hamer

There's no sound coming from my amp at all, no poping, no fuzz, just silence.It's a JCM 2000 TSL 100,I bought it new a few years ago. It was working fine today for a couple hours and then I set my guitar down with the volume off and forgot to turn on the stand by on the amp head,came back an hour later and nothing would come out, tried a different guitar and cables still nothing at all on any of the channels.Only problem I've ever had with it is that I think it over heats I've had to put a fan on it after a few hours of playing and then it would work fine,but now there's just nothing.

Any thoughts would be appreciated.Thanks.

RiverRatt

Check the HT fuse.

hamer

The HT fuse was the problem. Do they just blow sometimes? The manual said that if the HT fuse blows it could mean that an output valve has failed,if that's what the problem really is are they expensive to fix?

RiverRatt

Glad I could help. It could have been a power surge or a spike. I wouldn't worry unless it keeps blowing fuses. Also, make sure the tubes are biased to the acceptable range for your amp. There are tons of bias threads already, so I won't go into the DIY process, but it's easy.

If you decide that you need to replace your power tubes, my favorites are the Groove Tubes EL34M Mullard reissues. SED Winged C's are good, too. Either of these will cost you around $100 for a matched quad. If you're on a tight budget, the Electro-Harmonix EL34EH's are decent sounding tubes, and they are around $50 for a matched quad.

hamer

The fuse blew again and I can see one of the small tubes is not lit up,is there a safe procedure for replacing tubes,can you get shocked when you do it?

stryker59

theres no harm in pulling the tubes from their socket and putting them back in.....it works best for the big bottle power tubes to grip them at the base when pulling them out.
you can get seriously electrocuted if you take the amp chassis out to bias it......even when they are off the caps store a ton of energy! so you gotta be careful!

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Adwex

Replace the bad preamp tube (12AX7), replace the fuse, you'll probably be fine.

No danger pulling the tube, just treat it like a light bulb. Just grab it gently but firmly by the glass, wiggle it a little as you're pulling up. Don't touch the pins when you're pulling it out.

Be careful inserting the new tube, don't screw up the pins. There's no "key" like power tubes have, you have to line up the gap with the gap on the socket.

As stryker warns, stay away from the big capacitors.

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hamer

Ok it blew again.What should I do?Replace all the tubes?If so, do I have to have it biased?All the tubes glow when the amp is on but can tubes still be shot even if they light up?

RogerAF

I have had HT fuses blow because of a bad power tube--the head had 6550s. If you have extra power tubes, try replacing each tube one at a time (you'll need a supply of HT fuses). If you don't have any extra tubes, you can pull two of the ones in the amp. Make sure they are either the two outside or the two inside. (This is often done by people who want to run the head as a 50W.) If there is one failed tube then one of the configurations should work. If it is something else then this won't change anything.
Good Luck.

stryker59

if the fuse is blowing it is a sign of a bigger problem....may be time to take it to a tech

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