KT-90 question

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In my Dyna MK3 Clone amps that have individually adjustable bias, I find that the KT-90 tubes I have need to be re-adjusted every time the amps are turned-on after being off for more than 1 hour.
In both amps the RHS tube consumes more current than the LHS tube. After a series of adjustments to the Bias controls I can key them in between 55 and 60 ma with 485 Volts on the plates. A few more adjustments later any they remain spot-on for the rest of the evening.
Wondeful lush sound, but it's annoying that I have to re-bias these tubes every time I turn on my amps.
I tried to leave the bias control's alone to see if it was a warm-up issue, but the RHS tubes climbed up to 80 ma while the LHS tubes stayed at 55 ma.
Any ideas what may be going-on? The output transformer has a 4300 Ohm Primary and the tubes are operated in an Ultra-Linear configuration.

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Kimber Kable

Topic - KT-90 question - shermanr@prw.net 11:13:52 04/17/06 (6)

Re: KT-90 question - Bob Samuelson 12:15:08 04/17/06 (5)

Re: KT-90 question - bluelobster 17:47:59 04/17/06 (4)

Re: KT-90 question - Bob Samuelson 19:41:58 04/17/06 (3)

Re: KT-90 question - shermanr@prw.net 06:45:51 04/18/06 (2)

-. --- - .... .- -. -.- ... - Bob Samuelson 17:19:06 04/18/06 (1)

Watch your language Bob....... - bluelobster 18:57:02 04/18/06 (0)

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