Output tubes in a Showman

[bluesdoc]

My bandmate has a Showman that usually sounds great but as of last night's rehearsal, has lost all its balls. I thought I'd give some tube swapping a try. Do I switch output tubes in pairs that are the outside/inside (ie, either the two outside or the two inside), or side by side? Thanks.

jon

[Blue Strat]

Since you're about to undertake a complelely random procedure (the way you've framed it), it probably doesn't matter which pair you replace since any one, or more, of the power tubes could be bad.

You could learn something about the power tubes and amp by taking bias measurements (which you should do anyway when replacing tubes).

If nothing else, you can swap one tube at a time. Personally, I'd swap a whole set at once so you know whether the problem is a power tube or not. If that helps, then swap in the old tubes one at a time to figure out which one (or ones) are bad.

[bluesdoc]

Yeah, I'll bring my bias test meter. Thanks Mike.

jon