GeekKlok Ver. 1

What is it?

This is nixie tube clock assembled from the "GeekKlok PCB Kit" and installed into a case I built.   The most obvious feature of the clock are the four vintage Burrough's B-7971 alphanumeric Nixie tubes.  Unfortunately, the GeekKlok has an unpleasant history that mars what should be an absolutely top-notch product.  In fact, there is an entire page dedicated to warning you not to do business with this guy.  In my case, I simply couldn't overcome the urge to buy a kit to use my sweet B-7971's, and against all my better judgment, entered into dealings with a most sketchy man.  I must admit that in the end, he was fair and honest, but sketchy, seriously sketchy.

The real motivation for tracking down this kit (the guy is in Indonesia) and building the clock, was to put to use some of the B-7971's my Dad recently gave to me.  Being an electronics nerd must run in the blood, because when I told my Dad I was getting interested in vintage display technologies, he quickly told me about the stash of tubes (and sockets!) he had hidden away at his office.  He couldn't remember what kind they were, but said that they were big, had driver boards, and were mine if I wanted them.  Little did I know that he was going to give me six boards (two tubes per board) from one of the now legendary Lectrascan Displays (really fascinating little article with some terrific photos).  Just for good measure he had stashed away a spare, bringing the total haul to 13 B-7971's and 12 Bakelite sockets!  It was like winning the lottery...

How does it work?

As the electronics are from a kit, I had nothing more to do with them than solder them all together.  However, there are some features that are worth mentioning in detail: 
  • The onboard DC-DC converter that produces the high voltage is a nice feature that lets you use a 16VAC wall-wart as a power supply (mains isolation, safety first!) and makes all the electronics compact (no bulky transformer).  I'm sure in its day it was a terrific design, but it requires the now obsolete MAX771 switch-mode controller.  The seller doesn't have any so you'll have to go to to Maxim and hope they still have samples. 
  • The clock relies on the local 60Hz (or 50Hz) as its time base and has a battery powered RTC chip for power fail back-up, the best way to achieve accuracy in my opinion.  
  • The GeekKlok multiplexes the tubes, which turns out to be one of its best features.  It keeps the part count down (just two DIP16 Darlington arrays and four MPSA92s), improves the life of the tube (it's off about %75 of the time), and apparently reduces the humming sound the B-7971 normally makes (I've nothing to compare it to myself).
  • 50 different fonts, including 24 animated fonts.
  • A whole slew of setting, from daylights savings time adjustments to auto dimming and date display.


The case is very minimal, just an aluminum base, delrin sides, and a thin acrylic cover.  I wanted something that was completely focused on the tubes, leaving no doubt to even a casual observer that these were very special objects.  The case is entirely machined, so everything fits together tight, has sharp corners, and every surface is finished.  I personally think electronics are more interesting when you can see how they work, and generally make the guts visible to enjoy.  I sprang for black-oxide fasteners, and am definitely enough of hardware nerd to admit that details like that really make a big difference to me.

A few more photos:

I told you those black oxide fasteners looked hot!

Such a beautiful technology

Don't you just love that plasma?