Hello Dave,
Nice optimizations and tricks in your clock
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)
For the hour counting, I would have used half a 4520 wired as modulo 12 counter, and a similar bit of glue logic to convert that to the needed 1,5 digit signals...
This way you could replace the 4013 used for the AM/PM by the second half of that 4520 (with no reset, just use the LSB and let it count modulo 16) -> spare one IC.
Or in fact, I would in fact have made a 24 hour clock, as this format is more common here than AM/PM...
When I was young, I made a LED clock with a bunch of leds arranged in two concentric rings.
I also brought it to school, and no one freaked out.
It was made on two self made PCBs with hand drawn traces + decals directly on copper clad ..... Wow, when I think about that .....
The design came from a elektor or elex.
Elex was a very very funny electronics magazine with a lot of funny illustrations :
look at p4/5 here for a nice story how 7 segment displays are organized
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)
)) :
http://docsenstock.free.fr/a/elex/LX1989-13+.pdf(yeah it's french, but you will understand the story from the pictures anyway.)
Wanted : complete scans of the "Elex" magazines ....
At the lab I've never had a single blackout (don't know about nights when not here)
Your clock has a nice side effect feature of detecting power losses in the night by resetting
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)
Blah, it uses one of those new-fangled integrated clock chips, sacrilege!
Yep, that IC is definitely not in production any more, whereas all the logic IC you used can be bought for 10-50cent today.
a genius bomb-maker who goes to the extreme of reverse engineering a fucking radio alarm clock instead of going with a much simpler 555 timer or Arduino or the good old mechanical switch
A 555 is not a good idea for a bomb timer, or any similar long timing : at long times it becomes unreliable because of the leakage current overcoming the capacitive charge current.
I suggest using a 4060 with a much faster oscillator and a big division factor instead.