On Monday, July 8, 2019 at 6:28:43 PM UTC-4, HW wrote:
On Mon, 8 Jul 2019 11:30:50 -0700 (PDT), John-Del
wrote:

I would have bet almost anything the mosfet is shorted. Put it on an ohmmeter and check for continuity across all the pins.

The transistor responds just as it should to the ohmmeter. I have not
tested it at high voltage or current.


My first rule of repair is that you'll never see everything in your career. In 50 years, I have seen just one high voltage high current semiconductor check normally on an ohmmeter but "short" under circuit conditions, then check normally again on the meter. They generally do you a favor and short themselves silly. The one I did find was an early 1980s RCA TV where the horizontal/hv output transistor would go into full conduction with *any* dc on the base and blow the fuse. It checked fine out of circuit but a new one stopped the immediate and spectacular blowing of the fuse. That's the only one I ever saw.

So, while you wait for your parts to come in, follow Peter's advice and check every diode you find in the circuit as that's the next part failure percentage-wise that follows your kind of failure. Often, a zener will check OK front to back but will conduct significantly off it's printed voltage (generally lower). Also carefully check all low value resistors.