Testing 6L6 on Hickok 539C

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lostcauses10x
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Feb Mon 25, 2013 2:39 am
Truth or Cosequences, NM

Re: Testing 6L6 on Hickok 539C

Post by lostcauses10x »

Bluetrain1950 wrote:I have the 539B and 539C and TV-7DU but my go to tester is my Fender Amp !!!!!!!!!!
Testers are good at the go, no go, but in circuit is always the true test.

Testers also good to see if pair for push pull are reasonable close..yet again not sure until trying em
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westcoastjohn
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Dec Sat 24, 2011 8:17 pm
Qualicum Beach, Canada

Re: Testing 6L6 on Hickok 539C

Post by westcoastjohn »

Bluetrain1950 wrote:I have the 539B and 539C and TV-7DU but my go to tester is my Fender Amp !!!!!!!!!!
Thanks for posting, and I have a question. Do you want your 6L6's matched and if so by what method?
Or do you like them mismatched for a more authentic blues tone? No joke, I'm curious. I can't hear well enough myself to discern much of this type of thing.

I have matched tubes in amps by comparing cathode current, but wonder how that works with a pair of tubes that was matched on a tester. Imbalance in the output transformer windings makes a difference, no? or maybe not?
Last edited by westcoastjohn on Nov Sat 25, 2023 6:37 pm, edited 1 time in total.
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Barry H Bennett
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Nov Wed 30, 2016 6:35 pm
Sunbury, Ohio 43074
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Re: Testing 6L6 on Hickok 539C

Post by Barry H Bennett »

A tube tester cannot 'match' tubes. The best a tube tester can do is match tubes at only one point on their operating curve, which may get you in the ballpark but is hardly a match.

To MATCH tubes, requires either a curve tracer, or a bench full of instruments, some graph paper, and lots of time and patience. I vote for the curve tracer :)

Truly matched tubes will have the same characteristics at every point along the linear portion of their operating curve, and even better, the non linear parts.

SO ..... that's the limitation of a tube tester for matching :mrgreen:
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westcoastjohn
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Dec Sat 24, 2011 8:17 pm
Qualicum Beach, Canada

Re: Testing 6L6 on Hickok 539C

Post by westcoastjohn »

Thanks, Barry. I wonder how a perfectly matched pair can perform perfectly when the output transformer is bound to have mismatched secondaries?
At least with a slightly mismatched pair, you can swap them into opposite sockets to get them closer to even. :D
Read the War Diaries: A Radio Amateur in Kyiv, Stalemate by Volodymyr Gurtovy
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Barry H Bennett
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Nov Wed 30, 2016 6:35 pm
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Re: Testing 6L6 on Hickok 539C

Post by Barry H Bennett »

Well, of course matching tubes has nothing to do with matching the rest of the circuit. But I think you rapidly get into a law of diminishing returns here. What exactly are you going to hear as a difference?

And at what power levels. And in what room or listening environment?
Preserving the hist. of electronics, one boat anchor at a time! :)
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ampstamp88
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Apr Sat 04, 2015 5:15 am
Willits, CA.

Re: Testing 6L6 on Hickok 539C

Post by ampstamp88 »

I've come to the conclusion that the Wizard of Oz has more to do with reality
than tube tester tube matching activities.
"How come we never watch Television?" - sonuva TV repairman in the fifties, Mac Rebennack.
Chris108
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Jun Fri 19, 2009 5:34 pm
Floral Park, New York

Re: Testing 6L6 on Hickok 539C

Post by Chris108 »

Matching tubes on a tube tester is not such a bad idea for circuits where it matters. Just try and set the DC balance and calibration on a VTVM, when the 12AU7 in the balanced bridge circuit has wildly different transconductance readings from one section to the other. In audio I begin to hear the difference when the output tubes test more than about 10% different--and that's on a plain emission tester, not some big fancy Hickok that takes up half the workbench. My hearing isn't even all that good anymore, having lost some of it to an inner ear infection about 20 years ago.

The thing I never really understood is, why all the fascination with calibrating tube testers, sending them to gurus for alignments only they and nobody else--not even Robert C. Hickok himself, if he was still alive, could perform, magical oracle of Delphi bogey tubes, and all the rest? Yes everything in a balanced amplifier stage has to be matched, otherwise there is little point in worrying about the tubes. But when you consider that the finest speakers available add a percent or two distortion, the output transformer adds distortion, the vinyl LP, FM tuner, or DAC in the CD player are adding distortion, and every other stage and circuit in the amplifier is adding distortion, then what does chasing down that last uMho on an old Hickok really accomplish? Without knowledge of a tube's plate resistance, which is subject to manufacturing tolerances and varies from one tube to the next, uMhos can't even tell you exactly how much gain a particular tube is theoretically capable of.
"Hell, there are no rules here--we're trying to accomplish something!"

Thomas A. Edison
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