whats wrong with my Marshall?

[redjrl]

     Alright so ive had this Marshall MG50DFX for about 3-4 years. i got it used and you could tell cause the fan in the back has always made this really annoying buzzing noise. other than the fan this amp has worked well, up until a few days ago when it decided that i had had enough i guess  xP. it just gave out randomly in the middle of me playing a song. the power light still turns on and the stupid fan still buzzes but its not makin music! the only way i can get any sound out of it is if i turn the volume all the way up and hit a really loud note, it will make a really crappy note for about half a second and then its quiet again! Ive played with all the knobs and tried every setting i could and it only makes the short note when everything is turned up. the fuse is still intact and thats about all i know to check. i know it isnt the guitar or cable cause ive tried multiple guitars and multiple cables and its always the same.

[J M Fahey]

The first thing to do is plug a guitar cable from loop out to loop in, did you recover sound?

[Davelectro]

As far as I know, MG amps suffered quite a lot from bad solder joints. Look for one of those especially on the gain/volume pots.