NIXIE Clock/FM Radio. Nixie problems

[glatocha]

Hi,

I am designing the NIXIE display FM Radio with Clock/Alarm capabilities.
It is a modular concept and right now I am soldering and resting the NIXIE display.

I am using LC-516 lamps, that I've got from the auction long time ago.
I am supplying the Anode with ~220V and rectifier, measured DC is about 220, but it is actually just rectified 220AC not a clean DC.

Anyway as you can see on the photos, I have got quite clean digit passing current through 100k resistor (I have tried also 10k and 50k).
And all the digits light quite nice, except the digit 1. When I power 1, looks like the whole lamp is glowing.

Do you know what can be the reason?
Best regards

[NickAmes]

Have you tested your other Nixie tube? The problem could be caused by an internal fault in the tube.

[N2IXK]

I agree, looks like a bad tube to me. Contamination or sputtering damage to the #1 element.

[Macbeth]

When you say "soldering and resting" do you mean you are actually soldering the tube to the PCB rather than plugging it into a proper socket, or a cheaper DIY made up one using socket pins?

Quite apart from the fact that tube pins are nearly impossible to solder anyway, soldering a Nixie or any vacuum tube is a definite no-no. Even for the very reason that these things don't often have a good lifespan and fail and need simple replacement. You wouldn't solder your households lights rather than use the regular twist or screw fit instead would you?

Also, my own Nixie has a DC-DC HV switch mode converter that can up 5V to 190V DC. However I am led to believe the tubes, IN-12B, are actually designed to run on 240VAC with a half-wave rectifier. I really hope you are using a small isolation transformer, even a DIY one, if you are running them in this mode!

ETA:  blowing up the pics it looks like they are socketed. Try swapping the tubes around, but that seems too obvious!

ETA2: Why do the "sockets" if that is what I think they are appear to have melted gouges in them, like you have prodded them all with the tip of your soldering iron???

[Paul Price]

To get all this light out of a nixie seems to suggest a wiring mistake, it's just too bright for 100k resistor.
Why are there three wires shown connected to the board and what do they connect to?
Are you sure you are connecting the "1" digit in the nixie trough a limiting resistor >=100k?
Why is the center socket being used to select an element, rather then the other two sockets that look like they should be the ones connected directly to the elements?

[calexanian]

As mentioned. There could simply be too much current in the 1 digit. Since 1 has the least surface area it tends to ionize the brightest. Typically its the furthest away from the screen to raise the voltage drop and lower the current a bit, but you may need to add more resistance. Try 470K or so. If it begins flickering lower it a bit more until it stops.

[glatocha]

Thank you guys for all the answers.

Unfortunately the tubes are soldered in. I couldn't find the sockets, but might try to look again. It was not so difficult to solder, I just needed to scratch the pins a little as they are aged.

I need to do some more tests, and measures. When I tested the tubes before soldering, they were fine, maybe damaged during solder or there is a wiring mistake. I am thinking maybe swapping anode and "1" can cause that effect.

The tube is powered from 220 to anode via 100k resistor. The cathode is pulled to ground via transistor. There are three wires: White for high Voltage, blue for ground and red one is low voltage (5V) to the base of the transistor (via 1k).

In total on the board are 24 lighting elements. 2 tubes and 4 neon lamps. So there are 3 shift register sockets, that's why I am using the middle for "1".

Thank you all for the answers. I will try to do some more testings. But maybe only after the weekend