Help with IV-12 VFD Clock "Jenny"

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10 years 5 months ago #2850 by blinkman
Hello! I'm new to the forum and to Nixie builds, and not quite an electronics expert, but pretty well experienced with electronics assembly and soldering. In other words my work is neat and careful, but I'm not savvy enough to troubleshoot circuits if something isn't working quite right.

And I have a situation like that now: I've built the IV-12 "Jenny" clock (from the wonderful nixiekits.eu) and it's not a total success. All functions are working correctly, but the actual number display doesn't look right. The "unused" segments for each digit, which should be "off" or near dark, are slightly lit, and flickering a bit with the changing numbers. This makes the clock quite difficult to read, and comparing mine to the photos and video I've seen of this clock, I'm sure it isn't working right.

The effect looks worse in the photo than it really is, but you get the idea:



I have checked my work again and again, including placement and orientation of every component, and every step of the build instructions. The voltage tests in the instructions were all perfect. I can't find any poor solder joints or accidental bridges. Now I'm out of things to check, so I turn to you here for help! If anyone can suggest anything to check or try, I would appreciate it very much.

Thanks,

c.
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10 years 5 months ago #2851 by Ty_Eeberfest
Mr. Nixie himself is a member here; he is best qualified to answer your question. Until he gets here you can try the following things, which are what I'd start with:

- Resistor Network RN1: double check that it's the right part. (e.g. 100K, not 10K or 1M or something)

- RN1 again: are you sure you didn't mount it backwards? That could definitely cause the problem you are seeing.

- Check for missing ground at: RN1 common, IC8 pin 8, IC9 pin 10.

- Less likely, check for missing +5V at IC8 pin 16 or out-of-spec +HV at IC9 pin 9.

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

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10 years 5 months ago #2853 by blinkman
Thanks very much for the suggestions!

To my astonishment (and no small amount of embarrassment) I discovered I had in fact installed RN2 the wrong way around. I am completely amazed to see that I had missed this again and again! (This does terrible things to one's confidence as a builder...)

But it's good news to have found the (likely) cause. Unfortunately I wasn't able to remove the thing without destroying it, so I've ordered a replacement and will follow up here after it gets here and I've installed it.

c.

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10 years 5 months ago - 10 years 5 months ago #2854 by Mr.Nixie
Replied by Mr.Nixie on topic Re: Help with IV-12 VFD Clock "Jenny"
Hello,

yes I'm also here. It looks that all gates of the tubes are not correct tied (via RN2) to GND when not accessed through IC7.
Try the following: First disable the leading zero suppression so that all tubes are active. Than shorten Pin 1 from IC7 to Pin 10 = short circuit to GND. This should completely disable the most left hand tube.
If the tube is not completely turned off than there's a fault on IC7 or RN2. Do not direct short ciruit the gate (or the corresponding output Pin 18 of IC7 to GND) as the source driver IC7 will be overloaded.
Last edit: 10 years 5 months ago by Mr.Nixie.

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10 years 5 months ago #2857 by Ty_Eeberfest

blinkman wrote: Thanks very much for the suggestions!

To my astonishment (and no small amount of embarrassment) I discovered I had in fact installed RN2 the wrong way around. I am completely amazed to see that I had missed this again and again! (This does terrible things to one's confidence as a builder...)

But it's good news to have found the (likely) cause. Unfortunately I wasn't able to remove the thing without destroying it, so I've ordered a replacement and will follow up here after it gets here and I've installed it.

c.


Mistakes happen to everybody. I've been building off and on for 40 years and still make and overlook the occasional glaring error B) .

Glad I could point you in the right direction. I see I don't quite get it right myself: I was so busy looking at segment drive that I didn't grasp the significance of the key words in your post ("flickering a bit") that point the finger at digit drive. But bottom line is that if either pull-down resistor network was installed backward "ghost segments" can be expected since the driving chips are designed to source and not sink current.

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

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10 years 5 months ago #2889 by blinkman
Fixed! RN2 replaced, right way around this time. The clock works perfectly now! :cheer:

Thanks again for the help. I love this kind of international community support experience, that never could have happened before the internet. We live in a pretty cool time.

c.

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