I bought it recently for $20 and I wanted to fix it abit. The thing is I cant open this . I have a picture of the back casing. One of the screws is stripped the other keeps spining and spining but its not coming out. Same with the fuse box. It just spins around and around. Is there anyway to remove it?

I can't quite make much out in your picture, but I'm on a phone with a small screen so im sure its partly my fault.

Most amps have their chassis attached through the top of the cab, four screws or so and it falls out. Granted I'm not familiar with valvestates, spose it's a possibility they do something weird and cheap.

I know their was some weird tool you could use to drill into a stripped screw, then they gave you a special bit with it that grabbed and undid the screw. The one that's just spinning can probably get taken out with some gentle fenagling with pliers.

If you can't see the preamp tube I'm sure you could google how to replace it or just contact marshall on how to get the chassis out.
*insert witty statement here*