Modular Nixie Clock Rev3 keeps restarting

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4 weeks 1 day ago #10468 by jjansen
I just completed the build of the Modular Nixie Clock Rev3 (FW 356).

It is working a little bit. But it keeps rebooting. It looks like the frequency of reboots is depending on the brightness of the tubes. When the brightness is high (for example during setup) it keeps restarting. When the brightness is low, the time between reboots is much longer.

VCC is about 4,8 - 4,9 Volt
170 measures about 170-180 Volt

Some vids
Issues during start-up sequence:


'Normal' operation
12:xx is initial time
17:xx is time from WIFI


Any idea what might be the problem?

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4 weeks 2 hours ago #10469 by Ty_Eeberfest
Sorry for the late response. The usual suspect for spontaneous reboots is the external power supply. I'm not sure what voltage you are feeding to the clock board, but if you happen to a 12V supply rated at >= 0.5A (bench supply maybe!) try using it. Do a factory reset (hold down clock's button as you apply power) and do the HV calibration, see how it goes. If that doesn't fix it we can then dig deeper.

(Yes I know the instructions say to use a 9V supply, but my personal experience is that 9V is borderline. I have a Modular sitting next to me here that has been running off 12V for over a year with no problems. On 9V it was never able to reach the HV target. Just sayin'!)

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

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3 weeks 6 days ago #10470 by jjansen

Ty_Eeberfest wrote: Sorry for the late response.

No problem ;-)

Ty_Eeberfest wrote: The usual suspect for spontaneous reboots is the external power supply. I'm not sure what voltage you are feeding to the clock board, but if you happen to a 12V supply rated at >= 0.5A (bench supply maybe!) try using it. Do a factory reset (hold down clock's button as you apply power) and do the HV calibration, see how it goes. If that doesn't fix it we can then dig deeper.

I used a 9V 1A supply at first. Then tried with a bench supply (converted ATX supply) at 12V, this one should definitely be able to supply enough amps.

Mosfet and power regulator don't get hot.

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3 weeks 6 days ago #10471 by Ty_Eeberfest
Okay, so we've ruled out the easiest possibility. Problem could be on-board power or it could be noise.

Noise:

- Make sure Pin 1 (reset) on the Atmega is held high - R13 present and correct value, connections good.

- Make sure all the electrolytic capacitors are the correct values in the correct locations, installed with correct polarity. Check this twice - it seems a lot of people get C1/C3/C4 mixed up for some reason.

- Long shot: see if lightly touching the 16MHz crystal aggravates the problem. There has been some talk about bad crystals lately.

Power:

Double check values, orientation, etc. of all passive components around the voltage regulator - refer to schematic.

Do you have anything that can monitor the +5V rail and record any dips? I'm thinking of something like my Fluke 83 meter with its MIN/MAX function. It would really help to know if the +5 is dropping out, even just for a few milliseconds. Also, is there any visible flicker or dimming of the power LED?

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

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3 weeks 6 days ago #10472 by jjansen
Ty, thanks for the suggestions.
First 2 photo's of the board.





C1 2,2 uF @ 400V
C3 220 uF @ 35V
C4 220 uF @ 10V

R13 = 10K, Reset pin of the ATmega is high.

Touching the crystal does not change anything.

Orientation of components around voltage regulator looks good.

I don't have a multimeter with min/max options. But I have a super simple DIY oscilloscope.
It's not well calibrated, bit it gives an idea about the voltage (multimeter reads 4,95 volts). It shows some very narrow spikes towards 0 volt sometimes (correspondents with the device resetting).


It is only happening while the high voltage generator is active. When HV switches off after 1 minute, the signal is much more stable.

So it looks like it has something to do with the power.

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3 weeks 5 days ago #10473 by Ty_Eeberfest
Thanks for the clear report! The board looks okay to me. I can't see D3 in either pic so I'm going to ask you to double check its orientation.

I think the scope trace explains the resetting. I'd like to know if that downward spike is appearing on VIN like it is on VCC. My thinking is like this: you said the HV generator seems to be involved in causing the spikes. But the HV generator runs off VIN not VCC (well, except for the gate pulse). If something is goofy in the HV generator, such as maybe the MOSFET occasionally "latching up" and drawing a huge current surge, you should be able to see it affecting VIN. Read VIN right at the board, not at the external power supply.

That's all I can think of to try at the moment. This is a strange one. I'm hoping Ian is reading here and has some other ideas.

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

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