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Peter, as Rob mentioned: if you are getting adequate output, I would leave the tubes you have in the rig.? Keep others for spares.

IMO, the concept of having "matched" 6JB6's is overrated.? Given tolerances for other parts in the circuits, you can have one tube doing more "work" than the others, regardless of their DC characteristics.? The important thing to remember is not to overdrive them to try and eke out every last milliwatt from the set. (You'd be surprised how many people do this!).

A TR3/4 is capable of 200W output on 80 and 40 and new tubes can also do this on 20 but you're starting to push them.? 150W out on 15 and 10 is absolutely grand.??

Yes, I've been able to get 200W out on 15m with a fresh set but I throttle back on mine to about 140-150 on 10, going to about 180-200W on 80.? By keeping them below their absolute max, it doesn't matter if one tube is pulling more than the others because they're all within their plate dissipation ratings.? Those are 17.5W per tube in CCS -- you can run more than that in ordinary CW or SSB.

Having said all of the above, it's wise to use tubes that are the same brand or at least of the same mechanical design (it's easy to discern the two types from looking at the top of the frame inside) and within 20% of each other.

Steve Wedge, W1ES/4

Time flies like an arrow.? Fruit flies like a banana.

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On Sunday, March 24th, 2024 at 9:43 AM, Peter A <christinepeterarsenault@...> wrote:

My Drake TR4cw/rit is going in tomorrow to a very experienced tech for a bit of servicing.? If needed, he'll be doing
an alignment for me.? All three of the 6JB6's presently in the rig are the green label Sylvania possibly originals, or at least were replaced
with the manual's recommended Sylvania tubes at one time?? All three are fairly close to 90% or a bit over on my Jackson 658-1 tube tester. I have a selection of 6JB6 tubes, which include anything from Raytheon, RCA, GE, Marconi, Westinghouse, but not another "matched" set of three of any specific brand.? I can match two, but not three.? I do have some that test at 107% +or- and would be able to put three tubes together that test around this 107%.
Do the three 90% green label Sylvania's stay in place or would three of the "stronger" non matching brand tubes, but are heathier at 107% +or- be better, or is it completely unacceptable to install different brand tubes for this purpose.
I was planning on bringing these extra 6JB6's with me tomorrow and asking the tech what he think about it, but
would love to hear what you think of this.? My take on it is you don't mix and match here and therefore leave the Sylvania's in.
Thanks,
Peter
VE9KX
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