#1
I own a mesa f-100 head. I noticed the other day that one of the power tubes is not working. It uses four 6l6 power tubes. The second from the left is not working. So its ON OFF ON ON. I've never had to replace tubes before. But will this hurt my amp continuing to use it this way? Also I believe mesa tubes are a fixed bias so all I have to do is replace the set, which reading around various places are either the 2 end tubes, or the 2 middle tubes, its NOT a left and right set. Is this correct? If so, I would have to replace the 2 middle tubes. Any help would be great. Thanks.
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#2
If you replace power tubes, usually you replace all of them, ie 2 in a 50watt, 4 in a 100watt. You're correct in thinking Mesa's are fixed bias so you MAY be able to just replace the middle pair, but I'd check it out first to make sure that it's safe to do so. Personally, I'd change the lot to be on the safe side & sell the good pair to someone with a 50watt Mesa!
#3
Thanks for the info. But is this hurting anything at all?
Fender American Select Strat HSS Antique Burst
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PRS Custom 24 USA
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#4
It could be hurting your tone. Does your amp crackle? Does it not sound as loud as it used too? Just to speculate here a bit. Your only running at half power right now with a inoperative tube. Which also means your running at half the impedance. So you are probably straining your OT.

You can replace just the 2 tubes. But I don't recommend it TBH. And yes Mesa's are fixed bias. But when you order new tubes they need to be in Mesa's bias range.

I recommend.
www.thetubestore.com
www.dougstubes.com
www.eurotubes.com

They all carry tubes in Mesa's bias range. And they will all answer any questions you may have. My tubes arrived within 24hrs when I last ordered mine. They all carry different brands so choose a site and pick your flavor. If one site doesn't have them go to the other. I don't recommend Mesa tubes they sound like garbage. And are nothing more than relabeled (Insert cheap brand tube here)
If you start a reply with: I have never played one but I have heard good things about it! Your opinion is invalid.
#5
Well no I havent noticed much of anything. I normally dont bring it home with me. I usually leave it at my practice spot, so I only get to hear it twice a week. Im not sure how long its been out. I normally dont look back there for anything. Theres an authorized mesa dealer 3 minutes down the street who sells mesa brand tubes. So I'll stop there if I have to. I did not buy this amp new, I bought it used. So it may have been out since I got it a few months ago. But as I said, I dont get to play it that often.

Obviously I've never switched out tubes before in this amp. But mesa tubes sound bad? Im not even sure if they are mesa tubes inside of it. But Im a total noob when it comes to tubes. I dont know what tubes affect what sound or whatnot. I'll check the tubes tomorrow to see if it says mesa on them somewhere.
Fender American Select Strat HSS Antique Burst
Fender American Select Strat HSS Transparent Crimson
Fender American Deluxe Strat
PRS Custom 24 USA
Gibson Les Paul Standard
Gibson Les Paul Traditional
Ibanez RG1570 Prestige
Parker PDF100