Heathkit Clock
Glenn wins for most complete documentation of every clock in the house, I would have forgot all the PC clocks myself lol
I built that same Heathkit clock about 40 years ago. Mine is still running just fine, but I did do a preemptive repair on it replacing the electrolytic capacitors before they decided to fail and destroy the clock chip, that IC is make of Unobtanium today... These clocks run a bit warm inside the case so the electrolytic caps will be aging. I'll have to look at the circuit but the clock is getting it's timing from the AC line I'm almost certain. They would likely pick off the 60hz pulses with a capacitor so if that component has changed, it may be the cause of your clocks inability to keep decent time now. Mine has been amazing over all these years.
As for my clocks I have slowly been changing over all radio controlled clocks that sync to WWVB. I love not having to touch the clocks year after year even during the Daylight Savings time changes.