Amps blowing fuses. Please help.

[TBirdMcSka]

Hey guys, I'm new here, and very new to working with electronics so I was wondering if you could help me out out.

I have a Crate GT1200H guitar head and a Gallien-Krueger BP250 bass head that both keep blowing fuses.

The Crate has 3 different fuse ratings listed on it. 1.6 amp, 3 amp, and 4 amp.
I tried a fast-acting 3 amp fuse and it blew as soon as I turned it on.

The GK has 2 different ratings. 1.25 amp and 2.5 amp. I put a fast acting 2.5 amp fuse in and the exact same thing happened.

Am I using the wrong fuses or is there some other problem?

[pdf64]

Does the fuse rating list have T or F alongside the values? F means fast acting/quickblow, T means time delay/antisurge. Fuses in the mains circuit are most always T rated, F types of same value will blow straight away. Peter.

[jrfrond]

You can tell a lot by HOW the fuse blows.

If the inside of the glass cartridge has blackened, it means that the fuse link exploded quickly due to a dead short, most likely due to a shorted semiconductor either in the power supply or power amp.

If the link just melted open in the middle, then it indicates an overload or "soft short". Repeated blowing of fuses indicates a circuitry problem and not a simple overload. Even fast-blow fuses should at least power it up.

In either case, since you are new to electronics and I am not, I respectfully submit that, with solid-state amp problems such as this and not being educated in the required troubleshooting techniques, you are probably in over your head, and that this forum is likely beyond the scope of your issues.

[TBirdMcSka]

Does the fuse rating list have T or F alongside the values? F means fast acting/quickblow, T means time delay/antisurge. Fuses in the mains circuit are most always T rated, F types of same value will blow straight away. Peter.

Haha, I just checked and they both have T's and the fuses I was using were both fast acting.
I think you solved my problem.
Thank you sir.

[Dave Curtis, dB AudioTech]

Haha, I just checked and they both have T's and the fuses I was using were both fast acting.
I think you solved my problem.
Thank you sir.

Most solid state amps (all?) that I've ever woked on had fast-acting main fuses, where tube amps tend to use slo-blo types and fast-acting for the HV (B+).