Assembled PCBs

A project log for TTL binary clock

A binary clock made from TTL chips from the 70s and 80s

Ken YapKen Yap 11/14/2019 at 22:200 Comments

I got the PCBs a while back from a recent Elecrow offer. I ordered 5 PCBs and was delivered 7. Hope I have enough old TTL chips to populate them all. The power is supplied from a 5V phone charger via this micro USB socket.

I populated a couple of boards. I soldered LEDs to one and powered it on. The copper pillars are to hold the board a certain distance above the table while I soldered the LEDs in so that they would all be the same height above the board.

Unfortunately while the counters work correctly, the 1 Hz LED sometimes blinks erratically, with spurious pulses, which cause the counters to speed up. Have to bring out the DSO to see where the extra pulses are coming from.

I also noted that I have to use a decent micro USB cable, the voltage drop across cheap ones is significant.

Edit: A few minutes later: Now the clock has settled and the 1 Hz LED is blinking at a steady rate. I hate it when circuits "fix themselves" like that. I'll leave it running to see if the glitch has gone for good. Probably not. 😿