Marshall JCM800 mo. 2210 power fuse

[Randall]

Oh boy. A mint 80's 2210 comes in, looking like it has been sitting for decades. Original everything. Cleaned it up, tested tubes, tweaked bias, good to go. Except it had a T4A power fuse, the back of the amp and schematic clearly indicate 2A. I thought this odd for a 100 watter, but swapped it to a 2A.

Two hours after he gets it home, guy calls me, saying it blew it's fuse. Whoops. I do some digging and end up thinking perhaps the amp came from a 220v country, where a 2A fuse would be appropriate. I decide the 4A needs to back in it. While I am doing this, he calls a shop in Nashville, who asks him what year it is. He tells him (1988 I think), and the guy laughs. Seems that year Marshall put a little 4A sticker over the painted 2A for the fuse. The stickers fall off, leaving the wrong value showing!

This turned out well, but I did not know any of this. At least my suspicions about a 2A fuse in a 100 watt head were correct.

The schematic doesn't show any variation for line voltages, only a T2A for the mains fuse. Not sure what's up with that.

[g1]

That's interesting. Never looked closely at the schematic I have. It does show T2A, but does not specify the line voltage. But it shows the voltage switch in the 240V position.
We did have a thread the other day where the model number on the rear plate did not match. The fuse stickers where still on but it seemed the model number sticker had come off.

[Jon Snell]

Marshall amps originally, were made for the UK market and when multitapped primary windings were required for other countries it was decided not to reprint the rear panels so, 2A for 240volts; 4A for 120v and 5A for 100v. Smaller amps; 1A for 240v, 2A for 120v and 3A for 100v, (100v for Japan).