#1
I had bought a used blockletter 5150 a few months ago and had played a few shows with it, and I was really loving how it sounded. However, during the past few practices, I noticed that the volume would keep leveling off and the gain would kind of back off randomly while I was playing. Is this an indication that I should invest in some new tubes? This is my first amp with tubes in it so I don't know if I can replace them myself or if theres more involved and I should take it to a tech or something. Any info or suggestions are appreciated thanks!
#2
Yes you can replace them yourself and it does sound tube related

Pull the tubes straight out of the socket. You may have to wiggle them a little.

The power tubes don't have to be biased, there really isn't much adjustment available anyways.
2002 PRS CE22
2013 G&L ASAT Deluxe
2009 Epiphone G-400 (SH-4)
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Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
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MXR Smart Gate
#3
Sounds a lot like my used 5150 212. Time for new tubes.
Ibanez Prestige RG852MPB
Ibanez Prestige RG652KFX
ESP E-II M-1
LTD AW-7
Schecter Loomis NT
EVH 5150 III 50
PRS 212 DB
Line 6 POD HD500X
Deadhorse OD/Boss HM-2
#4
Buy a set for the sound you want i.e. you can have more gain or headroom and buy the outputs as a matched set whether it's duo or a quad, they're already matched in their values so don't need any biasing.

I just got a quad set of the JJ power valves from hot rox and they sound great, really transformed the amp.
#5
From what I recall, 5150s came biased cold from the factory, so you can get away with just dropping a set of 4 in there without biasing. However, if the amp has ever been re-biased previously, then it would be worth it to bring it to a tech and make sure that everything is ok with the new tubes.
#6
The Peavey 5150s can't be biased without a modification. They probably don't need to worry about that.
Ibanez Prestige RG852MPB
Ibanez Prestige RG652KFX
ESP E-II M-1
LTD AW-7
Schecter Loomis NT
EVH 5150 III 50
PRS 212 DB
Line 6 POD HD500X
Deadhorse OD/Boss HM-2