Kukoke Outlet Timer: Over-powered Zener Diode

If the title seems familiar, it’s because there’s no visible difference (apart from the “brand name”) between the Enover timer that failed a little over a year ago and the Kuoke timer that recently failed:

Kukoke timer - overview
Kukoke timer – overview

That’s what it looked like after the repair. Prior to that, it’s just a blank display with no response to any inputs.

Given identical hardware, the overheated phenolic PCB under the Zener diode came as no surprise:

Kukoke timer - zener heat death
Kukoke timer – zener heat death

As promised, though, this time I epoxied a brass shim heatsink to the new diode in hopes of cooling it enough to live long and prosper:

Kukoke timer - zener heatsink
Kukoke timer – zener heatsink

I suppose I must now preemptively affix heatsinks in the two surviving timers, because we all know how their stories will end.