Xiderpunk

My DSL-50 has developed a problem.. after a few minutes of playing sounding absolutely fine it starts producing a loud hum and no notes. Only way to stop the earsplitting hum is to turn it off adjusting volume makes no difference. This has occurred since a recent tube change. I have tried swopping tubes to the older ones and still the problem occurs. The bias is correctly set and double checked. I have tried my best to clean the contacts on the tube sockets.

I am about to send it by expensive courier service to Marshall to investigate, but just before I do anyone have any ideas or seen this happen before?

I am at a loss as to the cause and not sure if I should be checking something else?

Warm regards,

Chris

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Marshall JCM2000 DSL-50 with 1960A 4x12 (2 x GT-75's + 2 x Vintage 30's)

V1: NOS Mullard 12AX7
V2: Sovtek 12AX7-EH
V3: JJ ECC83S
V4: JJ ECC83S
Power: JJ KT77 or JJ EL34L


http://www.myspace.com/taintedgraceband

steelhorse

You already have your problem partially solved. You indicate that this started after a tube change. Change the pre amp tubes back one at a time (that is if they themselves were changed) and see if this helps.

If not: Then try replacing the power tubes 1 at a time until you resolve it.

Get the bad tubes replaced under warranty.

Re-bias the amp if it you do wind up replacing the power tubes which brings up another important question:

note: Did you re-bias after the tube change? You need to check the bias FIRST if you have not done this step.

visit Eurotubes for their how to bias video clips and bias information.

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