Hi Ray,

Thanks for the tips.

I started with step 1 and found that the resistance between VIN and GND was low, ~4 ohms. I removed IC1, then started taking components off. When I took the zener diode D3 off, the resistance went up to around 80 ohms. So I continued taking things off. I took IC2 off, C2 then D2. At each step I started to notice that it depended on the mutlimeter’s polarity as to whether I’d get the 80 ohm reading or not. After taking D2 off I got a high resistance. Then it dawned on me that the polarity probably does matter on the multimeter since we’re checking a diode. Anyways, 80 ohms also seems too high to me for D2 but I don’t really know much about Schotky Diodes… or maybe my mutlimeter isn’t effective at measuring it.

So I checked the zener off the circuit board and it measures ~2 ohms in both polarities so I think that is definitely shot.

I believe the root cause to be a small wire clipping from one of the other components that was sitting on the top side of the board which I noticed after the first power on. It was near the 24 vac components so could have shorted something.

I’ll send a PM requesting some replacement parts.