i am running my guitar through a peavey 5150 blockletter head and an emperor 4x12. the cab is loaded with four 8 ohm celestion v30s. i have the impedance on my head set to 8 ohms.

i just recently got this cab. i have had no problems with my head before this. earlier today, my band was running through our set and my head just would quit producing any sound. i thought it was my guitar at first because the amp seemed to still be on and running fine, but i found if i turned off my head and gave it a few minutes and turned it back on, it would play find again for a few minutes and then do the same thing.

before the show, i went and got a new speaker cable and also picked up a small fan. while we played, i ran the fan blowing directly into my head. i had zero problems during the whole set at all while the fan ran. is this a problem with the cab? or is my head just overheating or something? the problem seemed to have disappeared when i played with the fan blowing into my head but the problems also seem to have coincided with my getting this new cab. any ideas?
Is your amp bias modded? Maybe the bias is set too high.

I doubt it would be a problem with the cab making it overheat. That would just fry the output transformer and then you wouldn't be able to get sound at all.
Quote by Dave_Mc
I've had tube amps for a while now, but never actually had any go down on me
Quote by jj1565
maybe you're not saying the right things? an amp likes to know you care.

Depending on how the speakers are wired together, you may be running at the wrong ohm rating. Like 4 8 ohms speakers run in full parallel or full series may cause the cab to be something rather than 8 ohms. But I'm not sure if that would cause it to turn on and off.

Seeing as the fan helped I'm not really sure if it is an individual tube that is the problem, which was gonna be my first guess... But you could try changing the power tubes...

Sorry I can't help much... but I guess in the mean time keep the fan nearby...lol
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Like said, it depends on how it is wired.

OR - it could be something else entirely, but this would help you rule something in our out as a possible cause.

See if this helps:

So if it is the latter, Series-Parallel wired, you should be OK. Otherwise, you may need to set your amp at 4 ohms. A quick way to check would be to get a multimeter and set the pos/neg tips on the other end of the speaker cable, the end that plugs into the amp. Set the meter at 20 ohms.
Last edited by 311ZOSOVHJH at Sep 27, 2009,