Subject: Re: HP nixie tube module information needed

From: "Dwight K. Elvey" <[email-masked]>
Date: Tue May 20 16:39:01 2003

>From: "Tom Uban" <[email-masked]>
>
>Hello,
>
>Probably my best find at the recent Hamvention in Dayton OH was a
>stack of nixie tube modules made by HP. In retrospect, I wish that
>I had purchased the whole box of them, but I hopefully have enough
>to at least make a clock.
>
>I have two variations on the modules, the part numbers are:
>	HP 05212-6016 series 648
>	HP 05212-6003 series 415
>They both use Borroughs B422 nixie tubes and look like they may have
>an integrated HV supply of some sort.

Hi
 I don't see anything that I'd call a power supply. The
transistors look like they might be flops/latches or buffers to
drive the nixies. If you don't find some schematics, you
could hand draw some. I doubt that it would be too hard to
follow.
Dwight

>
>Here are a couple of pics for reference:
>
>http://www.ubanproductions.com/Images/nixie1.jpg
>http://www.ubanproductions.com/Images/nixie2.jpg
>
>I would appreciate if anyone can tell me what HP (or other) instruments
>may have used these modules. I would also like to find a schematic of
>the module if possible.
>
>Thanks!
>
>--tom

---

From: Tom Uban <[email-masked]>
Date: Tue May 20 17:04:01 2003

Dwight,

The circuit board portion is easy, but the bit inside of the black
box is a bit more complex. While I originally thought that it might be
an integral HV supply of some sort, I now have additional information
which says otherwise. Interestingly enough, that info originated from
Tony Duel. Here it is:

     HP made a decade counter/display board where the counter FFs were
     made from pairs of transistors in the conventional way (8 transistors
     on the board). These were controlled with diodes to count in 1242
     (not 1248) BCD code.

     The outputs of these counters drove 8 neon bulbs, and by varying the
     bias applied, the state of the counter could be latched in the bulbs
     (that's why this is relevant here). These bulbs were mounted inside a
     plastic block on the PCB, and shone onto a think-flim circuit of CdS
     photoresistors. These were connected to form a binary to decimal
     decoder to drive a nixie tube.

--tom

---

From: Joe <[email-masked]>
Date: Tue May 20 17:38:00 2003

>     on the board). These were controlled with diodes to count in 1242

    That makes sense. Before HP-IB HP used a BCD interface. It wasn't a 1 2
4 8 code, it was a 1 2 not2 4 or something like that and it was designed so
that there were no possible states greater than 9. Data was sent 4 bits
parallel, nibble serial fashion. I don't remember exactly how but the was
also a way to handle +/- signs and decimal points.

    Joe

---

From: Joe <[email-masked]>
Date: Tue May 20 17:39:39 2003

Joe

---

From: [email-masked] (Tony Duell)
Date: Tue May 20 19:32:54 2003

> which says otherwise. Interestingly enough, that info originated from

Yes, it is me :-)

The block is not that complex. Inside there are 8 neons. From the top, 
they are : C, C/, B/, B, D, D/, A, A/ (according to the manual). The neon 
wires are soldered to the PCB. On top of the block is the thick-film LDR 
array, and on tom of that is a resistor network of 10 270k resistors. The 
top wire of that goes to the +20V rail, the wires on the left go to the 
nixie cathodes (there's a 270k resistor from each cathode to +20V). The 
LDRs also connect to the cathodes. The bottom wire from the resistor 
network is not used, but the pin it's connected to is the common of the 
LDR array, and goes to -130V.

There's a good theory-of-operation section in the 5245 manual, BTW. You 
want to try to get a copy of this.

-tony