Vintage Nixie Clock Help

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1 week 3 days ago #10546 by dannyv
Came across this vintage nixie clock on ebay. Completely not working.
I bought it hoping to revive. I did get it to work (loose resistor), but now lost on how to completely fix it.

It does seem to function. All buttons in the back working (2 buttons for hours and minutes, one resets to 0 the other advances by 1, and 1 button for seconds to reset, not sure what the switch with red wires does) and time advancing ok, but all nixie tubes are partially lit.
Not sure if that matters, but same digits light up almost the same way. For example 1 lit all the way, 2 will be lit towards the bottom, 5 towards the top, etc.
I do see the board was messed with before and some things were replaced. Looks like a few ICs were replaced, looks like one 7490 IC under the quartz crystal (interestingly the quartz can says 100 Kc on it, guess thats kilocycle an old obsolete way of saying KHz) was removed.
Any ideas where to start looking will be highly appreciated!

Attached are some pics. I don't have any diagrams :(

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1 week 2 days ago #10547 by Ty_Eeberfest
If the tubes are lighting irregularly, partially, dimly, etc. then the first thing to check is the voltage on the tubes' anodes. It should be +170 to +180 DC (referenced to board ground) and if you have a scope it should look like clean DC with minimal ripple. If anode voltage is low or filthy the tubes definitely will not behave well.

If the anode voltage is good you may need to consider the possibility that the tubes are just plain worn out. I take it you don't know any history of that board? I can see it's really old but of course can't see how many hours the tubes have been running.

If the anode voltage is not good then the first thing I'd do is try to trace it back to its source (probably to the area around the transformer) and try to figure out which diodes and capacitors are involved in producing the anode voltage. If there are any electrolytic caps with high voltage ratings they should be viewed with extreme suspicion. Electrolytics don't age well.

Look into it later when the dust is clearing off the crater.

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1 week 2 days ago #10548 by Ty_Eeberfest
BTW - is that big kind of oval aluminum can the 100KHz crystal? It's shaped like a crystal but it's about 10 times the size of any crystal I've ever seen! And I've seen plenty of old crystals - I was modding CB radios in the late '70s B)

Look into it later when the dust is clearing off the crater.

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1 week 2 days ago #10549 by dannyv
Replied by dannyv on topic Vintage Nixie Clock Help
Thanks a lot for the guidance. I'll check the voltage later today.
Regarding capacitors, I don't see any standing out right away besides for 2 tall ones next to the transformer, but they are rated only 10v.
Here are some more pics I could not fit in the original post.

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1 week 2 days ago #10550 by dannyv
Replied by dannyv on topic Vintage Nixie Clock Help
Oh yeah, that huge can the size of a thumb is the crystal.
Says P.B.G. Milano on it, and 100 Kc on top.
Interestingly its not soldered into the board but has 2 little connectors in the board, it unplugs very easily :)
Here are some pictures
Attachments:

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1 week 2 days ago #10551 by dannyv
Replied by dannyv on topic Vintage Nixie Clock Help
Guess what, some search showed this:
www.pbg.it/en/default/25079-0-0/company.aspx

Company still exists and makes quartz crystals to this day :)

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