I can't believe I finally have one of these! I've wanted one for a very long time! It's dirty on the outside, the pots were scratchy as heck, and it was making some odd noises and cutting out then sounding awesome, then cutting out again... I cleaned all the pots, jacks and sockets and replaced the preamp tubes and it sounds awesome!
I'm going to replace the 39 year old electrolytics and B+ dropping resistors for the sake of reliability. I may leave the ancient GE 6550 power tubes in it and just check the bias. It's tempting to change it over to EL34s for a more authentic Marshall sound, but I've heard arguments that the 6550s sound better at lower volume levels and might actually be better for the type of blues rock that I play on an amp like this.
I'm trying to figure out if the ribbed plate made in Japan ECC83s that were in it were original to the amp.
They haven't made regular production Marshalls like this in a long time- since about 1984!
39 year old electrolytics! Scary!