Members waveman Posted January 29, 2007 Members Share Posted January 29, 2007 Ok, here is what happened, I bought some Sylvania 6L6 GC power tubes for my peavey ultra 60. It started making a popping sound and then blew a fuse. So I put a new fuse in the amp and start playing with it again...starts popping again. So I put the old power tubes back in after shutting the amp down and turning it back on a couple of time to see if it kept popping. The popping went away, so did I get bad power tubes or could there have been a biasing issue? The ad on ebay said the tubes were matched and tested better than new. Link to comment Share on other sites More sharing options...
Members L6Sguy Posted January 29, 2007 Members Share Posted January 29, 2007 did you bias upon putting in new tubes? or have you just been swapping tubes back and forth? and more importantly, is this particular amp designed to be able to do that? Link to comment Share on other sites More sharing options...
Members waveman Posted January 29, 2007 Author Members Share Posted January 29, 2007 did you bias upon putting in new tubes? or have you just been swapping tubes back and forth?and more importantly, is this particular amp designed to be able to do that? It's a Peavey Ultra, so it's a fixed bias...And the amp is supposed to 6L6 GC power tubes, and that's what I bought. Link to comment Share on other sites More sharing options...
Members erksin Posted January 29, 2007 Members Share Posted January 29, 2007 Fixed bias isn't the same as Cathode bias - if you're gonna swap tunes, you'll have to rebias everytime. Most BF/SF Fenders are fixed bias too, FWIW... Link to comment Share on other sites More sharing options...
Members waveman Posted January 29, 2007 Author Members Share Posted January 29, 2007 Fixed bias isn't the same as Cathode bias - if you're gonna swap tunes, you'll have to rebias everytime. Most BF/SF Fenders are fixed bias too, FWIW... Ok, so would that cause the issue that I described then? Blowing a fuse and popping sounds coming from my within 5-10 minutes of warming up? Link to comment Share on other sites More sharing options...
Members erksin Posted January 29, 2007 Members Share Posted January 29, 2007 Ok, so would that cause the issue that I described then? Blowing a fuse and popping sounds coming from my within 5-10 minutes of warming up? Potentially - have you tried it with the old tubes? Link to comment Share on other sites More sharing options...
Members BIG TIM Posted January 29, 2007 Members Share Posted January 29, 2007 So I put the old power tubes back in after shutting the amp down and turning it back on a couple of time to see if it kept popping. The popping went away, so did I get bad power tubes or could there have been a biasing issue? The ad on ebay said the tubes were matched and tested better than new.Ya he did... Link to comment Share on other sites More sharing options...
Members waveman Posted January 29, 2007 Author Members Share Posted January 29, 2007 Bump since I have filed a paypal dispute, and want to make sure I am not off base by doing so... Link to comment Share on other sites More sharing options...
Members erksin Posted January 29, 2007 Members Share Posted January 29, 2007 Bump since I have filed a paypal dispute, and want to make sure I am not off base by doing so... Personally, I don't think you have a claim. You dropped a set of tubes into an amp and ran it without biasing them properly. The seller can't help that. Before you do anything, I'd take them to a tech with a good tube tester and have them tested. Of course, you could have ruined them by doing what you did - but maybe the tech could find something different that wasn't your fault. This is one of those 'live and learn' type deals if you ask me - you'll know better next time. Link to comment Share on other sites More sharing options...
Members gringo699c Posted January 29, 2007 Members Share Posted January 29, 2007 Fixed bias isn't the same as Cathode bias - if you're gonna swap tunes, you'll have to rebias everytime. Most BF/SF Fenders are fixed bias too, FWIW... You cant rebias the peavey amp im pretty sure. They take what ever tubes they take and the bias is set and cant be changed. That is why places like fjamods.com mod the amp so you can change the bias to your liking If your amp takes 6l6's, you can change the 6l6 tubes anytime and not rebias. Chances are the tube has leakage or a short. Of course the only way to be sure is to test the tubes on a tester. You can pick up and ok tester off ebay for $50-100 Yard sales and estate sales are a good place to get one. I got a nice heathkit tube tester last week for $10 at an estate sale. Good luck. Link to comment Share on other sites More sharing options...
