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Any guesses on this tube
Any guesses on this tube
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Old 22nd May 2017, 11:42 PM   #1
rsumperl is offline rsumperl  United States
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Default Any guesses on this tube

Good evening everyone,
Well, yet another impulse buy, got these for $10 for the pair on that most famous auction site. My first thought is they are 8236s, but hey I don't know. Do the numbers on the base tell us anything???


Thanks
Ray
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Old 23rd May 2017, 12:33 AM   #2
TheGimp is offline TheGimp  United States
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6146.
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Old 23rd May 2017, 01:11 AM   #3
smoking-amp is offline smoking-amp  United States
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If you can figure out the pin-out, that would narrow it down considerably. Then measure the heater current at 6.3 V (assuming that lights it up properly).
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Old 23rd May 2017, 01:27 AM   #4
TheGimp is offline TheGimp  United States
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He asked for a guess, not a logical analysis.

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Old 23rd May 2017, 01:38 AM   #5
smoking-amp is offline smoking-amp  United States
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WE could do a process of elimination...

It's NOT a 12AX7. Your turn....

Last edited by smoking-amp; 23rd May 2017 at 01:42 AM.
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Old 23rd May 2017, 01:49 AM   #6
Shef is offline Shef
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Hm... not a KT-88 either... next one?
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Old 23rd May 2017, 01:58 AM   #7
TheGimp is offline TheGimp  United States
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Not a 6P41S either.

One of those weird triodes with the grid on top?
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Old 23rd May 2017, 02:05 AM   #8
smoking-amp is offline smoking-amp  United States
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We are left with the hammer option. Or destructive testing. (where's Tubelab)
Triode or Pentode?
How many Watts will it take before bursting into flames?

Time to call in the experts:
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Old 23rd May 2017, 02:15 AM   #9
TonyTecson is offline TonyTecson  Philippines
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Any guesses on this tube
it is octal so 7403, or 3d21wb
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Old 23rd May 2017, 02:29 AM   #10
Tubelab_com is offline Tubelab_com  United States
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Quote:
Or destructive testing. (where's Tubelab)
I have been known to "test" mystery tubes.....usually not destructively. I prefer the term "boundary testing." I find the glow point and back up a bit. Before any testing can be done, the pinout must be determined. The plate is obvious, and the heater should be fairly easy to figure out. The rest should be possible with careful examination.

7403 has an odd pinout, but an easy test. Heater is on pins 1 and 2. Tung Sol did make them, and the square plate looks about right.

The OP had previously stated that he had some 7403's, so some comparisons should be in order.
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