Blowing Fuses

[charvel750]

Guys, I have a JCM 800 2203 Reissue that keeps blowing the 1A fuse. All tubes light up but no output and the fuse blows within seconds of turning off standby. What does this generally indicate when the 1A fuse blows? Thanks...

[Rsmacker]

Check your speaker cable.
The 1A is the HT fuse, right? Are you sure your valves are OK? Do you get any sound out of it at all?

[wilkinsi]

You sure it's the correct rated fuse? I had a pair of powered monitors (Dynaudio Acoustics BM5A's) which will only take 1.5a that kept doing the same thing. Otherwise, I'd probably be looking at getting the internal power supply replaced.

[jacksonaxes]

With my VHT it was a power tube.

[DonP]

Power tube.

Sorry.

When I got my DSL100, one tube went bad right off the bat. I replaced just that one tube (since the other three were new) and have been running that way ever since.

[charvel750]

Well, it is the HT fuse, 1A. But I tried different sets of known to be good quads and that's not it either. Weird, when you move the chasis around a little there is a plate reading on the meter, but then it dies out and no output. Weird.

[jacksonaxes]

Sure sounds like a filament in a tube.:think:

[Spivonious]

Time to take it to the shop. If the fuse keeps blowing and it's not a bad tube, something is wrong with the amp.

[DonP]

Well, it is the HT fuse, 1A. But I tried different sets of known to be good quads and that's not it either. Weird, when you move the chasis around a little there is a plate reading on the meter, but then it dies out and no output. Weird.

Here's your next step.

Pull ALL of the tubes.

Power it up with a good fuse.

Does it blow? Did the B+ voltage fail?
Yes -> Amp tech (I'm guessing/hoping it's only a shorted power cap)
No -> bad tube -> continue

Power down.
Put in 1 tube.
Power up.
Check fuse an B+

Repeat until you find the tube that's killing fuses.

[Shawn Lutz]

I would tend to think its probally one of two things. A bad output tube or transformer...hope its not the transofrmer..

oh and just for reference, my original JCM800 2203 (84 model) had the exact same that is happenig to you thing happen to me....it was the tranny in my case. I'd have to dig out the repair reciept to be 100% sure of that... if I stll have it

[DonP]

I would tend to think its probally one of two things. A bad output tube or transformer...hope its not the transofrmer..

oh and just for reference, my original JCM800 2203 (84 model) had the exact same that is happenig to you thing happen to me....it was the tranny in my case. I'd have to dig out the repair reciept to be 100% sure of that... if I stll have it

That's why I said "hopefully it's just a shorted power cap", because a blown tranny would suck.

[DonP]

Guys, I have a JCM 800 2203 Reissue that keeps blowing the 1A fuse. All tubes light up but no output and the fuse blows within seconds of turning off standby. What does this generally indicate when the 1A fuse blows? Thanks...

Turning off or turning on standby? Describe this better - what causes the fuse to blow.

Also, what year is the amp? How old?

[Cygnus X1]

Fight the good fight DonP.
Sometimes I get tired of Internet troubleshooting.

If I see something wonky I'll try to muddy up the waters a bit.

[charvel750]

What are you guys talking about? If the amp is ON standby, it's not putting out sound. You have to take it OFF standby and actively engage it. Thought I was pretty clear about that. So no waters need to be muddied, I've been around and know a thing or two.

It's a 2004, so 6 years old. It's definitely not the tubes, so if it is the transformer, I assume that's around $100 to replace, plus labor and time to have someone install it?

[Cygnus X1]

So no waters need to be muddied, I've been around and know a thing or two.

My comment wasn't directed at you in any negative way.
More directed at myself for being to lazy to look it up.