to cause this. But where?!
2. 60 Hz hum - for a bit
When the amp is cold there's a noticeable 60 Hz hum. Not too loud but does go away after the amp warms up for about 5 min. Gain and output controls do not change its level. All quiet at the record out so the preamp and EQ section seem good.
I traced it down to the output driver section. If I remove the driver tube speaker output is silent. Tried replacing tube and made no difference.
Also noted that adjusting the presence on the the active channel gets rid of the hum. My guess is because the output is being fed back in to the driver tube 180 degrees out of phase.
Once warmed up the amp has a faint 60 Hz hum but only noticeable in a very quiet room. I consider this acceptable.
I tried cold spray on driver area components but it had no effect.
At this point I think it may be something to do with the PCB itself (internal damage? Moisture/age?!) and may be only solvable by replacement.
Throwing it out there to see if anyone has any ideas.
Cheers!
