Do Russian IN12 sockets work for B5991 / NL8422 tubes?

[Tom Katt]

Tried to search around but did not find anything conclusive...  I've got a bunch of B5991 / NL8422 nixies and I'm finally getting around to building a project, but I don't have sockets.  I've never owned any Russian IN12 tubes, but they look like clones of the B5991's...  Does anyone know if B5991's fit into the IN12 sockets?  Genuine US sockets are somewhat pricey on eBay and the Russian IN12 sockets are much cheaper...

Thanks!

[Oskar]

This was discussed recently. See here.

[Tom Katt]

On Wednesday, December 17, 2025 at 10:11:54 AM UTC-5 Oskar wrote:

This was discussed recently. See here.

Actually, I did see that thread...  but I'm not certain what to make of it.  Other than the comment that the Russian tubes are metric and the US tubes are fractional inch so there is a difference and then the discussion goes on to suggest using bare pins.  I understand it may be a tighter fit, but is it possible?  Nixie's don't get replaced very often, so once I get them in the socket they will likely remain there forever. 

The US sockets are priced about the same as what I paid for the tubes themselves lol.  VS about $20 shipped for a set of 6 IN sockets.  If I could think of a way to mount the tubes on a backing plate, I'd probably just buy the single pins.  Oh well.

[Tom Katt]

I may have answered my own question - of all places, Sphere Research's old archived website has this to say about IN12 sockets for sale:

12+2 Pin Russian mil spec oval sockets, part number PL31a-p, designed for the Russian IN-12 Nixie, but also fit most oval pattern Burroughs and National numeric tubes, like the 8422, B-5991, B-59917A, KS-19944L1, etc. Sockets are marked with pin numbers (same format at the US tubes), solder tag contacts and have a molded in 2-hole mounting flange. The two center pins are simply clearance holes (pins 13 and 14), as they are unused on the IN-12, and rarely used on other tubes of this mechanical format. Slightly snugger fit than US sockets, but work great on both types of tubes.

Sphere continues to be an asset even after they're gone ;-)

[Leroy Jones]

I would advise being very cautious regarding the tightness of the fit of the tube pins into ANY socket!    Certain sockets are so tight that they

tend to put a side-loading spreading force on the tube pins enough that in extreme cases the glass tube base will crack.   My standard procedure now

for any such socket for tubes such as NL6844A and 8422 is to use a tapered aluminum soldering probe to wallow out each socket pin to a much looser fit on each tube pin.

If you go too far and open the socket fork too much, you can reach in there using a pointed exacto blade and add back some tension.   Sockets adjusted that way give the tube

a very easy and buttery feel going in and coming out of the socket, yet they retain good contact.   Those russian socket pin forks are some real doozers last time I checked.

As I recall they are massive thick things with practically go give at all.    My impression of them is they will destroy a tube in a New York minute!    My advice is STAY AWAY

from those russian sockets by all means.    Get the good USA made green ones and carefully open them up for a nice fit.  Your tubes will then not break.

[Tom Katt]

On Wednesday, December 17, 2025 at 11:31:23 AM UTC-5 Leroy Jones wrote:

I would advise being very cautious regarding the tightness of the fit of the tube pins into ANY socket!    Certain sockets are so tight that they

tend to put a side-loading spreading force on the tube pins enough that in extreme cases the glass tube base will crack.   My standard procedure now

for any such socket for tubes such as NL6844A and 8422 is to use a tapered aluminum soldering probe to wallow out each socket pin to a much looser fit on each tube pin.

If you go too far and open the socket fork too much, you can reach in there using a pointed exacto blade and add back some tension.   Sockets adjusted that way give the tube

a very easy and buttery feel going in and coming out of the socket, yet they retain good contact.   Those russian socket pin forks are some real doozers last time I checked.

As I recall they are massive thick things with practically go give at all.    My impression of them is they will destroy a tube in a New York minute!    My advice is STAY AWAY

from those russian sockets by all means.    Get the good USA made green ones and carefully open them up for a nice fit.  Your tubes will then not break.

Thanks very much for the advice.  Although I could probably manipulate the Russian sockets to work, I agree that you'd never know if mechanical stress will cause issues or breakage down the road - especially with thermal cycling.  I have decided to not be stingy and just fork over the $ for US made sockets.  My experience with other Russian hardware is that frequently costs are cut to bare minimums and the quality often suffers as a result.

It's curious how the Russian designs are basically cloned by the American products...  and yet modified to require their own pin layouts.

[Leroy Jones]

Back in year 2010 I lost a few perfectly good NL-6844A tubes to some of those "killer sockets".   That very painful lesson was what

it took to show me how and why certain sockets are very bad!    I had just built the smaller clock with the 6844 tubes.   Had it running for a few days

when one tube went dark.   It had a cracked base.  Changed it out and started testing again.   Later same day it failed again.   Then took clock all apart

and closely examined the sockets.    Turned out I had 2 different types of sockets.   There were some good ones that have very thin and springy forks.

Then there are others which I have since dubbed them "The Tube Killers".    Those have very thick and very stiff forks.   Later testing revealed that those killer

sockets can be tamed by adjusting with the tapered probe to open up the fit.   But I still do not like them because even loose, they still side-load the tube pins.

Here is a link to a video of two of my clocks.   The smaller one has the NL-6844A tubes and it is the one that had the broken tubes due to the bad sockets.

https://youtu.be/gJ84ItTar-g

[Tom Katt]

On Wednesday, December 17, 2025 at 12:11:14 PM UTC-5 Leroy Jones wrote:

Here is a link to a video of two of my clocks.   The smaller one has the NL-6844A tubes and it is the one that had the broken tubes due to the bad sockets.

https://youtu.be/gJ84ItTar-g

I love your clocks!  A man after my own heart... did you see my recent post? - a bit similar ;-)  I like the keypad on the big one!