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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Tue 06, 2018 12:30 pm 
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Posts: 2571
Location: Sunbury, Ohio 43074
Quote:
A properly made bogey tube should read the same on any tester, as long as:

1> The plate, grid bias, screen, suppressor, etc. DC voltages are the same as those used in setting up the bogey.

2> The AC grid signal is small enough to avoid over-driving the tube.

The list of "what if's" above is actually at the core of the problem. But before I address that, how does one create a "properly made bogey tube" in this day and age? Unless created by a true magician with tubes and lab grade equipment, I doubt any two bogey tubes would even match each other. And even if one were to do so, somehow, what guarantees that this TUBE is going to maintain it's supposedly precise characteristics indefinitely?

Bogey tubes were never intended to be used across multiple models from multiple manufacturers. To expect this tube to produce similar results on any but the make and model tester for which it was created, is expecting the impossible. There are, simply stated, far too many variables from tester to tester, in the real world, to expect otherwise. It will read differently from one make to the other, one model to the other. Remember that tube testers were, and are, not precision instruments, and were never intended to be. Can you get a bogey, or for that matter any given tube, to act as a reference for YOUR tester? Probably, once you are convinced that your tester is calibrated properly in the first place. At that time, the bogey tube can serve as a check on accuracy over time. Even at that, you'd probably need more than one "type" of bogey tube to really know that your particular tester is staying in calibration for all cases.

Can a bogey tube be used from one make to another? Sure, and it will tell you if your tester is working or not, and even if it is reasonably accurate or not. But for precise readings, across different makes and models, it is in my opinion impossible.

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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Tue 06, 2018 1:59 pm 
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Location: Columbus Ohio
AA6U wrote:
Also, glue_ru's comment that some tube testers like the 533A, etc. have a reject point of 5000 for the 6L6 is not correct.


it is true, that is THE number printed on Hickok's roll, whether it means min, max, reject, desired is another debate.

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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Tue 06, 2018 3:00 pm 
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Barry - thanks for the work on CAD. One of these days, I want to do a mathematical treatment of the Hickok method of Gm measurement. I'll definitely need more time and perhaps more brains; I'm sure better men than I have tried.


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Tue 06, 2018 4:43 pm 
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Joined: Mar Thu 06, 2014 6:01 pm
Posts: 129
Markd,

Speaking as one who has already done it, I can tell you that a) It's not all that difficult and b) you will probably gain some unexpected insights, at least that's what happened to me. If you do, I would love to compare results. They should be the same, but IF not, there could be some interesting things to be learned. I used Multisim 7, a Spice based simulator with fairly poor computation abilities, but a pretty good circuit drawing interface.

Barry's most recent comments about calibration tubes were exactly correct. "I couldn't have put it better myself."

By the way, for anyone who is interested, I have (finally) completed work on the 539B/C calibration box and have it written up along with the circuit schematic as well as a revised work up on the best 83 tube Solid State replacement. Both files are small enough that I could email them as they aren't available on any web site as of now.

The calibration box obviates the need for a calibration tube, does not involve an extensive set up, keeps all dangerous voltages within the box, checks all six ranges with only one switch, and doesn't drift or age like a calibration tube. The circuit is extremely simple and doesn't require expensive parts.

I am now working on revising the 539B/C calibration procedure to make it simpler, and easier for folks without an extensive E.E. background. (It's a pretty big job and it's going to take a while.)

Regards,

Mike


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Tue 06, 2018 5:36 pm 
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Joined: Sep Tue 22, 2009 3:26 am
Posts: 74
Location: Riverside, CA
Mike- You are a saint. I would love to see your final circuit. Ditto on kudos on the calibration tube analysis.

I am constantly faced with people who want their testers calibrated and they most often are lower-end Hickok or emissions testers (no real calibration possible for them except for line set). The Hickok testers that use the shunt control to set GM and 'English' are almost impossible to get right because when you set them to read approximately correct GM, the English is then incorrect. None of the red GM dots on the shunt controls are correct anymore and the shut pots are never linear so a small change on the dial can make a big change in the reading. Plus if you throw in some minor oxidation in the sealed pots, you have a bit of a challenge...

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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Tue 06, 2018 6:19 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 589
Location: Stafford, Texas USA
The Math is here

https://patentimages.storage.googleapis ... 999858.pdf

Best that they could do in 1934-35, a better tube tester can be build today.

Jimmie Stewart


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Tue 06, 2018 6:42 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 2571
Location: Sunbury, Ohio 43074
Hey Mike. Once I ship this project, I am going to turn my attention to a completely new CAD drawing for the 539B. It will eventually be posted on my under construction website/museum, but I will put sections of it up here as i get them done. My intent is to demystify and simplify as much as possible, for those that want to use these antiques, and do not have extensive experience or knowledge.

