Bad pre amp tubes?

[DawnPatrol1990]

Hey guys

I've got a Marshall JMP-1 that i bought to use use for guitar and occasionally bass as well but the drive on it is really bad, even at full gain it barely makes an ACDC crunch sound. Does this seem like the pre amp tubes have given up?

Thanks

[luckydog]

Perhaps, but you'd need to be lucky, those tubes are pretty reliable normally. You could swap the two 12AX7s over and see if it makes any difference at all, if not then the tubes are prob fine. HTH !

LD

[Dan Dare]

Be a bit careful DIYing on tube amps. The internal supply voltages can be pretty high. Best to take it to a pro unless you know what you're doing.