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IN-1 nixie tube - fuzzy digits when driving with TPIC6B595

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StillTrying:
So what's the final fuzzy digit solution(s) ?

schmitt trigger:
How fast are you multiplexing the tubes?

There was a Nixie app note, from Burroughs if I recall correctly, which mentioned the fastest multiplexing was in the whereabouts of 140 Hz.

Not saying this is your case, but as an experiment could you slow the multiplexing to a very slow rate, such that you can see the individual Nixie being lit up?

EDIT: if you have an oscilloscope, what does the anode voltage waveform looks like?

2shy:

--- Quote from: schmitt trigger on February 05, 2020, 04:10:50 pm ---How fast are you multiplexing the tubes?

There was a Nixie app note, from Burroughs if I recall correctly, which mentioned the fastest multiplexing was in the whereabouts of 140 Hz.

Not saying this is your case, but as an experiment could you slow the multiplexing to a very slow rate, such that you can see the individual Nixie being lit up?

--- End quote ---

I'm not multiplexing, they're supposed to be driven statically.
Actually, the first nixie clock I made was multiplexed, I used a single 74141 to multiplex 6 tubes @ 80 Hz, it has a cathode depoisoning sequence when HH=MM=SS. I also implemented dimming the tubes at low ambient light. It's working flawlessly at my home three years now. You can see it working here (tube flickering on the video is not seen in real life):

and see the simplified build process:
https://goo.gl/photos/6rs2Qc8VyK6q7ynN8
Here's another version of the same clock, but with different tubes LC-516 (Polish ripoffs from Russian IN-1, I did a double footprint) - I personally like this one much better.
https://imgur.com/a/NXRS8

I made another version with IN-1 tubes and wanted them to be statically driven, so I chose to use TPIC6B595. And now it seems it wasn't the best solution :/
I'll try to look at the anode voltage.


--- Quote from: StillTrying on February 05, 2020, 03:55:47 pm ---So what's the final fuzzy digit solution(s) ?

--- End quote ---

Just as your nick... StillTrying to figure it out.
I didn't have much time to tinker with the circuit in the past two days.
I'll update the thread as soon as fuzzy digits start to light properly.

2shy:
Okay, I finally had some time to look at the PCB and fortunately was able to solve the problem.
It's really embarassing, but I have to confess - it turned out that some nixie pins didn't make any contact with PCB pads  :palm:
I noticed it while measuring cathode voltages - the pins and the pads had different voltages. Then I turned everything off and tested the 'press fit' connection using continuity tester - two or three cathodes were unconnected. I soldered the pins to PCB and now everything works as expected.

I'm glad that the problem's solved, but ashamed of the reason.
Thank you all for your comments, I learned the lesson. Next time I'll probably replace TPIC6B595 with something more suitable, as using this IC for driving nixie tubes is not the best engineering practice.

schmitt trigger:
No need to be embarrassed. Everyone , and I mean everyone has made a foolish mistake...at least once.

For me, it was assuming that the band on a tantalum cap was also the negative terminal, like most aluminum caps are.................
The results were spectacular.  ^-^

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