Bassbreaker 15 head, valves gone or not?

MazzaG

Hi all,

I have a Bassbreaker 15 head and I am pretty sure one of the valves has gone kaput, I just wanted someone else to confirm before I replace it. It's my first tube amp and this would be my first time troubleshooting this issue.

When I turn it on (connected to cab) it makes a horrifically loud noise that I can only describe as a motorbike engine revving and getting progressively louder. Turning the master volume (or any knob) has no effect on the sound, it's just as loud. As you can see in the photo below the left valve isn't nearly as lit up as the right, it must be this one? I can't do the tap test because of the horrible noise the amp emits when turned on. 





The only reason I am confused here is because of the noise described above, it doesn't seem like a typical symptom of a bad valve. I'm happy to record a video of the sound but it'll have to wait a bit or my landlady will have a coronary. 

Lastly can anyone recommend a replacement? Should I replace the lot or just the one? Bassbreakers are equipped with EL84 tubes. 

ICBM

I can't see those pics, but it could be either valve, unless the 'bright' one is really glowing too brightly in which case that's the faulty one, not the dimmer one.

I'm pretty sure this is a cathode-biased amp in which case you must do this test only very briefly (only a few seconds if possible - it's bad for the other valve), but remove one valve and power it up. If the noise doesn't happen then you've got the bad valve out. Repeat with the other valve even if that is the case. If one valve appears to be the cause, put the 'good' valve where the 'bad' one was and try again to eliminate a problem with the socket.

If you can definitely isolate it to one valve, replace both and keep the good one as a spare - but don't spend money on new valves until you're as sure as you can be that it's definitely a valve problem. I would get JJs as they appear to be the most reliable current production EL84s.

MazzaG

@ICBM Thanks for such a detailed reply. I followed your instructions to a T and appeared to have isolated the dodgy valve .....however when I put them back in the amp is working fine!? 

The only thing I can think it was is they weren't in the socket properly, although those pictures I posted they look nice and stuck in. So confused :-/  I see no reason as why one may have become dislodged..it's literally the first time I have opened the amp and it stays in my room. 

MazzaG

Although having checked again the least brighter of the two is now not even lighting up, yet I'm still getting guitar sound through the amp; can amps still emit sound with a single working valve?
. Think I am just going to order a new pair for peace of mind.

ICBM

MazzaG said:

Although having checked again the least brighter of the two is now not even lighting up, yet I'm still getting guitar sound through the amp; can amps still emit sound with a single working valve?

Yes, although if you turn it up more it will sound quieter than normal and oddly distorted.

MazzaG said:

Think I am just going to order a new pair for peace of mind.

Probably the best plan. It does sound like it's not an amp problem at least.

MazzaG

Set of JJs ordered, thanks again mate appreciate it.