Interesting update - I tried probing a bunch of pins with my Z0 probe (simply because it's input is 1K to GND). I didn't find much interesting, EXCEPT that probing pin 135 on the FLEX chip causes things to sorta work (either side of the resistor). See attached screenshot. I say "sorta", because the frequency is still wrong, but I consistently see signals on all the pins that have signals, and I never get the error about the WRAP flag.
Also, when probing that pin, self-test actually passes the zoomChipSelTest... though fails the zoomAcqTest. But, the only failure it gets on the zoomAcqTest is the edgeCount (no errors about FISO stuck bits), which maybe makes sense, since the output frequency I was seeing didn't match the actual input frequency.
pv> x zoomChipSelTest
Slot E: Filling FISOs for Pods #1 with zeroes...
Slot E: Checking FISO #4...
Slot E: Checking FISO #3...
Slot E: Checking FISO #2...
Slot E: Checking FISO #1...
Slot E: Checking FISO #0...
Slot E: Filling FISOs for Pods #2 with zeroes...
Slot E: Checking FISO #4...
Slot E: Checking FISO #3...
Slot E: Checking FISO #2...
Slot E: Checking FISO #1...
Slot E: Checking FISO #0...
Slot E: Filling FISOs for Pods #3 with zeroes...
Slot E: Checking FISO #4...
Slot E: Checking FISO #3...
Slot E: Checking FISO #2...
Slot E: Checking FISO #1...
Slot E: Checking FISO #0...
Slot E: Filling FISOs for Pods #4 with zeroes...
Slot E: Checking FISO #4...
Slot E: Checking FISO #3...
Slot E: Checking FISO #2...
Slot E: Checking FISO #1...
Slot E: Checking FISO #0...
Mod E: TEST passed # "zoomChipSelTest" (13, 5, 1)
pv> x zoomAcqTest
Slot E: Chip9: edgeCount=2570, exp=811
> Slot E: Chip9: Zoom Acquisition Data Frequency Test Failed!
Slot E: Chip8: edgeCount=2570, exp=811
> Slot E: Chip8: Zoom Acquisition Data Frequency Test Failed!
Mod E: TEST FAILED # "zoomAcqTest" (7, 7, -1)
Do you happen to know anything about this pin? It looks like it goes to an inner layer, and haven't had a chance to track down where it ends up yet. But suspiciously, it's right next to pin 136-138, which earlier you said are some Zoom chip select pins.
BUT, something else that's interesting... I did the exact same test on my working 16750A, and got the exact same result (same pins showed activity at the faster than actual rate). So, hopefully this pin provides some clues, but maybe it actually leads nowhere. :-/
Thanks,
DogP