Mysterious single-digit LED clock kit from 1979

[@JIMO415]

Wow, nice find. That looks perfect in that shadow box. I wonder if there is enough voltage headroom with using the 9vac power adapter and expecting the 7812 to work as intended....not that this circuit needs a tightly regulated supply tho. Cool. Enjoy!

[@GeigerCounterVirtualMuseum]

Now that’s interesting!

[@50sTransistorRadios]

Thanks!

[@JohnnyX50]

I found a stack of single digit led boards in trash near a bingo place. They use the same layout of red leds for 7 seg digits and controlled by 50-Logic series. There was a controller board with them but no way of knowing how to use it but I can inject binary into the digits to make numbers and I was going to make a clock out of them lol I think they were the prize board at some time as there is also a £ symbol and a P. There is a black front cover on them that the LEDS just poke through. This thing you have looks very similar so maybe same era :D Nice find :D It looks hand made, as in, we used to make pcbs like that in electronics workshop in the 1990's on my YTS scheme! :D

[@50sTransistorRadios]

Thanks! It sounds like you could make quite a clock out of those boards, though if they are each as big as this single board, you will need quite a big case. The PCB is single-sided, and if not for the stamped 1 in a triangle on the back, I would guess it had been homemade. It may well have been made in a small shop though.

[@JohnnyX50]

@@50sTransistorRadios Your board may have been a project from a magazine or indeed purpose built. I found the boards of mine just now in the attic lol. The boards of mine are built by a ECM Systems and stamped 9-6-88. A quick look on google does indeed label them as Bingo and Entertainment equipment suppliers! It looks like the boards were designed to run off 24 volt with a power plug and interface on the back which is just a 14 pin IC socket. The pins are labelled AC(T)AC(U)BD(T)BD(U) GND suggesting BCD input to 2 independent digits. The other ICs are all DIL or SIL resistor packages, a voltage regulator, a few caps, a fuse and 2 TC4511BP chips. The led layout is identical to yours with 5 leds per segment but maybe only about 3-4 inches in digit length and about 2 inches wide with the board only being slightly bigger. Id say total size including black wood cover with holes in is about 7inch wide by maybe 5 long. I still have the divider/oscillator to make 1 sec pulse on a breadboard, all the logic AND gate chips, Binary counter chips, practically everything to make it work but just never got round to doing it lol. All the leds are squashed so I need to carefully straighten them out one day and maybe finish it. Your device is very interesting as the MM518N is designed to display a clock on a TV screen in conjunction with an MM5841 chip! :D so some serious weirdness is going on to display a single digit clock like that :D I just love the old way of doing things, you learn a lot more about circuit design, logic and control by DOING rather than just sticking in a PIC or Arduino and copying someone else's code, no fun at all! Very nice board and I'm glad you got it working, should last for years!

[@misterhat5823]

RCA was the inventor of 4000 series logic. But they haven't made ICs for decades. That RCA labeled CD4051 has to be original.

[@50sTransistorRadios]

Yes, the CD4051 is likely original. The CD4040BE with the 1996 date code is the one I'm pretty sure is a replacement.