70s Marshall 50w - What Is Going On Here?

[kurtsstuff2003]

It does sound good. I wouldn’t worry about anything once you bias it.
Kurt….. remember that “STOCK” 2204 I sold you years ago and you opened it up and every cap in there was an orange drop? Jesus…. What an idiot I am ………

lol!!

 

[fusedbrain]

Amp sounds decent in the video.
If it will only go to 23ma with EL34's, then it will likely bias 6550's properly.
I'd try that first, and see what you think with the amp properly biased.
Those boards are a bitch to work on, and the traces are really fragile. If you are thinking about swapping out parts, you better know what your doing with an iron, or you are gonna have a mess on your hands.
If you swap in the 6550's and are happy to stop there and just play it, I would recommend lowering the bias feed resistors to 150K for long term reliability.
But..... do not attempt to swap out the 220k's that are on the board now. I would suggest CAREFULLY adding 470k resistors in parallel with the 220ks from the top of the board to get the 150k resistance.

 

[Devin]

Sounds awesome to me! I'd leave it just the way it is