Did I blow it up??? Problems with marshall JCM 2000 DSL 401

[corduroyew]

I barrowed a Marshall JCM 2000 DSL 401 from a friend the other day. I plugged my guitar into the clean channel with the volume and the master volume both two thirds of the way up. I strummed the guitar one or two times and then it started crackling like I had a short in my lead. After that it got a screachy sound followed by some clicking and then silence. here is a sound clip The 400ma fuse blew, but I’m not 100% sure the fuse was the only problem. What do you guys think? Should I change the fuse and see what happens? It’s not my amp and I don’t want to mess anything up any more than it already is, but at the same time I’ve been given the all clear to poke around in it. What do you guys think happened?

[drewl]

sounds like an output tube died.

[Enzo]

I agree. THE MOST common reason for that fuse to blow is a bad power tube.

[corduroyew]

Is there some way I could check the tubes to see which one went bad and then replace it?

[Mars Amp Repair]

I agree also as would most that the power tubes are the 1st & highest suspect. You could remove all the power tubes, replace the fuse, & then try it. If no fuse blowing, better chance it's the power tubes.

As far as checking the tubes, sometimes it takes the tube heating up for a while under the current & voltage conditions they have in the amp, before the short shows up.

Tube testers rarely put the same strain on the tubes as the actualy amp does. So, the tube tester isn't always the definitive answer.

You could replace the fuse & once the tubes are warmed up, throw the standby switch & watch to see if it is sparks from the power tubes that occur, then quickly turn back to standby. Chances are the fuse will go before you ever switch it out of standby.

Also, sometimes you have to tap the tubes to get the short to show up.

You can choose one of those scenarios, or just replace the power tubes, as that's the most likely culprit...don't forget about biasing.......glen

[Enzo]

You COULD try to find which tube had failed. But really, all four tubes are equally old and have had equally stressful lives.

If you had four bald tires on your car, and one of them finally wore through and went flat, would you feel safe just replacing that one?

You realy should consider a whole new set of power tubes.

[corduroyew]

Ok, thanks guys. So now I gotta ask, what was the sqealing that I heard? Is that just the sound of a fuce melting?

[Amp Kat]

Amps make all sorts of strange noises when malfunctioning so I wouldn't worry about it. Lets just hope that nothing happened when the tube went because this amp has that reputation for it so after replacing the tubes all the problems should hopefully dissapear.

[corduroyew]

Ok, thanks for the help. I've ordered some tubes and I'll let you guys know how it all turns out.

[Mars Amp Repair]

Yep...universally agreed...when you find a bad power tube, you replace them all! Good luck...glen