B&F Enterprises "Digital Clock" flakes out

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7 years 5 months ago - 7 years 5 months ago #4792 by Dr. Optigan
Hello, everyone. I've had this vintage nixie clock in my possession for several years now. It was sold as a kit by a company called "B&F Enterprises" in the early 1970s, and uses ZM1000R tubes. Here is a photo of it:



I'm not entirely sure what sort of design it uses, but it seems to be based around 74xx ICs, and a friend of mine believes that it's likely based on a design published in Popular Electronics magazine back in the early '70s. Some of the ICs have mid 1972 date codes on them, though several were replaced in the mid-late '80s. When I first purchased it, plugging it in resulted in the clock running for about three seconds, after which the main fuse blew.



This past week, I finally got around to replacing the filter capacitors (located along the back of the case) with modern electrolytic capacitors, but the fuse still blew. A friend of mine then took a look at it, and after much trial-and-error, replaced two diodes in the HV supply that at first looked to be OK, and the fuse stopped blowing. The LV supply seemed to be a bit low to him, but the clock seemed to be running otherwise, so he buttoned it back up.



Once I got it home, I plugged it in, and set the time, after which it kept accurate time for over 18 hours. Unfortunately, it soon started glitching up, in that the time started jumping all over the place, and the minutes tens digit would intermittently fail to light. Any idea what might cause a problem like this with a TTL nixie clock? My guess is that it might have to do with sockets (more like individual pin-holders) which the ICs are plugged into; at one point during the troubleshooting, the minutes would not advance, and re-seating some of the chips solved the problem. Might the 'low' 5V supply be an issue as well? Thanks in advance!
-Adam
Last edit: 7 years 5 months ago by Dr. Optigan.

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7 years 5 months ago - 7 years 5 months ago #4795 by Dr. Optigan
UPDATE:

I don't think the problem is due to the low voltage power supply not being able to supply enough power. I connected the clock to a variable AC supply, and turned down the voltage to see what would happen. The nixie tubes dimmed, but the number count didn't glitch. Even when I turned down the voltage enough to cause the tubes to go out altogether, the most that happened was that the seconds count stopped entirely. This would seem to point towards some sort of issue with the IC sockets, though I'm not entirely sure. Once again, any ideas? Thanks!
-Adam

PS: All of the pics in the above post are from when I first got the clock, before I replaced the filter capacitors. I'll soon be taking some new pictures, including ones of the clock running.
Last edit: 7 years 5 months ago by Dr. Optigan.

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7 years 5 months ago #4805 by Pacman223
That's a cool clock, was it very expensive new? I don't know that I have seen pictures of Nixie clocks from that far back. I always thought Nixie tubes at that time, cost to much to use them in a clock.

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7 years 5 months ago #4808 by Dr. Optigan

Pacman223 wrote: That's a cool clock, was it very expensive new? I don't know that I have seen pictures of Nixie clocks from that far back. I always thought Nixie tubes at that time, cost to much to use them in a clock.


B&F Enterprises used to advertise in the back of Popular Electronics and other magazines.. I think they'd gotten a really good deal on nixie tubes, and started to sell digital clock kits like this one. Pretty sure it wasn't particularly expensive, and it shows in the quality of the circuit board they used. Anyway, here's one of their ads:

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7 years 5 months ago #4809 by Pacman223
That's very cool. I bet this was one of the first digital clocks a normal person could buy.

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7 years 5 months ago #4813 by Dr. Optigan

Pacman223 wrote: That's very cool. I bet this was one of the first digital clocks a normal person could buy.


Well, for electronics hobbyists, anyway. The early '70s was when digital clocks were starting to become accessible component-wise. Integrated circuit technology was starting to become cheaper, and companies like B&F Enterprises were offering (relative) bargains on display tubes (LED technology was still in its infancy, but picking up speed rapidly). Here is a photo of another early nixie tube clock I have, hand-wired using perfboard:


(Unfortunately, someone stripped the power transformer from it at some time; I'll have to make another thread about it at some point)

Popular Electronics and other magazines started publishing various designs for digital clocks, such as the "Digi-Vista" ( 4-digit and 6-digit versions). Soon, entire kits were offered by the likes of B&F Enterprises and, of course, Heathkit . Around this time, companies began offering various different "clock-on-a-chip" ICs , like National Semiconductor's MM53xx series.

In the mid-late '70s, fully-assembled digital clocks became commercially viable through the use of both multi-digit vacuum fluorescent displays, and the maturation of LED display technology, which was much easier (read: cheaper) to drive than neon or incandescent display tubes. Hobbyist building of digital clocks started to fall by the wayside around that time, though some interesting project articles appeared from time to time, such as the Skitronix Hyperclock . Nowadays, improved microcontroller technology has led to new and varied custom clock circuit designs, including ones using the good ol' numerical display tubes we know and love. :)

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