Why is my amp making this noise?!

sgosden

Ignore the playing. It's the singer on guitar.

Never done it before just started up this practice. 
It's been sat at bedroom levels for about 3 months whilst the band was hiatus (sounds proffesional right? Really drummer broke his shoulder). 

It's a dsl100. 
About a 9 months ago I had some of the resistors and diodes replaced by a tech, as it had overheated and died mid set. 


The new sound is very intermittent,  And goes if I put in on standby or "tap" the head with a fist. ..

Ideas? 

Thanks

Cabicular

Throw it away before it catches fire ...
doesnt sound like a Valve but those amps have a few known issues
make sure you tech it to a tech that has dealt with them
icbm will be along with details I'm sure

ICBM

Probably a faulty preamp valve with some sort of intermittent microphonic problem.

Whatever it is, it sounds hideous even by the standards of a Marshall DSL…

DJH83004

By virtue of the fact that you can bang the head and the noise goes, is actually a good thing as it suggests an intermittent connection (and that could be internal to a valve element as per ICBM's suggestion). Certainly worth taking the valves out and back in plus substitute if you have known good spares, as a start point. 

sgosden

I think I've got some spare pre amp tubes, I'll swap the 4 out and hope for the best! 
If not it'll go to a tech. 

@ICBM - the dsl has done me very well I won't hear a bad word against it ... /I can't afford a JCM800 that I really want .