Amp Advice - Is this a tube problem, or something else? Help!

NBGuitar

So the other day I was playing through my Blackstar HT-40 when my guitar sound cut out and there was just a very loud wailing (louder than what I was previously playing). Then after I turned it off there was still some crackling coming from the speaker. I've tried the amp a few times since and it seems to be back to normal, although there is now a click from the speaker every time I turn the amp off (never happened before). Does this sound like a blown tube, or is it something else? If it's not tube I had a recent service that should cover repairs, otherwise I need to get a rebias and everything done.

Thanks in advance for any light you could shed on the situation!

Budwiser

Some many offer advice for troubleshooting amps..so before grabbing the tool box and looking in side the amp..have you done any service work before on amps? there's plenty of volts in there to zap wondering hands..

Quick checks such as tapping the valves lightly with a pencil to see if there's any flashing going on inside the power and pre-amp tubes.

Plate load resistors can go high or go open circuits..if unsure pop it a long to the local tech.

ICBM

I was hoping Dave ( @ecc83 ) would comment since there may be some 'known issue' I'm unaware of that's not valve-related and would do this, but otherwise it does sound like a valve problem, preamp rather than power amp.