Marshall MG15DFX clicking andpopping when turned on

[BobJ1973]

I've recently purchased this Amp secondhand for practice, and noticed when its turned on it has a loud clicking and popping for a few seconds, but then works fine.

Is this normal, and if so, are there any mods to improve this.

Cheers
Bob

[52 Bill]

It certainly doesn't sound normal to me. Is the noise effected by any of the controls? If you give the amp a good thump, does it cause the amp to make the noise?

[BobJ1973]

Its only on initial switch-on and when switching-off.

I get the impression its the power amps causing the problem, and I'm sure I read somewhere this is due to the amps being unbalanced for a split second as power is applied or removed.

Just wonder whether any other owner could confirm whether this is normal for this design, and if there is any mod to improve the situation.

No amount of banging about replicates the problem, so I'm sure it not a bad connection or dry joint issue causing the problem. It seem likely to be either a design issue or possibly a component starting to breakdown, maybe a decoupling capacitor or something similar.

[52 Bill]

Maybe a problem with the mute circuit. I think there is a small electrolytic cap on the power chip board that controls this.

Search past posts, I seem to recall Enzo discussing this before.