I know four personally and two of them very well. But I don't think they'll go on a gun forum.
I'd be glad to pass a question on to them and one of them would possibly even call you if I asked her nicely.
(But I wouldn't blame you if you didn't want to go that route).
If its the Marshall type...what you wanna know? I use to service guitar tube amps before i became a federal technician (no time). I still have a nice stash of tubes, parts and all my schematics and test gear.
I build my own amps. My main halfstack is a JMP 100 built off a 1970 original Marshall schematic and I added a Master Volume and tweaked the preamp a lil. Its running (4) EL34's. I have a 50w "marshall" that i am building its going to be a JCM800 version but with a custom built PTP board that i made (i use to make the boards custom too) and it will run 6550's.
Not sure if it's a speech thing, but Indiana has great programs for that sponsored through the state. Sliding income based payments as well. My insurance covered most of the cost actually.