Vintage 1959 Super Lead Fuse Size - Mains 2a or 4a?

cap217

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I always assumed 100w marshalls were 4a main and 1amp ht. But after looking at a bunch of pics of old amps I see a lot of 2a main stickers. I thought these were for overseas voltages but these were on US amps. Is it safe to assume that these amps were from overseas and people didnt update the sticker or even the fuse?



Also, on a 1980 jmp 2203. I went back to 6550s which the amp is setup for. What size fuse should I be using? Is it different with 6550 vs el34?
 

TAZIN

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The general rule of thumb is the lower the AC voltage the higher the amperage...So, USA amps run a 3 or 4 amp mains fuse & a 1 or 1.5 amp H.T. fuse. England amps run a 2 amp mains fuse and a 1 amp H.T. fuse.
 

Matthews Guitars

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Be aware that UL rated fuses have slightly different real world values than IEC/CSA/whatever you call it ratings on fuses in Europe.

If you use a UL rated fuse, you'll want to use a slightly larger rating.

For example, the 1A HT fuse in a Superlead may blow every so often if it's a UL 1A fuse. So go to a 1.25A UL rated fuse and that'll hold unless there IS a real fault.

That is exactly the situation with my own Superleads. I've never had cause to change the mains fuse but the HT fuse, if it pops at 1A, gets a 1.25A UL rated fuse and that's just fine.
 

racerxrated2

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Funny story-
When I received my 72 Trem, I’d play it at volume for 10 minutes then POOF goes my fuse. Popped another in, same result. I was thinking great, the pt or tubes are toast. Then I realized that since this amp came from England, I bet the fuse is still expecting 240v. Switched from 2A to 4A and no worries. But I was in a panic mode initially worried about the Transformers.
 

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