Members erksin Posted January 29, 2007 Members Share Posted January 29, 2007 You cant rebias the peavey amp im pretty sure. They take what ever tubes they take and the bias is set and cant be changed. That is why places like fjamods.com mod the amp so you can change the bias to your liking If your amp takes 6l6's, you can change the 6l6 tubes anytime and not rebias. Chances are the tube has leakage or a short. Of course the only way to be sure is to test the tubes on a tester. You can pick up and ok tester off ebay for $50-100 Yard sales and estate sales are a good place to get one. I got a nice heathkit tube tester last week for $10 at an estate sale. Good luck. You can bias a fixed bias amp - I'm not intimately familiar with the Peavey, but I can't imagine why you couldn't bias it, there'd be no way to change tubes when the time came. I'm not a tech by any means, but I do know that in biasing a fixed bias amp there is some calculation they do to determine the proper resistor or cap to use to set the bias. It's how it's done on BF and SF Fenders and the like. Link to comment Share on other sites More sharing options...
Members gringo699c Posted January 30, 2007 Members Share Posted January 30, 2007 You can bias a fixed bias amp - I'm not intimately familiar with the Peavey, but I can't imagine why you couldn't bias it, there'd be no way to change tubes when the time came. I'm not a tech by any means, but I do know that in biasing a fixed bias amp there is some calculation they do to determine the proper resistor or cap to use to set the bias. It's how it's done on BF and SF Fenders and the like. I see what your saying. Yes you can change the caps and resistors to change the bias but your average person player couldnt pull this off. The hole idea of the fixed bias amp is so the average person can put in the same type of tubes and not worry about rebiasing the amp. Personally I think there was something wrong with one of the tubes. doug at www.dougstubes.com will test tubes for ya for free is you pay the postage. Just call him. He nice as hell and knows alot about tubes and has several hi-end testers.Chris Link to comment Share on other sites More sharing options...
Members HKSblade1 Posted January 31, 2007 Members Share Posted January 31, 2007 ask the seller for a new set of tubes. If their customer svc is a problem go through a claim. Were they delivered by UPS? I received a box of glass from Tubesandmore that was a UPS ship! They sent a new set and settled with UPS. That was better than expected Link to comment Share on other sites More sharing options...
Members waveman Posted January 31, 2007 Author Members Share Posted January 31, 2007 Well after all was said and done. I am convinced that at least one of the tubes was bad. I have put several hours on this amp since Sunday with my old tubes with no issue. I also contacted Peavey support, posted this at TGP Amp Tech Info forum, and did a little more research. The concensus was there is at least one bad tube out of the pair. In fact, one guy at TGP and another on the Peavey forum hit the nail on the head I think...tubes can test fine with standard tube tester, but that doesn't mean they don't have shorts or other internal issues that don't come to light unless the tube is put under a high current condition, like a guitar amp. The happy ending is the seller understands that old tubes can be flakey, and he is refunding my my money:thu: Just for the hell of it, I bought some cheap $10 chinese 6L6 GC's to see how they work...but I won't be bitching if they don't for that much $$$. The Sylvania's cost me quite a bit more. I will be buying new JJ's in the future I guess. Anybody know of a new production 6L6 that have that vintage mid tweedy push to them? Link to comment Share on other sites More sharing options...
Members BillM Posted January 31, 2007 Members Share Posted January 31, 2007 you can't bias a fixed bias amp without doing some kind of mod to the amp, such as Bill's blues jr mods. i'm not familiar with peavey, i would check to see what the bias for these amps is, if it's to high it will definately toast your tubes, or go through them in no time. (is this some sort of conspiracy :-)) i've had good luck with the tubestore, ..... you can get matched pair from them ....as long as you don't mind doing business with canuckies. just guessing, i would say the screen is hosed on the tube. Link to comment Share on other sites More sharing options...
Members HKSblade1 Posted January 31, 2007 Members Share Posted January 31, 2007 JJ's or Svetlana pref JJ's why? less microphonic and hold up wellNOS can get pricey Link to comment Share on other sites More sharing options...
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