Guitar amp sounds like an old FM radio?

[Contract Killer]

Ive got a Marshal DSL15C guitar amp, which i had been really impressed with, however yesterday it all went wrong

On the ultra gain channel it sounds like an old FM radio thats not quite tuned in....
Even with no guitar plugged in.

It gets louder with volume or gain.


The clean channel is fine.

Anyone any ideas what could cause this?

[jensenhealey2]

Possibly a valve has died in hte gail channel pre-amp and needs replacing..

[bga]

Do you have any new electrics devices running?

I had similar with my day-to-day Laney. Tried my Boogie and the same. The culprit is electrical noise from the lights in the cooker hood.

[Contract Killer]

Thanks, ive tried tapping the valves and there is no sound transmitted to the speaker.

If i remove any of the 4 preamp valves it makes no sound at all.


No new electrics, it just suddenly started doing it. However i guess it could be the amps power supply?


Its only 6 months old, so would expect valves etc to be ok really.
It is under warranty, however was bought online, so wilk be a bugger to return with the weight/size. If there was an easy fix i would just rather do it.

[JLC25]

Contract Killer said:

Thanks, ive tried tapping the valves and there is no sound transmitted to the speaker.

If i remove any of the 4 preamp valves it makes no sound at all.


No new electrics, it just suddenly started doing it. However i guess it could be the amps power supply?


Its only 6 months old, so would expect valves etc to be ok really.
It is under warranty, however was bought online, so wilk be a bugger to return with the weight/size. If there was an easy fix i would just rather do it.

I really would not stick your hand in the back of an amp - have you tried running it on an isolated power supply?