Error in On-Line Setup Chart for TV7-B/U

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Error in On-Line Setup Chart for TV7-B/U

Post by Guest on Wed Oct 08, 2014 11:51 pm

Greetings to the Forum:

I have discovered an error in an on-line setup chart for the TV-7B/U military tube tester.   This setup chart is located at:  http://www.antiqueairwaves.com/nlee/tv-7_index.html

The error is in the selector settings for tube type 7233, which is a lo-mu triode; typical use is as a regulator pass tube in small regulated power supplies.

The published selector settings are:  EV 23080.   If used, this setting results in the short neon being lit in all 5 positions.   Obviously, it would not be safe to proceed with the test with this setting.

There are 4 plate pins in the 7233:   1,3,6 and 9.   Of these, only pin 1 can be used if the shorts test is to be valid and the tube tester operated safely.

Therefore, the correct selector settings in the TV-7B/U for the 7233 are:   EV 21080.

This was discovered by me when using my TV-7B/U, serial 163.   Perhaps later serial numbers are different; however, I believe the design was standardized for production under contract, so this problem may be prevalent.

I hope this is of some use.

Regards,
Jim T.
KB6GM

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Re: Error in On-Line Setup Chart for TV7-B/U

Post by Resistance is Futile on Fri Oct 10, 2014 2:50 am

In my TV-7D/U, ser. No. 1257 (Apointe Industries Inc.),that tube isn't listed?
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Re: Error in On-Line Setup Chart for TV7-B/U

Post by Guest on Fri Oct 10, 2014 7:47 am

Greetings to Resistance is Futile and the Forum:

It is not in the standard setup chart for the TV-7B/U either, but I have made up a supplemental page to the setup book with many of the setups taken from the web site mentioned, including the 7233.

When I tried to use that setup, I got the all shorts issue.   Experimentation with my TV-7 enabled me to figure out how to test the tube.   The bias setting is reasonable; don't know about the range but I am going with it for now.

My Hickok 534 has a listing for the tube, but it checks it for emission only   (Press P3 or Rectifier), as the thing requires about -100 volts to cut it off.   That's beyond the bias capabilities of most tube testers.   Apparently, the TV-7B/U can manage some effect, because when I ran the bias from 90 (specified) all the way up to 100, the GM reading did drop.

As with all tube testers, one needs to take the results with a grain of salt, but one can hopefully get an idea of whether the tube is useable or not.

The same site also has a complete chart for the TV-7D/U (as I recall) but I didn't pay much attention as I don't own one.   The 7233 might be listed there or it might not... since you have one, I'll let you do the research.   ;^)

Incidentally, as you will observe above, I haven't figured out how to embed emoticons yet.

Regards,
Jim T.
KB6GM

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Re: Error in On-Line Setup Chart for TV7-B/U

Post by 75X11 on Tue Oct 14, 2014 6:19 pm

It has been one of my sincere regrets not getting a TV-7 when they became available at the low post cold war prices they once held. It was a trusted friend during my military service.
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Re: Error in On-Line Setup Chart for TV7-B/U

Post by Resistance is Futile on Thu Oct 16, 2014 3:42 am

The rectifiers are outrageously priced, just because that tester is an overrated Icon. That's not saying it not nice, just if you don't have one, your not as in with the in crowd.

Yes I do have that spreadsheet with that tube listed. I don't know that I would need it anyway. (the settings that is) because I think that even has the GM listings for the F switch that are purported to go up to 60,000 Gm. There are no tubes that have anywhere that much gain that I have been told. (so its possible that the last two switches actually read the lower gain.) and only go up to 30,000 Gm.
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Re: Error in On-Line Setup Chart for TV7-B/U

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