what causes the HT fuse to blow in a marshall?

[Dreamland_Rebel]

my buddies marshall keeps blowing the HT fuse. any ideas why?

[Rsmacker]

Almost certainly a fucked output valve or possibly speaker connection. Find out, the fuse is a VERY IMPORTANT protective device. You don't want to be replacing trannies!

[DonP]

Bad tube as was already said.

Want to fry the amp? Wrap the fuse in aluminum foil and stick it back in. Might want to get far enough back to avoid the flying debris.

[roodyrocker]

What is the HT fuse? I used to have a mid 70's non-master volume Super Lead 100 Marshall head that would blow fuses as soon as I went off standby and hit a chord. I'd take the head in for rePair only to have the problem recurr as soon as I took it back home. Turned out to be a loose jack on the 4x12 cabinet. Once that was replaced the head never blew another fuse!

[jtr]

Bad playing.

[Rsmacker]

What is the HT fuse? I used to have a mid 70's non-master volume Super Lead 100 Marshall head that would blow fuses as soon as I went off standby and hit a chord. I'd take the head in for rePair only to have the problem recurr as soon as I took it back home. Turned out to be a loose jack on the 4x12 cabinet. Once that was replaced the head never blew another fuse!

The HT (High Tension) fuse protects the transformer from excess current which would be caused by a fucked valve shorting out, or if you are driving the amp without any load connected.
Depending on the age of the Marshall in the OP, the problem will be as already pointed out, or if it is an oldie, maybe something like a cracked valve base.

[Da' Melta']

Bad playing.

:ROTF: