Newcomer From Asheville, NC 5991 vs IN-12

[Tom Lang]

I'm a retired electrical engineer familiar with designing and building vacuum tube amplifiers.  This is my first foray into the nixie tube clock world.

I want to use the Burroughs 5991 tube on some pcb boards designed for the IN-12 tube.  I have looked and looked but cannot find definitive answers as to physical interchangeability of the two especially on prefabricated pcb boards designed for the IN-12.  At this time I do not have any of the tubes or boards on hand.

It appears (see attachments) that the 5991 has two extra pins 13 & 14 that would have to be accommodated if one were to utilize a 5991 on a board for the IN-12.  However, the picture of the "tube adapters" implies otherwise (where's the holes for 13 and 14?).  Also it DOES appear that chassis mount sockets (such as the brown ones shown) do have relief holes for the extra 5991 pins.

There are attractive prices for premade boards for the IN-12 tubes that I probably would purchase if they are compatible with the 5991.  However, I don't mind having to use chassis mounted sockets and flying leads if necessary for the 5991.

Thanks for your help.

[Tom Lang]

Some insight as I was thinking about this.  I looked at some pcb sockets.  Apparently pins 13 and 14 are not carried thru the actual socket itself.  This would imply that as long as the tubes were not directly soldered onto the pcb board itself (I would expect no one to do this) a board for the IN-12 could accommodate a 5991 after all??

[Michail Wilson]

Hello,

 

Pin 13 and 14 are not used.  Most sockets (if not all) will have an open area for the pins to slide in even if no connection is made.  For that tube, you could literally simply cut them down (carefully) so you don’t have to worry about it like in the circuit design you included a picture of (pcbway?).

 

Very few tubes use those pins (like the B5971) so finding the sockets loaded with all 14 holes is rare in itself.  When I spot them on ebay, I snag them (for no real reason other than just knowing they’re rare).  I love the auctions where people post pictures of tubes with sockets (14 pin complete) and selling for the cost of a $5-$10 tube.   Those sockets are worth more than the tube itself.

 

I believe the 5991 is pin compatible with the IN-12    (That is IN-12A.   The IN-12B uses pin 12 for the leading decimal point where the 5991 and IN-12A don’t have it.

 

(So, unless you’re using a B5971, you don’t need sockets with pin 13/14 loaded with connecting gear)

 

M1

--
You received this message because you are subscribed to the Google Groups "neonixie-l" group.
To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+...@googlegroups.com.
To view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/f5f96fac-3906-4457-996d-54749fd39815n%40googlegroups.com.

[Dekatron42]

There are slight differences between the B5991/2 and the IN-12A/B pin spacing according to datashets, dimensions can be found here:

IN-12:  IN-12A_IN-12B_03.pdf

B5991: https://frank.pocnet.net/sheets/116/b/B5991.pdf

Overall dimensions is in inches on the B5991 and millimeter on the IN-12 which makes the two tubes almost fit in each others sockets. The sockets I've tested puts a lot of strain on the pins possibly leading to cracks in the seals of the tube pins if pressed in to hard, either directly or over time. The Burroughs type has a total lengthwise distance of 0.68 inches whoch si close to 17.3mm whereas the IN-12 is specified at 18mm, the other direction the Burroughs types is 11.2mm whereas the IN-12 is 11.5 (not much of a difference) but the other way it is almost 0.7mm which is quite a lot.

Neither do I recommend cutting off pins on Nixie tubes as that will probably lead to cracks in the seal, there are flying lead Nixies like the B5750 or IN-16 and even on those you shouldn't cut the pins to close to the glass seal nor should you solder to close to the glass seal as the high temperature from the soldering iron might lead to cracks as the pins expand in the glass seal.

Since I discovered this difference I've always used the correct sockets for the specified Nixie, or used single pins.

/Martin

[Leroy Jones]

Absolutely correct!    The Russian tubes are metric.   The USA tubes are in inches.    Close but not an exact match.

Using the incorrect socket puts a stress on the pins and will crack the glass.    The glass seals around the pins are by far the

most delicate part of a tube.    Avoid heat and mechanical stress on tube pins.   I have learned this the hard way over the past 40 years!

[Michail Wilson]

It depends on who you ask.  The sockets have floating pin connectors.  I’ve used them interchangeably for years without issue.

 

B-5991 datasheet says to use socket SK-136 (PL31A-P)

IN-12 says to use socket SK-144

 

https://www.tube-tester.com/sites/nixie/data/soc/SK-136-14pin-chas/SK-136-14pin-ch.htm

 

 

M1

To view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/4df433e6-34c7-4dc0-9265-d718acbbc8e4n%40googlegroups.com.

[Dekatron42]

There's a big difference between the Russian sockets and the Burroughs sockets - the Russian sockets have a two prong grip (like two prongs on a fork) on the pin which is a lot more unforgiving compared to the funnel (tube) type on the Burroughs sockets. In the Burroughs sockets this funnel moves freely in all directions, in the Russian socket these two prongs only move along the slit they sit in and they don't give as much as the Burroughs type do.

If you can't get hold of the proper socket use loose pins and bend them slightly if needed.

/Martin

[newxito]

I prefer loose pins. For my current project with IN-18 tubes I need to hide these pins, so I will design a 3D printed “socket” to cover them. With a material like galaxy black they will look great… hopefully :-)
This method also helps if you want to implement LED underlighting. The hole in the center of this IN-12 socket appears to be very small.

[Tom Lang]

Thanks for this info!  Just what I needed.

[Nicholas Stock]

I can confirm that the B5991s will work instead of the IN12 if you're using the long nixie pins that have some flexibility in them (not sockets...)....here they are in (the last) green PCB KoolKlox.....

Cheers,

Nick

To view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/5dd93c0a-4aef-420f-a0a1-dcf02c79952dn%40googlegroups.com.

[Mac Doktor]

On Aug 10, 2025, at 8:01 PM, Nicholas Stock <nick...@gmail.com> wrote:

I can confirm that the B5991s will work instead of the IN12 if you're using the long nixie pins that have some flexibility in them (not sockets...)....here they are in (the last) green PCB KoolKlox.....

Do they still make translucent PC boards like that?

I had a pile of big video game boards here and let all of them go except for the one with that special magic. Someday I'm going to put a light behind it...

Terry Bowman, KA4HJH
"The Mac Doctor"

https://www.astarcloseup.com

“...the book said something astonishing, a very big thought. The stars, it said, were suns but very far away. The Sun was a star but close up.”—Carl Sagan, "The Backbone Of Night", Cosmos, 1980

[Nicholas Stock]

Just the backlight enhancing that, it looks like a regular green PCB in real life...

Sent from my iPhone

On Aug 10, 2025, at 18:29, Mac Doktor <themac...@gmail.com> wrote:



--
You received this message because you are subscribed to the Google Groups "neonixie-l" group.
To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+...@googlegroups.com.

To view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/2D3C6F4A-6690-4E76-82B9-B39B91F8D872%40gmail.com.

[Peter Hall]

I luv me  KoolKlox,made by the man,from Stock Clocks😄...I suggest you get ya hands on a Green board(the last) as the New ones are Black and just as Sexy in there own right🚨....I luv the Orange leds, shoulda been called,a insidiousnixies option🦘...lol..gotta a couple off boxs,too send and will contact ya,Nick....

From🚨Peter Hall😁 insidiousnixies🦘Utube

To view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/3FD2D4EA-D838-42E3-83C4-02582A5EA733%40gmail.com.

To view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/3FD2D4EA-D838-42E3-83C4-02582A5EA733%40gmail.com.

To view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/3FD2D4EA-D838-42E3-83C4-02582A5EA733%40gmail.com.

[newxito]

That's a really kool clock, I want one! Does it also work with 230V 50Hz?

[Peter Hall]

I'm in Australia and yes its running on 240v 50hz...l get me hands on one off the last Green Boards...Looks like Nick at Stock Clocks,has one ready too go..Look him up on the internet..Just put Stock Clocks and he'll appear👍

From🚨Peter Hall😁 insidiousnixies🦘Utube

--

You received this message because you are subscribed to the Google Groups "neonixie-l" group.
To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+...@googlegroups.com.

To view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/3642eb88-d54a-4dde-b283-a4cef12939afn%40googlegroups.com.

[Peter Hall]

Thx Mate,just me mums,Bal,for pension too Dementia Centre,That Bank"Wales" Nolonger exsisits now..So all good...

From🚨Peter Hall😁 insidiousnixies🦘Utube

[Tom Lang]

I wonder if you can buy just the bare pcb?  Or request a board color of your choice from a pcb fab house?

[Nicholas Stock]

Only black PCB kits left I'm afraid. No plans to order any more after this batch is done (PCB costs are a lot higher now due to the current 'climate'). The original design was by Matt Abraham and he sold me the 'rights' as it were about 5 years ago as he wasn't interested in selling kits etc any more. I gave the case a bit of a refresh, updated the manual and bought (nice) matte black PCBs as I prefer the look.

https://www.instagram.com/p/C3ys8JKLIwh/

You can find all the details here..

https://stocksclocks.com/index.php/koolklox-ttl-nixie-clock/

Cheers,

Nick

To view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/1d2ff4c2-1cb3-421f-8bb1-3f36823b8c4fn%40googlegroups.com.