Oh yes. The ticket to hell, or heaven depending on your point of view. This came to me with complaints of noise and poor volume. The owner runs it with only 2 of the 6550 tubes at 50 watts. He was certain it was dead tubes. These are big amps and I can make good dough on a tube sale for them. Caps too...
But the filters were all new and it's a good job too! And the tubes all tested great. Amp was only drawing about 6ma per output tube. So just a good cleaning and re-biasing is all it needed to get going. Also replaced the 100k cathode resistor in the cathode bias tone stack. It had drifted to 130k and this is common. Check that one if you have spits and crackles!
This particular one was modded to behave like a JCM800. Good job too. Nice, creamy and nasty distortion at any volume!
I was a 100 watt Marshall player for years. This is one of the last really attractive ones with the 60's styling. After that they went the way of the cheap looking President Ford/Carter suit. Boxy, ugly and ready for the CBGBs punk Los Angeles heavy metal era. Part of the early Marshall amplifiers appeal is it's beauty. They are some of the best looking amps on the planet. Notice how well it goes with my Persian carpet? Yes. Psychedelic all the way.