NCT412 With 6 IN-12 Tubes & Neons Don’t Work

[smaxwellParticipant]

I just got done putting together a 6 tube IN 12 clock and the lamps/tubes won’t light up/display but the RGB LEDs/buzzer work. I have checked voltages at the test points and I’m getting the proper voltages(5v, 12v & 190V) and have continuity on the tube board(NCT412-6). I also have continuity from the high voltage driver to PDB-38. I’m wondering if something is not correct with the controller and if controller chips usually come with a black sharpie marked “B” and “F” on them?

[Jason MartinParticipant]

This is the same as what I have.

Mine also has the B and F in sharpie/marker on the atmega.

Question. Did you do sockets? If so, how close are they to touching the metal capacitors below the second Nixie?

Another question: Do you have the White or Black PCB?

Mine is black fwiw.

• This reply was modified 1 year, 5 months ago by  Jason Martin.

[smaxwellParticipant]

I have the black PCB as well. I did use the sockets for the tubes and trimmed the #2 tube sockets so as to leave a noticeable air gap between the sockets and the top of the capacitors. For added measure of protection I even have a layer of electrical tape placed on the capacitors.

It’s a great looking clock, can’t wait to see the tubes lit!

[Jason MartinParticipant]

Excellent! I was going to make that exact suggestion on the tubes!

I apologize for stepping into some Captain Obvious below:

Have your attempted to trace back from the sockets to the header for the HV and ground line?

Another area to look at is making sure that the diodes are all correctly oriented.

Also make sure that there isn’t any solder forming a bridge on the HV5122 pins.

These are the faster checks, but if you don’t see anything wrong with those, I can start taking measurements at different points to give you additional checks to perform. Caveat: do any checks that are not at the Test Points at your own risk! Some of them may be really close to other lines that might cause a bad short should you cross them.

[smaxwellParticipant]

I got it working😁

On your suggestion about the “solder forming a bridge”, I went back and checked my soldering again with the magnifier app on my phone. Turns out a couple of ground pins on the U2 chip didn’t look right so I added some solder to those pins and now everything works as it should.

Really appreciate your help Jason you got me looking in the right spot, thank you.

[Jason MartinParticipant]

NICE! Glad to hear it is working!

fwiw, I just found out about a Nixie Discord Server and I am in it now talking about the correct voltage to set the HV to for these clocks.

https://discord.gg/HPeBn2A

Hopefully that works.. if not here it is in long form

https
:
//
discord
.
gg
/
HPeBn2A

[Author]

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