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    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Retro nixie volume indicator

I build the Nixie volume indicator From the "as build" schematic. Sadly no joy, multiple numbers light up at the same time and changing the sensor pot doesn't make a difference. I double checked the PCB I made and that seems ok. I think I got some bad 74141's. The inputs are switching between 0 and about 4,5 volts when changing the sensor pod, so that's ok, nothing happens with the outputs though. Tonight I will remove the 74ls75 and manual connect the inputs of the 74141 to ground and see what happens, but I've got the feeling I need to go hunting for new 74141's [emoji24].

Ronny, can I ask why you chose for 22k as anode resistor? It seems a bit high to me. Is it to preserve the Nixie life? I could be completely wrong of course but just learning and trying to understand.

And just in case, do you know where to buy the 74141 in Holland?
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So tonight I connected all 4 inputs of the 74141's to ground to make sure that they were low, that should result in a 0 displayed. That didn't work, Vcc is present, gnd is connected, so I guess the 74141's are really defective. Even with the 74ls75's removed multiple numbers are displayed. I removed the 74141's also and manually connected the output pins to ground, that works and shows the correct number corresponding to the output.

Found a seller of K155ID1 Nixie Drivers and ordered them, I hope that solves the problem. I really like this volume indicator and hope I will get it to work....
Excellent project Ronnie!
I will definitely built this Volume indicator and add to my upcoming tube preamp kit project!

I have IN-1 tubes they are a little larger in diameter and require 200V (I think that's the only difference) All I will need to do is bump up voltage on DC/DC PS right?

Thank you!
Hello Ronny
-Two Years Later

Looks like I made an OK PCB, collected all ICs, some caps was in allot higher voltage, but I could not spend any more $ and I want to see this working, so I used what I had (it's only 3 components) the rest as per your schematics.

Everything looks right, but displaying not working right, only one Nixie is displaying, and it's showing random numbers, sometimes multiple segments glow together.
When I adjust Sensor POT I do see, Nixie reacting, but it never stops, numbers continue to change, even if stop adjusting it
On CA3162 pin 8 and 9 - 47k "0" adjustment, also makes changes on the same nixie indicator, but again also random numbers
Second indicator does not light up, I did check the tube on bench PS with 10k resistor on anode, and it's glowing.

Anode viltage on small red eBay power-supply is 160VDC
All ICs are getting correct power

Do you know what can possibly cause this irrational behavior?

Thank you.

Thank you very much.
Yes, green wires are 12V for DC/DC PS.
Valentinas33 from eBay change the board a little since your original build, board is now wider and 170V pin is swapped with GND now, so caught that before making PCB, but board size, I think missed something in my calculations, so now I have ho;es on the red PCB not aligned with green PCB

Thank you.


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Lets start with checking the nixie driver IC, nixie and hv power supply. When appling a BCD code on the inputs of the nixie driver the correspondent number should light up. Look at the table below.

Remove the latch buffer 74ls75 before the nixie driver k155n out of their socket. Now you have access to the ABCD inputs to the nixie driver. Apply with four wires a code from the table. 0 = 0V and 1 = +5V. Please confirm that the right number lights up. Do that for both displays.

Sorry I was on vacation :)
Before I remove Counter and Trigger, I would like to tell you what's happening after I corrected pinout on nixie tube, and reinstalled Buffer back in the socket.
I was able to set 0 with 47ohm trimmer on Counter pin 9 and 8, and now when I turn "sensor" pot I get 0,1,2 and 3 but not smooth, it's like 0+1 glowing same time till halfway, than I have 1 for little wile, in between I get all 3 digits glowing, and at the end I have 3... Is it possible that my 47k sensor pod is bad? I don't see any other segments to glow other than 0,1,2 and 3 in weird order, and second nixie still dark again