Based on reading other threads, I've tried the following:
Disconnect everything but the CPU from motherboard. Remove RAM modules, GPU, etc. Try to power up. Same situation.
Revisited the PSU test. Disconnected PSU and plugged in the test jumper. Can feel air moving at the back of power supply grill, so apparently, though silent, it IS running. Of course that does not mean the rails are good.
Took out CPU and reseated CPU and cooler assembly. Retested. Same result. The fans pulse for 0.5 second and then stop.
Not sure at this point if it's the PSU or motherboard that's defective.
Out of desparation, I tried jumpering the green and black wire (3&4) on the 24 pin connector. This enabled the power to come on and stay on. However, still no output from either the motherboard displayport or the GPU displayport. Seems like power supply is operational, but no POST from motherboard.
Regards,
Mark
...
"If it doesn't cause an earthquake, you need a bigger subwoofer."