[Elecraft] Protective zener diode failure

[David Olean]

I have a K3 and for the second time, the protective zener diode has shorted out for no apparent reason. The first time, I sent it back under warranty, but I was charged for the repair. It died again today with the voltage set at 12.4 vdc at the power supply, (an Acopian commercial rack mount unit)  In each case the radio was not being used. It was just sitting there with power applied. Does this happen often?  Anyone else suffer similar events? I had another K3 hooked up at the same time that did not die.  I am at a loss as to why it happens to the same rig. There were no thunderstorms in the area. The power supply still is delivering 12.4 volts.

73
Dave K1WHS