A little tester to determine transformer PhaseDots with no scope or signal generator

I built one of these nice little testers and installed it into a small chassis box. It appears to correctly identify phase dot winding ends, but the red LED doesn't light up when connected in the reverse position on the windings. The LED does function properly with a voltage applied and is connected properly to the board, but no red light. I'm not savvy enough to troubleshoot CMOS circuits. Does anyone have some suggestions on how to correct this?
Thanks very much, and thank you Mark for a nice little device!
 
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Snap oscilloscope photos of nodes XOR, XNOR, GATE1, and GATE2. Do it twice, once in each of the two orientations of the windings.

XOR_test1 should match XNOR_test2 and XOR_test2 should match XNOR_test1.

GATE1_test1 should match GATE2_test2 and GATE1_test2 should match GATE2_test1.

If they don't match, aha, you know where to investigate.

There's a chance you've got a bad solder joint or bad component in the vicinity of the MOSFETs and Schottky diodes. I'll be away from DIYA for several days and not browsing.


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Hi Mark,
I tested as you advised and here are the 'scope shots. First image is in phase, the second is out of phase.
Then I resoldered all joints, and re-tested the transformer, but still the red LED doesn't light when the transformer is out of phase. Then I tested all diodes and resistors, and the MOSFETS and they test good.
The red LED lights up in diode test mode with my DMM (even brighter than the green LED) and it's wired in correct polarity, so I'm still on the hunt.
Cheers,
Greg
 

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