I wlll also finish up the Hickok 580 re-schematic, which is quite close to completion. As I've noted before, Hickok and several other tube tester manufacturers seem to have deliberately hired only draftsmen who were skilled in obfuscation and mysteriously disappearing lines. My intent is to unwind the mysterious schematics, both for myself and for anyone else interested.

Hopefully, yet this summer

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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Tue 06, 2018 6:48 pm 
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Joined: Sep Tue 22, 2009 3:26 am
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Location: Riverside, CA
Will your 580 schematic contain the necessary "fixes"?

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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Tue 06, 2018 7:09 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 2571
Location: Sunbury, Ohio 43074
Quote:
Will your 580 schematic contain the necessary "fixes"?

If I ever get around to restoring them, yes. In the meantime, if anyone wants to send me "the fixes" I can certainly incorporate them into my drawings. I simply have not gotten that far yet. It took literally half the winter on and off to decipher the original Hickok drawings and verify by comparing it to the actual wiring in my two, which of course, are not identical lol. I am not saying they are complete, nor checked yet, either. Baby steps.

But it seems there is much more need for the 539B/C, so I thought I'd restore mine and fully document that one at the same time.

Any help is always welcome, as long as it does not come with any time demands. 8)
Barry

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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Tue 06, 2018 9:31 pm 
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Joined: Dec Mon 05, 2011 1:10 am
Posts: 313
MarkD wrote:
Barry - thanks for the work on CAD. One of these days, I want to do a mathematical treatment of the Hickok method of Gm measurement. I'll definitely need more time and perhaps more brains; I'm sure better men than I have tried.


The fundamental problem with any such mathematical analysis is that the meter is trying to respond to a train of nonlinear positive and negative-going pulses (only APPROXIMATELY half sine-wave arcs) and electro-mechanically "integrate" them into a meaningful approximation of the "true" mutual conductance of the tube being tested. MISSION IMPOSSIBLE!

If you want a true measure of Gm, then you really should MEASURE Gm, NOT some non-linearly related artificial construct. The way I know best how to do this is using a null-balance bridge circuit ... beside the tube, only completely passive precision resistors (and maybe a neutralizing capacitor to null out inter-electrode capacitance of the tube).

Once you get such a system set up, you can "roll your own" bogey tubes at will and use them to "calibrate" your Hickok circuit tester. BUT, a Hickok-oid tester calibrated to read right on one bogey can NOT be expected to read accurately on other tubes, especially those with substantially different gain, plate current, etc. To measure Gm accurately on a Hickok, you dang near need a bridge-measured bogey tube for every type (or at least every type class) of tube you intend to test.

Of course, WHY you need to know Gm accurately is another question, but IF you feel the need, then do yourself a favor and get (or build) yourself a bridge, and do it right. Quit trying to tease quantitative Gm values out of meter readings on a 539, TV-7, etc. ... just go with the published minimum acceptable reading (or not) and leave it at that. If you are trying to "match" pairs or quads, then getting similar readings for each tube is about as much as you can expect (though Gm matching is only a rather crude way of selecting pairs, anyway).


^^;;^^


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Tue 06, 2018 9:54 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
Quote:
If you are trying to "match" pairs or quads, then getting similar readings for each tube is about as much as you can expect (though Gm matching is only a rather crude way of selecting pairs, anyway).

Two words: Curve Tracer :-D

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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Tue 06, 2018 10:26 pm 
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Joined: Mar Thu 06, 2014 6:01 pm
Posts: 129
AA6U,

Thanks for the kind remarks. If you will send me your email address, I will be happy to send both articles to you. If you spot any errors, please let me know, as I have been known to make mistakes. My address is "m_higgins@charter.net"



Jimmie Stewart,

Thanks for the patent reference. It makes interesting reading. I am not an an attorney, but my understanding is that a patent application doesn't have to have the correct explanation to be valid, which is good thing for Mr. Barnhart, as the analysis on his patent application was seriously flawed. His circuit looks like a Wheatstone bridge, but in a Wheatstone bridge, current flows SIMULTANEOUSLY in both legs, whereas in his circuit it flows ALTERNATELY in each leg. His analysis also makes the tacit assumption that the current is constant in each half cycle, whereas it actually is a half sine wave. There are some other things, but that should give the flavor of the thing!.

The 539 uses a 100 mf. capacitor across the meter which is so much greater than the inductance of the meter that it can be ignored, but when I started looking at this a couple of years back, the math was still so "hairball" that I ended up making a few gross assumptions to make the math half way tractable. I was very pleased when the answer was within 500% of the measurements.



Morcegao,

Your comments came in while I was writing this. I also had the same doubts about the possible non-linearity of the Hickok circuit, and I have a project in mind and partway completed to empirically test this, but based on VERY preliminary results, it may just turn out that the Hickok circuit, when accurately implemented, may just be accurate after all. I have several other projects ahead of this one, but when I can get to it, I will "publish" it here.

