Digit Brightness, Classic Rev6, IN-8 Tubes

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7 months 3 weeks ago #12798 by Ty_Eeberfest
Jedidiah,
Okay, that intermittent firing would compensate for the 1K anode resistors but I don't see what they are trying to accomplish. Their circuit is direct drive so why not fire the tubes constantly (that's kind of the point of direct drive!) and use appropriate anode resistors? The reality is that they are exceeding the tube's specs with those high pulses regardless of whether the average is okay. The specs seem to speak in terms of constant DC current, not the average of big spikes. And, the consensus of opinion seems to be that the peak current, not the average, is what affects tube life. But if it works for you, so be it.

Torsten,
Unless I've misunderstood something I don't see how your ZM1350s can be poisoned in the traditional sense (sputtered cathode material) since the cathodes are co-planar rather than stacked. Seems to me that any sputtered metal would end up on the glass (or rather its coating), not on the other cathodes. Not sure about the getter.

My only Panaplex experience is with SP353 7-segment devices which appear to not have a getter. A couple of my SP353 clocks have been running for ~8 years with no visible deterioration. They are direct drive, no ACP routine. Anodes +180VDC with no resistors. Resistors are on all the cathodes, 120K or 150K or 330K as appropriate for the various sized cathodes.

Look into it later when the dust is clearing off the crater.

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7 months 3 weeks ago #12799 by Jedidiah
Here are the Maximum Operational Values from the IN-18 datasheet (full copy attached):



So I wouldn't say that he is running out of spec, at least not in any significant way.

From his writeup (again, not perfectly clear), it seems that he was trying to accomplish 3 things:
1. Increase tube life
2. Maintain digit brightness
3. Avoid cathode poisoning

And he claims that he did:

"At the same time the brightness of the tubes using this scheme did not affect the brightness!
So at the end the lifespan of the tubes finally increased SIGNIFICANTLY in comparison to the manufacturers statements!!!"

Based on his clock, one of which I own, I certainly cannot refute his claims. I just thought it was an interesting and novel approach - perhaps a bit "out of the box."

For me, and for this thread, I was obviously associating his approach with the IN-18s as a possible solution to my IN-8 brightness issues in the Classic Rev6 multiplexed design.

Thanks again to all for the valuable comments and insights!!
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7 months 3 weeks ago #12802 by Ty_Eeberfest
I disagree with your interpretation of the data sheet. Please take another look at it.

The concept of average current is not addressed on the data sheet. "Anode current at pulsed voltage" specifies to the peak allowable current in pulsed operation. "Anode current at rectified DC" specifies the current for pure DC operation - constant DC, no pulsing or MUX or whatever. Thus 18mA peak pulse is exceeding the max pulse spec of 4mA, by 14mA.

That's how I read the data sheet but if those 18mA pulses are working for you then great. I'm skeptical of "breakthrough discoveries" by someone who can't even make a coherent write-up though, especially since Nixie science has been around for ~65 years!

If you want to try this pulsing scheme in your Classic you will obviously have some programming to do. I'm fairly familiar with the internal workings of that code, so I'll warn you that it isn't going to be easy. If you try to extend the anode pulses you will run up against MUX timing issues that will be created by the change.

Or you could just change the resistors, leave the code alone, and see what happens... :dry:

Look into it later when the dust is clearing off the crater.

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7 months 3 weeks ago #12803 by Jedidiah
The spec statement in full is:

"Anode current, at pulsed voltage
(50Hz), mA (median)"

In this case, what does the term "(median)" refer to?

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7 months 3 weeks ago #12804 by Ty_Eeberfest
Good question. According to Webster the median is:
"The middle value in a distribution."
which seems a bit nonsensical in this context. What "distribution"? If it said "mean" (another word for average) rather than "median" then I'd have to concede that your interpretation is correct. But it doesn't say mean. Is the English data sheet a bad translation of the Russian? I can't say.

Look into it later when the dust is clearing off the crater.

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7 months 3 weeks ago #12806 by Ty_Eeberfest
I just tried typing the Russian words into Google translator. Easier said than done. Several characters on the rather blurry PDF could be any of several different similar looking characters on the Cyrillic keyboard. Results were rather ambiguous: By guessing at the unclear characters I can get "middle" or "middle class" or "mean" or even "mean value" as the translation.

Hmmm. Since your tubes are not burning up I'm thinking "mean" is the correct translation.


Look into it later when the dust is clearing off the crater.
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