(Possibly) Zener diode identification.

[Aller]

Hi Everyone. I have a shorted diode marked 15A 435. It's most likely a Zener, considering its place in the circuit and that it was connected with the anode to the ground. I tried to find its reverse voltage value on the internet without success. Can anybody help? This board is a part of the Caterpillar control system. The board number is CAT 106-1154. Does anybody have any insight on this board?  The board doesn't have any designators; in fact, it doesn't have any silk screen. The only symbols (generic diode and the "+" signs next to capacitors) are etched from the copper plane and are (I feel) for polarity only rather than any specific markings. Pictures attached. The diode's very bad quality (dark) photos are due to the barely readable markings, so I had to play with lighting under the microscope to show anything.

[fzabkar]

It's probably a 15V unidirectional TVS diode, something like a P6KE15A.

[MathWizard]

Is that a SMPS there on the right, that transformer and diodes and mosfets, and a controller chip?

In computer SMPS, I've seen a lot of 18 and 36V protection zeners in gate drive circuits, auxiliary low voltage windings, and some of the sensing circuits. But there's also reverse polarity diodes around some of the main transformer windings.