Regards to all,

Mike


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Wed 07, 2018 12:14 am 
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Joined: Apr Wed 13, 2016 1:23 am
Posts: 112
Location: Independence, MO
Mr. Higgins,
Quote:
Mike- You are a saint. I would love to see your final circuit. Ditto on kudos on the calibration tube analysis.
I too, would like your latest documentation. Please, E-Mail rja2907@comcast.net.

Thank you in advance for all your help.

Jim


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Wed 07, 2018 1:05 am 
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Joined: Sep Tue 22, 2009 3:26 am
Posts: 74
Location: Riverside, CA
Thanks! My email address is aa6u@arrl.net

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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Wed 07, 2018 2:51 am 
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Joined: Mar Thu 06, 2014 6:01 pm
Posts: 129
Jim, Scott, and Bill;

You should have the two newest essays. If not please let me know. If you spot any mistakes also please let me know so I can correct them.

Thanks,

Mike


Barry,

Nice to hear from you. If you would like copies also, just let me know. I would like to see your drawings when you get them done, especially for the circuitry around the shorts switch as there are so many mistakes in that area in the Hickok schematic that I gave up on it and probably will never get back to it.

Regards,

Mike


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Wed 07, 2018 4:00 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1181
Location: Tucson AZ
Thank you Mike for your work and sharing it!


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Wed 07, 2018 4:01 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1181
Location: Tucson AZ
Thank you Mike for your work and sharing it!


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Wed 07, 2018 9:05 am 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 2571
Location: Sunbury, Ohio 43074
Thanks Mike. Yes, I'd like a copy as well please. As to the shorts test area of the schematic, is this for the 539 or the 580? Either way, I hope to get back to this documentation project sometime next week or so once my current "real job" project rolls out and I get a slight breather. The 580 is nearly done drawings wise, I just need to do a verification one last time against actual wiring, and then split it up so I can post it here (file is too large) or get my website up and running.

If you refer to the 539, I have not yet started documenting that one yet, but perhaps I'll do it first. I want to get mine restored anyway.

Let me know, and good to hear from you again
Barry

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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Wed 07, 2018 4:28 pm 
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Joined: Aug Wed 31, 2011 11:23 pm
Posts: 450
Location: Tucson, AZ
Most Hickok tube testers neither test tubes under the actual operating conditions of their tube data sheets or circuit parameters, they are only a tool to give one an indication of a tube's function under a single set of operating condition based on known data at that operating point (i.e. the unit roll chart). The derived value "Gm" is only an approximation and there is a lot of variability between different models (and even the same model). The idea of calibration is model specific to take some of the variability if intra-model variations. The difference between models and other tube testers is because of both the test circuit, but more importantly a different set of operating parameters. The actual Gm number is just that, under those test conditions for that model.

A bogey tube can be calibrated using a curve tracer (amplitrex, uTracer, etc.) and/or a bench setup, the results in my experience have been close between these tube testers and a specific tube's operating curves can be compared to the manufacture's tube data of the era. One can also measure the tube tester's operating parameters, and compare these curves or the specific tube tester operating point and usually the Gm results will be quite close (withing about +/-5%). Surprisingly I did check a number of the more common tubes on an Amplitrex, uTracer, bench jig, Hickok 580A, 539B, TV-7, AVO CT-160, etc. and the test results were comparable looking at the same operating voltage points on each tube tester. The tube testers I use all have digital readouts for the operating voltages, so it makes it easier to determine each tester's operating conditions.

There are other factors that cannot be factored in like the DC grid supply on the RD-1575, KS-15750 and 580A, which will give erroneous reading unless one adds a switch to choose between filtered and unfiltered bias. Thanks to Mike Higgins on pointing this out and a lot of other extensive information/recommended modifications on these Hickok testers. The Hickok power supplies are not regulated, the voltages can change significantly under testing, so you can see significant difference between models especially when testing more power demanding tubes. Small adjustment in the line voltage also have a significant impact in the Hickok's measured tube values. So there are different approaches to how one determines Gm, some more precise then others, but the Hickok tube tester circuit does give viable reproducible results within the same model. Just understand that these are not precise instruments. A bogey tube can be setup for a specific Hickok model's operating points and it can be used as a reference to check a units calibration, nothing more.

I primarily use a uTracer 3+ these days because it gives a set of operating parameters over a range of operating conditions, so the Gm curves may cross at a plate voltage of 150V and be completely different everywhere else. YMMV.


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 Post subject: Re: Updated Hickok 539 Calibration document
PostPosted: Mar Wed 07, 2018 6:27 pm 
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Joined: Apr Wed 13, 2016 1:23 am
Posts: 112
Location: Independence, MO
Mike Higgins,
Thank you for the update. Can't wait to dive in.

Jim


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