Fuse replacement for guitar amp

My fuse in my guitar amp blew and need to replace it. The writing on the amp states F3AL. I pulled out a 3AB 3A 250V ceramic fuse. Other writing is Bel EJET 125V

I know F3AL is 3A fast acting low breaking capasity. I just don’t know much about the breaking capasity.

The fuse is 30mm


The below link of fuse options were found.

@Kimura Sounds like this one:

Bel Fuse Inc. 3AB 3-R

Does the breaking capasity need to be finite? It’s difficult to find info on breaking capacity.

The only formula I found on low breaking fuses is 10x the rated amperage or 35A which ever is better.

Hi Kimura,

I’m not sure what you mean by your question. An ideal fuse would have infinite breaking capacity, but that’s not possible. All fuses have a breaking capacity (also known as the interrupting rating), as it is a matter of the physics of the device. That spec refers to the maximum current a fuse can safely interrupt. Anything above this can have unpredictable results, including uninterrupted arcing and/or physical destruction of the fuse body, possibly including explosion.

The breaking capacity for the 3 Amp 3AB fuse is 100A at 250V or 10,000A at 125V, as rated by UL and CSA. This comes from the Safety Agency Approvals table on the first page of the datasheet.

From the datasheet of the Bel Power Solutions and Protection 3AB series fuse

Hi @Kimura

Have a look at this resource: Fuse I2T Rating, Melting Point, and Interrupt Rating

So if it has a higher rating that’s stated for the equipment, it’ll work just fine? That’s what I get from reading ryan’s link.

All else equal, higher interrupt ratings are “better”; ceramic fuses will often have higher interrupt ratings than glass fuses.

More important things to match are, in order:

  1. Physical size
  2. Current rating
  3. Response time (fast, slow, etc.)

Dave’s suggestion is good, but most any fuse matching on the above 3 points should do.

Note that if a fuse has blown, that’s often a sign that further damage has occurred, and that additional repairs will be needed.

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@Kimura -san
It’s so true.

I have an experience.
My Guitar amp was pretty expensive and old 2 x 6L6 Tube amp and 4x10 speakers.

But it blows fuse a lot.
One night at the club, every band member looking at me and said,
“Hey, is that your raggedy amp? Smoke comes out!”

Then I found resistor and PCB was burned.
I thought unstable power condition where I was. (That caused terminate another friend’s Synthesizer too).

Afterwhile, I was asking one of my friends who owned repair shop in Japan (That time I was in the States) and said,

“You know what? That guitar (amp) company didn’t clean Solder bath that’s why. Then contamination caused soldering point weak. Many customers bring same trouble to my shop. So, I have to remove old solder and clean the board and put fresh solder again.”

So, In that case, he needs to check up like Rick-san said.

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