Just a bare bakelite board and a bunch of components thrown all over it and bob's your uncle ![Banging Head |O](https://www.eevblog.com/forum/Smileys/default/bangheadonwall.gif.pagespeed.ce.8iLbFYV4Bc.gif)
FYI, that's not bakelite but FR2 or phenolic PCB.
https://db-electronic.com/en/pcb-manufacturing_s35.htm
OK thanks will try and remember it....
1AM, I am going to bed with some sense of satisfaction : I made some progress on the bloody thing !
![Evil >:D](https://www.eevblog.com/forum/Smileys/default/xevil.gif.pagespeed.ic.tdrs7Uj5gu.png)
So as I said I am starting to "study" that "comparator" board (that's how the manual calls it, because well it contains the two required comparators that are needed to do the Voltage / Time conversion ).
I decided to start with the simplest of the problems it has, to wet my feet : the polarity Nixie doesn't light up at all anymore. Circuitry in the top right corner of the schematic posted earlier. Only a couple transistors a few diodes, 2 cathodes... it was a good candidate to get started on that board. Teh easiest to spot / identify on that board, was the 200V supply for the anode of the tube. Bingo... I measure zero volt ! Cool, that means all the circuitry is probably just fine and it's just a power rail missing !
![Cheesy :D](https://www.eevblog.com/forum/Smileys/default/xcheesy.gif.pagespeed.ic.KPzuH4J-TG.png)
The problem was NOT on the board... it was on the back plane / rear board where all the boards attach to with these 12 way card edge connectors.
The socket/female connector, soldered on that back plane, has a bad solder joint. It did NOT look bad at all... I only foudn it because well, I was tracing that rail with the continuity tester, so I quickly found that the joint was not making contact with the pad !
So I wicked that joint completely, and all others on that connector, to see what's what, and look at that ! That joint, and the next 3, did not stick at all to the pad ?! You can see 90% of the pad is still clean bare copper !
![Shocked :o](https://www.eevblog.com/forum/Smileys/default/xshocked.gif.pagespeed.ic.CrwtrNUjLO.png)
The other pads looked OK/ tinned. Crappy PCB back then ? I put lot of flux when soldering back all these joints with fresh solder, hoping it will be good.
So that was it, cracked joint. It must have happened as I plugged and unplugged this board many times when swapping boards, and when I took it apart initially to take pictures.
Thing is, this board has not one but two 10 way connectors, so it takes quite a bit of force to nuplug it. 100% of that force is transfered to those solder joints becasue the connectors are not screwed down/ secured to the PCB. There is zero strain relief so to speak.
So now the polarity Nixie is back to life, look at that ! Even displays negative polarity, so I know the circuitry in there works just fine
![Cool 8)](https://www.eevblog.com/forum/Smileys/default/xcool.gif.pagespeed.ic.cOxV6sPNRd.png)
I do notice however, that the tube looks a bit "foggy", like a car headlight that's got moisture in it from damp weather... well this nixie look a bit like that. Also, at the back of it inside, I can see that scary, horrible... purple glow !! Oh no... it adds up ! This tube really sucked moisture, it's doomed !
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/xfacepalm.gif.pagespeed.ic.EBDwh1hCfo.png)
It's still pretty bright though, but for how long...
I guess I better start searching for a replacement soon, hoping this particular tube model is still available. It reads on it " F9082 ", made in France apparently... can't believe that for one second.
A regular tube might be findable, but this particular one for the polarity and special symbols (odes also the " AC " sign, and also Omega for resistance )... maybe not so easy...
Good night people
![Indifferent :=\](https://www.eevblog.com/forum/Smileys/default/indifferent0023.gif)
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