Replacing power tubes "on the fly"?

[Inazone]

I've never had a tube go bad on me yet, but if it were to happen, can a bad power tube be replaced with another of the same type (ie. 6L6) without doing anything else? I use 50-watt amps (two 6L6s) and always carry a matched pair for backup, but just wanted to make sure there's nothing additional involved.

[screamindv]

Re: Replacing power tubes \"on the fly\"?

I play Mesa Boogie so no biasing is required. To get through the show, there should be no problem. You shouldhave most amps rebiased when you change power tubes. I hope you carry spare preamp tubes because i have had to change them on the job alot more than poweramp tubes.
Screamin'

[Deneb]

Re: Replacing power tubes \"on the fly\"?

Ina, you could actually find someone to test your tubes, and get the readings from them, and then order a set of tubes, that are rated likewise...and viola, you don't have to worry about it [img]/images/graemlins/smile.gif[/img]

[Twisteramps]

Re: Replacing power tubes \"on the fly\"?

[ QUOTE ]
I play Mesa Boogie so no biasing is required.

[/ QUOTE ]

So says mesa...

you should be ok replacing a bad tube at a show to finish out a gig, but check the bias afterwards.

And mesa is full of shit - their 'no bias needed' circuit is the same as many fixed bias amps. Just another Mesa claim.

Pete

[screamindv]

Re: Replacing power tubes \"on the fly\"?

Twisteramps: Your claim may be true because when I replaced my poweramp tubes at the tubestore, they sent 8 tubes, matched and numbered for my Simul 2:90

[metallicarocks]

Re: Replacing power tubes \"on the fly\"?

[ QUOTE ]
Twisteramps: Your claim may be true because when I replaced my poweramp tubes at the tubestore, they sent 8 tubes, matched and numbered for my Simul 2:90


[/ QUOTE ]

I would believe few others over Pete's word. He builds amps for Christ's sake!

[Deneb]

Re: Replacing power tubes \"on the fly\"?




From their stand point, if you're using their tubes, there is no need to rebias, so they say their tubes are of certain values, making it an okay swap (read the manual). No where do they claim (that I've seen, but I could be wrong) that any tube is meant for their fixed bias amps. They are only implying that their bias is fixed, and if used with tubes of X value (meaning their value) you're fine.

Funny enough, I remember, the first week I had my Mesa, some shit went wrong with it, and the tech said it was something with the cathode biasing.

[Twisteramps]

Re: Replacing power tubes \"on the fly\"?

BTW, you can get tubes from other vendors that are EXACTLY the same tubes minus the mesa screen printing for much cheaper and they can be within Mesa's range.

I had a '68 Fender Princeton Reverb that had the exact same setup mesa uses bias wise - and amps were using that before them. It just means you don't have an adjustment within the amp to set it for the tubes used. There's nothing special about Mesa's setup other than it's cheaper for them to build amps by a tiny amount and it gives them the excuse to claim that only their tubes will work in their amps.

I've also seen mesa state that they will ONLY honor their warranty if you use mesa branded tubes. Of course, this is horsecrap, since every tube mesa sells is made by someone else and rebranded. Mesa just jacks up the price and hopes that you'll be stuck on using their tubes and keeping the cash flow going. I like some of their amps a lot: I just don't like their business practices.

Pete

[Inazone]

Re: Replacing power tubes \"on the fly\"?

The reason that I ask is that when I had my Peavey Classic 212 in the shop a couple years back, I had Ruby 6L6GCs installed simply because I already had some on hand. I have since bought Peavey-branded tubes as well as Sovtek and Ruby, all in pairs. Just trying to cover my bases.

These Peavey amps are very basics - solid state preamp (clean only) and two 6L6s in the power section. Is there any particular reason to change power tubes as long as they continue to function properly?

[toejam]

Re: Replacing power tubes \"on the fly\"?

I replaced the two EL84s and four 12AX7s in my Mesa combo with JJs and EHs and didn't have to rebias.