Any Idea what might have happened with my amp?

[Surgeon]

So, 2 days ago I'm up to jam with a band that's looking for a singer and a guitarist... So I'm applying for both positions... Anyways, I bring the amp in (JCM 800 4210 50 watts combo), plug it in, let it warm-up, turn it on, no problem. Then, I try to crank it louder, turn the master wayyyy up (a little too much I must confess) strike a note and the whole thing just cracks and lowers volume A LOT. So I unplug the thing and borrow a Crate ss combo (about the same thing I'm trying to get rid of right now... :smack: ) Play the jam....

So today I deceide to have a look at it before bringing it in to a tech, I changed the tubes about 4 months ago and never gigged/jammed with it so I figured that I might have done something wrong (altho I did play it a lot inside without problems but never at high volumes)... Look at it and if I can't fix it or see what's wrong I'll just bring it in.... Well, that damn thing works fine now...

Anybody has an idea what's (was)wrong with it? It might not have liked the car ride... I found out that the fuse was sticking out this morning, plugged it back in and it worked. I'm not a tube amp guru so please give me a little help here, I'd really appreciate. I don't want to waste my money on a tech to find out nothing was wrong but I don't want to damage the amp either...

Thanks again in advance guys,

Phil

 

[Kent S.]

Re: Any Idea what might have happened with my amp?

I'd go thru and check everything for loose connections first, then check it at loud volumes at home, leave in on for a while, let it heat up some. Cold solder or overheated solder joints (as in a connection trying to carry to much current) can do little power drops like that, so can loose connections on the tube sockets, or other connections. Get yourself a small surge protector (ala Radio Shack ...plus it's convient to plug in pedals and such) if you don't have one already, and one of those receptacle plug in testers that show if the receptacle that you are plugging into is wired correctly.
Watch you tubes, hit some power chords loud, dirty and clean ... if you see anything odd like arcing inside the tubes (okay turn down the lights if you have to), then shut the amp down and get it to a tech ASAP, as there may be other damage getting ready to really damage something.
A further trick that you can do to help protect things is to get some fuses, of lower ratings (not higher, and I'm referring to the Amp rating, smae type fuses also), and exchange them ... lower and lower, they blow sooner, but if you can find a medium where they blow, not to often ... you'll have much better protect if something decides to go ...this is generally not required if your amp has B+ fuses. Really it's a hard call Phil, best thing is if the filter caps (big caps) look okay (don't touch them, they'll knock the crap out of you, so be careful ... you might want to do that trick of leaving the amp on and *unplugging it from the wall {stepping on the power strip on/off button} while still playing guitar, to drain down those caps*. Not a whole lot of help, that's about all you can go on at this point.

 

[Robert S.]

Re: Any Idea what might have happened with my amp?

Sounds like a few things. Wiggle the guitar cord in the input jack. If the input jack is mounted to the board or failing the amp will do that. I had a bad input jack in my JCM 800 2203 head and it did exactly the same thing. My 800 doesn't have the jacks mounted to the board so it might just be the jack. The jacks for those are inexpensive and common.

The fuse might have been loose and you weren't getting full power.

You might have a ghost. Weird things sometimes happen for no reason with gear.

Check all your cables.

But a bad jack made my 800 do exactly what yours did, cracking and low power.

 

[Surgeon]

Re: Any Idea what might have happened with my amp?

Thanks Kent! I know it's a tough call, that's why I asked here... I'm going to try it again next time, I always try to let the tubes warm-up properly... Anyways, I'm going to try to check the tubes while I'm playing next time. I didn't mess with anything in this thing, except for the tubes, I'll take a peak inside to make sure everything looks ok too...
Thanks for the help, I really appreciate it!

 

[Surgeon]

Re: Any Idea what might have happened with my amp?

Sounds like a few things. Wiggle the guitar cord in the input jack. If the input jack is mounted to the board or failing the amp will do that. I had a bad input jack in my JCM 800 2203 head and it did exactly the same thing. My 800 doesn't have the jacks mounted to the board so it might just be the jack. The jacks for those are inexpensive and common.

The fuse might have been loose and you weren't getting full power.

You might have a ghost. Weird things sometimes happen for no reason with gear.

Check all your cables.

But a bad jack made my 800 do exactly what yours did, cracking and low power.

Thanks Robert! (I think we posted at the same time...) I'll check the jack for sure, that looks like a possible explanation... Same thing with the fuse, the "holder" doesn't look really healthy, it might have come loose during the trip and the fuse might have poped out from vibrations when I played...

That's great info and help guys,

Thanks again Robert!