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Post by pintail78 on Aug 30, 2013 15:12:44 GMT -7
Hey I just changed my power tubes in a 62 vibrolux, they had a solid 12-15 months of gigging on them, they were biased at 43ma, so the amp was right on at 35 watts (about 415 Volts), I put in a new set and man they were all the way up to 68ma! I know the conductance varies on these guys but not by that much.
The other thing I noticed is that when I re biased and let the amp warm up, like 1/2 hour it came up about 4 ma. I know the resistors get more conductive when hot and probably effects the older amps a bit more that seams a bit excessive.
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Post by zpilot on Aug 30, 2013 22:50:45 GMT -7
Groove Tubes used to market a 6V6 type tube that drew considerably more idle current. They called it a GT6V6-HD. They noted on the package that it required an additional -8 volts for proper biasing. If JJ is selling a 6L6 now with a similar requirement they should have given you a heads-up like GT did. Shame on them.
As for the change after warm-up, that's not too unusual.
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Post by pintail78 on Sept 14, 2013 19:53:56 GMT -7
Yes, I particularly notice the increase in ma with the brown fenders and older. Ive found that a goo 20-30 minutes warmup and setting just a bit lower works well. With the JJ's, Ive always really liked their tubes, Ive never had a bad set. This was a bit odd as they pulled almost twice the current as the old ones and even the new set I just got. That much variation seems strange......maybe I should make sure they are 6L6's I have a set of EL-34L laying around.......maybe I'll double check I didnt put them in by mistake!
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Post by pintail78 on Sept 14, 2013 19:54:12 GMT -7
Yes, I particularly notice the increase in ma with the brown fenders and older. Ive found that a goo 20-30 minutes warmup and setting just a bit lower works well. With the JJ's, Ive always really liked their tubes, Ive never had a bad set. This was a bit odd as they pulled almost twice the current as the old ones and even the new set I just got. That much variation seems strange......maybe I should make sure they are 6L6's I have a set of EL-34L laying around.......maybe I'll double check I didnt put them in by mistake!
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