Tube amp failure

[Funk is]

I am a bassist first and foremost so I hope you can take that into account.....at my gig, where I play both bass and guitar, one of my tube amps had an event, and it doesn’t seem like a tube.

The amp that failed was my 15watt blues junior- brand new. I had the master at about 2 and the volume around 7 and after about an hour or so the amp “shut down”.

I first heard the signal weaken, then crackle for a few seconds the TOTAL SHUTDOWN- the amp was off; no light, no sound, and no smell. The amp was plugged into a common outlet which shared my bass amp and was playing fine, so power supply was steady.

After 10 minutes or so it played as if nothing had happened.

What’s the deal? 10pts. For correct answers

 

[Mr. Foxen]

Lots of things could make it do that. More investigation needed. Cracked solder joint/bad connection would be my suspicion.

 

[agedhorse]

Most likely a bad tube that caused subsequent issues (collateral damage). Since it's new and presumably still under warranty, don't mess with attempting an internet aided repair. Contact the manufacturer's service department and ask them how to get your amp repaired under warranty. IME, Fender's service network is very good and will take care of you.

 

[bobyoung53]

First it sounds like it started drawing too much current (bad power tube?) but that is strange that it shut down completely and then started working normally after 10 minutes, something heat related I would think, I checked online to see if it had a circuit breaker but it has a fuse, but yes I would have it checked under warranty.

 

[BassmanPaul]

If your amp is indeed brand new it has a warranty. Return it and get one that works.

 

[Funk is]

I know it’s under warranty but I just want to gain some perspective on the issue if possible. Thanks for the thoughts and advice, that’s what i’m here for. I’m not a good consumer really so before I “send it back for a new one” I wanted to be sure it wasn’t something in the power chain before the amp. More details:

it was plugged into a 15A power strip along with my bass amp, pedal power block and an effects unit. Both amps were at low volume (20%).

I played it today with more volume and a looper pedal for over an hour and no issues. Plugged directly into the wall socket. All the tubes glowed normal. Upon first playing though there was a low pitched crackle for a minute or so, at first I thought it was a rattle somewhere in the cab, but it disappeared. The amp was warm to the touch but I guess that is normal with tube amps?

It Made my hollowbody guitar sound really nice and carried the looped rhythm track without any flatulence or mud.

 

[bobyoung53]

I know it’s under warranty but I just want to gain some perspective on the issue if possible. Thanks for the thoughts and advice, that’s what i’m here for. I’m not a good consumer really so before I “send it back for a new one” I wanted to be sure it wasn’t something in the power chain before the amp. More details:

it was plugged into a 15A power strip along with my bass amp, pedal power block and an effects unit. Both amps were at low volume (20%).

I played it today with more volume and a looper pedal for over an hour and no issues. Plugged directly into the wall socket. All the tubes glowed normal. Upon first playing though there was a low pitched crackle for a minute or so, at first I thought it was a rattle somewhere in the cab, but it disappeared. The amp was warm to the touch but I guess that is normal with tube amps?

It Made my hollowbody guitar sound really nice and carried the looped rhythm track without any flatulence or mud.

Crackling is not a good sign, could be incorrectly set bias or something worse, I would get it checked before something goes poof.

 

[rodl2005]

Old school, and thus, totally legit....
Bang it on the top.

If that doesn't work, and I can't see why it wouldn't, it worked for The Fonz

Then , have you tried switching it off then on? Or, re-booting?

 

[agedhorse]

Crackling is not a good sign, could be incorrectly set bias or something worse, I would get it checked before something goes poof.

Incorrectly set bias does not cause crackling.

This is the sort of problem that should be handled by the warranty process, messing around with repair attempts is one way to void a warranty too, something the OP should be aware of.

 

[Bertr]

If it is that one https://www.thetubestore.com/lib/th...r/Fender-Blues-Junior-III-Schematic-Rev-D.pdf

Well 'No lights' as you mentioned pretty much means no voltage on the filament side of the Power Transformer.
But it was working later, so all fuses are OK, and Power Transformer is also fine.
I would first think of the connection between the mains plug and the power strip (230 or 120 depending on your location) during the gig. It happens (don't ask).

 

[Funk is]

I spoke to a warranty tech. Berter’s Post is about what the tech told me. The fact that the amp played fine afterwards means either than it fixed itself or the mains supply was the issue. He recommended I play it and if anything else happens bring it in. I’ll keep this thread updated for the benefit of all.

And I agree it isn’t wise to do “internet fixes”, but I think everyone who posted brought some honest experience and valuable thoughts. It certainly helped me in weighing my option(s). Thanks!