4017 Decade Logic Clock

I just assembled another prototype of the clock, this time it worked nearly perfectly. I think I had some older vintage 4017 counters that worked on my breadboard, and the newer ones I used on the PCB version didn't work. I was able to replicate the problem on my breadboard, and I made it work after I changed a few pull-down resistors to a much higher impedance. I also realized the PCB was missing the 11 o'clock hour, and i solved this by removing the zener diode and capacitor on the hours segment. I changed all the zener diodes from 4.1V to 3.9 volts, I think the newer vintage 4017's were to blame for the difference. The tens digits weren't resetting to zero and switching to 3.9V zeners fixed it. I also changed the USB power plug to a USB B plug because it's through hole, and USB B cables are really easy to find. I changed the LED current limiting resistors to resistor networks just to save a few solder points, because it's seriously a lot of soldering! My next step is to get my hands on a really nice oscilloscope to fine tune the capacitors that make the crystal oscillate, and I'll be making yet another PCB before I call it finished. I'm also working on getting my hands on a flatbed inkjet printer so that I can print some cool art on the circuit board instead of being limited to just one silkscreen color. I'm imagining a matrix themed background of green 1's and 0's.

I just finished assembling my latest PCB and found that I t still wasn't quite working perfectly. I found that I was missing two key resistors in my schematic that I had on my breadboard, and the hours still wouldn't advance. So I've added the two resistors. and I found that I had an error with U1 (Hours ones) not advancing U2 (hours 10's.) It works perfectly on my breadboard but I was using a pair of 2n3904 NPN transistors to form an AND gate instead of the AND gate on the schematic. I think everything should work at this point.

This clock is nearly working. I soldered together the latest PCB, and it works pretty well except the seconds wouldn't advance the minutes, and the minutes wouldn't advance the hours. Long story short, I solved this by replacing a few 1n4148 diodes with some 4.3V zener diodes, and added a few small caps. if you build it on your breadboard, I won't say it will be easy but it should work!

Based on your feedback, (thank you!) I've uploaded the schematic diagram of this clock. If you'd like to try building it on your breadboard, it should work. Thank you!