Digital Clock

My oldest surviving project from 1973


          I worked in RCA in Harrison NJ. It was a tube company! New Jersey Unemployment put me there! Great pay but it was all old technology. At home I kept on turning out solid state projects. RCA had a clock with over 20 IC in it. Some were even DTL! I built the RCA clock from scratch using RCA readouts. I kept it on my bench at work so we all knew the time.

          At that time Poly-Paks and Radio Shack started selling clock chips. The Engineer in my area wanted to get the old technicians interested in digital circuits. Somehow I ended up getting the parts for the old farts. I helped one or two with their clock while the engineer helped the rest.

         You have to picture this! I am supplying the parts and help. At some point one of the old guys says lets have a contest to see who can build it the smalest. The guy had the Engineer helping him. The day of the contest they are all razzing me! Nobody sees the bulge in my pocket. The moment comes when the Engineer is going to do the judging. I let them ride me a little more! I then pull it out of my pants and pluged it in! I said nothing until today! 42 years later. LOL

          RCA was closing down and I got the AX. I took home the RCA clock I built. It used display tubes never sold to the public. I got a job at Radio Shack. I put the clock on a shelf at the store. Some kid got me to sell it to him. After working at RCA I had a hard time finding a job. When people would see my work history they would say "RCA, as in Tubes?"

         So I went looking to go back to school. The people at one school were laughing at me because I went to RETS in Nutley. A guy there took me to a room to show me what his best student built. There it was MY RCA CLOCK that I sold to that kid who came into the Radio Shack. I was loud and a second instructor came into the room. He knew me from the Radio Shack store and he admitted the clock looked familiar. The clock used RCA Doorknob Numitrons mounted in a custom bracket made by my dad. There is no way it wasn't my clock. I just walked out of there!!! I got a job at TRW a few weeks later without the schooling.

Back of clock

          The clock uses a Mostek 50250 chip.I used a reed relay to sent AC voltage to a relay to make the alarm buzzing noise. If you use the DC to run a buzzer the spikes mess up the circuit.The top button is the snooze button. There is a three way toggle switch for Time, Alarm Time and Alarm Time set. Notice those side slots. There are three boards that slide into them. Two driver boards full of transistor drivers and the power supply. Those old men came up with all kinds of lame remarks! The parade of Engineers from other departments was hilarious. Several Engineers noticed the slide rack system. The racks are held in with double sticky tape. They were custom made by my father at Resistoflex to my specification.

Inside of the clock

Email: John a quick question

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