Some sleep and I am functional again ! So let's see what was in that box
Grab a pint of tea and a couple packets of your favorite biscuits
It's....a nice boat anchor ! Well it's not that heavy.. 17kg according to the manual, though I don't know it's that dry weight or not...
I can't afford to import a fancy HP 8 nixie counter, probably never will, but I found the next best thing ! A French equivalent... a Ferisol type HA300B.
'60s design, full width, looking rugged and indestructible, all discrete transistor design, 50MHz (given for 51MHz actually... marketing at play I guess...), 8 Nixie tubes, a main frame with a plug-in on the right side, and a ton of plug-in boards inside.
It is just like the old HP... but it's a Ferisol. Actually it means more to me, begin a defunct French company, so quite exotic and rare of course, being a local product, and such low volume, compared to a "mundane" easy to get (just click 'Buy' on Ebay and pay the money). So preserving this piece is even more essential I find, and I am that much more happy to have it.
Power socket : has the weirdest socket I have ever seen, for sure ! It's not even a "consumer" type socket ! Plus, it's PROTRUDING instead of being recessed ! Might be why they added handle bars at the back as well.. to protect this connector somewhat. See picture below. It's round, protruding a lot, and has a bayonet style locking mechanism. Yes, I told you it was weird, didn't I...
Luckily the seller supplied the power cord to go with it !!!
The service manual told me all about this connector, luckily : it's made by some company by the name of " SOCAPEX ", whoever they are. Model number for the socket is FFC23AL and for the plug it's EM23AL.
That's far more interesting than the usual HP counter, many of us have.
Possibly the first time I've seen those neon trigger tubes in a counter, the early Anita calculators used them as ring counters, but not sure this is the case here.
What intrigued me when I first saw them, is that they have 4 terminals... so clearly they must some exotic/special purpose kind of bulb...
Looked them up in the schematics, see below. Looks like they are used a switch to drive the HV to light up the Nixie digits.
Schematic shows the pinout for them. Looks like there an anode and cathode.. of course, but also a pin called ' St ' near the cathode, and another one near the anode this time, called ' Pr ' which it says, means ' Pre-ionization '.... good luck with that.
Manual calls this curios bulb a " Thyratron ", there you go ! I guess it does not translate...
Model :
Z70UWhat I suspect though, but not quite clear not even when reading the theory of operation section.... is that these bulbs have a dual purpose. They drive the Nixies but I suspect they might as well have some tricks up their sleeve that allows them to implement the latching of the display / data.... but need to study the manual more to be sure... but it's a strong suspicion.
That would make sense, as the symptoms for my 3 defective Nixie tubes seem to be a combination of driving and storage/latching. If one of these bulbs is defective, the chances of finding new ones for sale is... well is not great I would imagine !!
Of interest, I note that there are only 7 bulbs, not 10.... so how can you drive the 10 digits in the Nixie tube ??
Found the answer in the theory of operation, see below. Looks like the Nixie tube they use, a "
ZM 1032 " is wired internally with some multiplexing... instead of having just a common anode and a cathode for each of the 10 digits, you have TWO anodes and 5 cathodes. There is anode common to the 5 'odd' digits, and another anode common to the 5 ' even ' digits.
This way you need only 5+2 lines to drive the tube, instead of 10+1 . Well I don't know if that's the reason... I doubt it, as tehre is plenty of PCB real estate to add the extra lines for a more traditional non multiplexed. I suspect the reason is probably more to do that the less lines you have, the less components you need. So cheaper and more compact board, more space in the instrument to implement more features or refine existing features. I don't know....
I've seen that connector before, believe it or not we had some at work, so something British Rail once used them. Can't remember if there was any left in the surplus stuff I acquired.
David
My old friend got back to me about that. He says he has many other instruments of that era, from Adret for example, that used that connectors for power... go figure.
He told me the original manufacturer 80 years ago was ' FRB ', then Socapex in the '60's, then today made by " HyperTac ".
Searching for ' FRB connectors ' on Ebay was successful. Both the plug
https://www.ebay.fr/itm/313500692435?hash=item48fe18efd3:g:tBAAAOSwnt5gedAH...and socket are available. About 10/12 Euros each.
https://www.ebay.fr/itm/312857891583?hash=item48d7c892ff:g:ks8AAOSwoC9d2Qez... or a bundle with a plug + socket, 20 Euros shipped... am tempted, a spare can't hurt...
https://www.ebay.fr/itm/312858224844?hash=item48d7cda8cc:g:z3IAAOSwoaNd2TCgThere is even a NIB old one, a plug, with all its accessories...
https://www.ebay.fr/itm/312858214400?hash=item48d7cd8000:g:lv0AAOSwFhZd2S-d