My crate guitar amp cuts out at random times and gets quieter, until no sound comes out. But if i hit it on top, it will return to normal volume.

Stef, January 2009

sounds like a dry solder joint you will have to either get an amp repair man or electronic engineer to sort this out if your amp is out of warranty

byron, April 2009

Stop hitting it! You'll only worsen the existing problem, which is probably a 'dry joint'. Is it still in warranty?
If not, take it to someone who knows what they're doing. Ask local musos to recommend an amp tech.
Look after your gear and IT will look after U, an' that!
Failing that, buy a big lump hammer for a pal and get him/her to thwack it on demand when it plays up.
The choice is yours . . .

Thewlis, January 2009