Amp Problem

moster78

Figured I'd post this question before I bring the thing into a tech.

My Fender Vibro Champ is having issues. After playing for about a half hour, the thing just completely cuts out. No sound whatsoever. So far its done it twice in a row. I've checked the speaker connections and everything looks solid. What would cause it to just stop working completely after 30 minutes, and then start a few days later on my next attempt. Something overheating? Any thoughts would be greatly appreciated.

xtremehardy388

Overheating might have something to do with it. Check the tube connections. It might be a solder going. Is it 30 minutes both times?

ianvomsaal

How old are your tubes???
How old is the amp???
Have you had any work done to it since you bought it???
Parts in tube amps get old and need replacing over time - You may need some caps replaced.
And if the tubes are old and have a lot of play time on them they may be on their last legs.

- Ian

moster78

The amp is a '74 Vibro Champ that I bought last December off Craigslist, so I have no idea how old the tubes are. I think I'm just going to bring it to a tech to get looked at and see what's wrong with it. I just have no idea where to find a good one on Long Island. Haven't had the best luck with shops lately.

who's_pearljam?

I doubt it's a tube problem that makes it cut out like that, but it may be time for tubes anyway.

When it cuts out, are the tubes still glowing? If they are, then you know you're getting power that far, anyway. If the tubes cool down, then the problem is somewhere near the power input.
If the tubes are still hot, then it'll be a connection or a bad part after the power section. If that ;s the case then don't run it again, because the amp can burn out if the power's not getting to the speakers. Maybe try a different speaker cabinet if you have one around? Just run a cord from the output to the input on your other cabinet (You must! You're collecting some cool gear! )

You may have a loose connection or solder joint in there. When the amp heats up then the metal expands and contracts, so a loose connection could disconnect and shut the thing down, then when it cools, the part contracts and reconnects. (Who's_pearljam?'s third law of physics)
Even some fuses can do this. They get jostled around and have loose elements inside and can be erratic. If that was the case, then the tubes would be shut off when this happens, too.

This usually happens during your best solo during a gig. (Who's_pearljam?'s FIRST law of physics!)

Try replacing the fuse for the heck of it, and see what happens if the tubes go out when it cuts out, and check the connections where the power cord connects. After that, then you need a tech to go through it and find the bad part, unless you're electrically proficient.


Ok, get a tech!

moster78

I was trying it again today, and again, worked for about 30 minutes or a little later, then cut out. The tubes were still glowing in the back, but possibly not as bright as they were when I switched it on. I got the name of a great guitar tech from a friend, and a few of my guitars are in dire need of a setup, I'm going to ask him if he does amps or know anyone that does. Any other thoughts though?

exhausted

wild guess here:

something warming up, thus expanding, thus breaking a connection somewhere?

first check is always new tubes though.

lucylespian

Sounds very much like a dry solder in the PCB to me. My H&K did sometihgn very similar this time last year, it had dry solders.

Sounds like tech time to me.

moster78

Well, I've narrowed down one thing, I have a bad cable. Tried my stuff into my other amp and a no go, tried a different cable and it all worked fine. But, I was having the same issue last week with the Vibro Champ with a different cable.