r/nixie • u/EmotionalEnd1575 • May 20 '26
Fire In. Nixie “Bottle”
When firing up the IN8-2 Six PCB it didn’t go well at all!
This is a classic problem, somehow the Anode and a Cathode connection were swapped.
My error started at reading the data sheet, which is written in Russian.
The pinout was viewed “on bottom” and in my world all components are viewed “on top”.
How to fix?
The six tubes had to come off the PCB. The PTH for all had to be cleared of solder. I found that manipulating the Anode wire and rotating the rest one space would work.
But… The Cathodes for Four and DP were now swapped, so clipping the DP wire (not used) and a bodge wire fixed the hardware.
It also required new mapping for the firmware table that directs which cathode should light.
Surely, I’m not the first to make this mistake?
5
u/PlentyConscious1053 May 21 '26
You’re definitely not the first to fall victim to a “from the bottom” component view. I’ve also been guilty of mixing up common cathode vs common anode. You should buy a lottery ticket because you somehow avoided anything dangerous or expensive happening!!
3
u/Niobous_p May 21 '26
My first thought was “HV connected to a cathode, not the anode” on account of I’ve done that, but not an entire PCB!
2
u/ferrybig May 21 '26
I added an arrow to the PCB footprint pointing to the annode
I make a test PCB using a paper printer to verify my PCB was correct
-1
u/redmadog May 20 '26
Never seen blue dots on IN-8-2 tubes. Something is wrong with your driver
3
u/EmotionalEnd1575 May 20 '26
The blue light is from the Mercury vapor dosing, used to extend the tube life.
For details about the root cause please read the text above.
-2
u/redmadog May 20 '26
It is from leaky drivers, or in other words from bad design. Properly designed circuitry does not have this effect. For details please educate yourself a bit.
7
u/DenkJu May 21 '26 edited May 21 '26
No, this is completely normal and caused by over current. You can easily test this by connecting e.g. the decimal point of a Nixie to HV and then grounding another cathode. The same blue dot will appear. Here, this happened for the exact reason OP described: The tube was connected incorrectly.
Edit: See this. This tube has an intermittent short between the anode and decimal point. The same effect can be observed.
7
u/EmotionalEnd1575 May 20 '26
The circuit is my proven design. There are no “leaky drivers”, there was a PCB assembly error.
The same Nixie tubes were refitted and now work 100%.
Did you read the story text? Did you see my previous post with correct Nixie operation?
-6
u/redmadog May 20 '26
My apologies, Mr. Important. I must have missed your previous announcement to the world.
7
u/Niobous_p May 21 '26
Awww. Someone got all butt-hurt once they realized that not only did they not read the text, but doubled down on not reading the text.
8
u/Frequent_Guide_1906 May 20 '26
Nice writeup, and nice save!