Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => AmpTools/Tech Tips => Topic started by: Beezerboy on February 06, 2021, 05:41:04 pm
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Any body own one or have testing data? I got one a while back and tried it out on some known good tubes & it works, though it gets different readings than my Precision 912 (totally different machines). The problem with the TV4 is it has no testing data for the 6BQ5/EL84 (whuuuuuuuuuuuuuuuut? yeah, I know). I've been all over the web looking and come up blank, so if anybody has data that would be great. Also, is there a cross over number for a military VT? Again, I've looked. As a last ditch effort, if you have experience with this tester, maybe you can make a recommendation on settings.
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I can't help you for your TV4A , I'll ask at this forum ; https://antiqueradios.com/forums/viewtopic.php?f=8&t=324638
Looking with Google , I found a chart for your Precision
http://web.archive.org/web/20090206020326/http://oldradios.50webs.com/precision/900/P900_series.pdf
From Antique Radios : https://www.antiqueradios.com/forums/viewtopic.php?f=8&t=200728
Good luck .
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Weston. Not Westinghouse.
Apparently this series, even into the TV7 model, had trouble with 6BQ5/EL84.
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'doh.... yeah Weston. workin from memory & proving I don't have one.
it's kinda a neat tester & looks near like new inside the case. seems to work well on the 12a()7 and other tubes I've tried on it. it finds the weak or failed ones. they way they list the settings seems to reverse the A and B side triodes (which side is under test) but I still get useable information.
thanks guys....
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TV4 was introduced in 1954.
EL84 was introduced in 1954.
You see the problem. Ideally there would be a 2nd edition data-table with EL84 test. But looking for such a thing I keep finding clues that the TV4 does not like the EL84 pin-out, reporting it full of shorts. Which may be a false negative, but if it isn't the TV4 apparently can burn-up in minutes. And Weston my have only mild interest in supporting the TV4, because new tubes all the time (1950s) and opportunity to develop and $ell a TV7 tester.
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Even the manufacturers could not agree on a standard pin out for EL84/6BQ5!
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riddle me this then.... I have a pair of Telefunkin EL84s that test shorted on my Prescision 912 (which is at prolly 10 years older than the Weston) yet they work fine in the Telefunkin radio I'm restoring. this is a long/short wave and AM/FM band receiver. not all the bands were working, I suspect because there are other tubes that are definitely bad (failed on both testers). the FM comes in beautiful. I didn't run it long because guys on the radio forums tell me the selenium rectifier should be replaced first.
anyway, back to the tubes... originals from 1954. is this a different pinout???
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:dontknow:
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riddle me this then.... I have a pair of Telefunkin EL84s that test shorted on my Prescision 912 (which is at prolly 10 years older than the Weston) yet they work fine in the Telefunkin radio I'm restoring. ...
The data Latole found, and PRR's post both told you this tester would report a good EL84 as having shorts. You overcome that problem with a different tube tester. Or by ignoring the Shorts test for that tube cause you can't trust it.
... back to the tubes... originals from 1954. is this a different pinout???
Have maybe 80-100 old American & European EL84/6BQ5/7189 tubes. Staying within a single manufacturer, tubes varied as to whether or not the "no connection" pins (1 & 8) were or were not connected to some other element within the tube. Or if not connected, they may have had overly-long pin-stubs inside the glass that were very close to some other element in the tube.
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sorry so late getting back but the answer is yes, the internal arrangement is different. the unused pins are tied to some of the other pins inside, apparently for a stronger support for the plates. so yes, I read a short across pins that are open in a modern production tube. you can read them with an ohm meter since its a dead short.
I ran down the schematic of my Precision 912 & traced the path through the selectors and thats why it will read a short on some settings a newer tube won't. I know to just ignore the reading as a false positive. BUT... if you have the socket wire up using contact pins 1 or 6 for resistors etc.... that's gonna be a bad thing.
btw, I'm using these in a 50's Telefunken radio I restored. I believe they are original to the rig. they sound great