marshall mg50dfx

[Timaaahhh]

I own a marshall mg50dfx. I was playing it when all of a sudden the sound crapped out. Check basics like guitar, cable,ect. all ok. the sound comes and goes when i tap on the top of the amp but never actually comes back to normal. I removed the board to check for a loose connection because thats what it seems like it would be. didnt find any but noticed when i wiggle the harness going to what im guessing is a transistor ( the black box in the back right corner ) the sound cuts in and out. any one ever run into this problem?

[Enzo]

ANy chance you can post a photo? Black box sounds more like a transformer than a transistor.

I would explore the solder that connects the wires to the circuit board. Also check solder under all jacks and controls. When you flex the wire harness, it also flexes the board.

I would also suspect dirty jack contacts on the headphones jack and the effects return jack.

[Timaaahhh]

just read about bridging the fx loop on another post, didnt work. mabey it is a transformer, its the only black box in there besides the fan. im new to the wide world of amplifier repair so not really sure of the correct names of things.

[Enzo]

I don't have one to look at at the moment, all I have are the schematics. That is why a photo would be great.