jhalphen , what is the origin of the photo you provided in post 167? I mistakenly assumed that was your collection.
Never found any schematics, after trying to contact sony america and sony japan. May have also contacted sony singapore. There was likely some update/revision support so the service manuals must exist somehwhere. I search on japanese hobbyist sites sometimes , but have mostly just done repairs by repairing capacitor corroded trace, and looking at IC white pages and other service manuals for unilink devices from the time to try figure out how use the displays with no diversity unit present.
The cable that I found to be modifiable for test purposes is listed on ebay as Female MDR - Female MDR Camera Link Cable Frame Grabber Communications AIA
screenshot supplied
It does not have sufficient depth to make contact when the unit housing are on, or retaining tabs, so is it only suitable for testing with both display and diversity unit housings removed.
Will post the pinouts of the 26 pin connectors after determining if functionality is the same across all 3 models.
Been spending most focus on the xav-55n, as that extra power harness that allows for power up functionality with no diversity unit required, but no menu without the diversity unit. Also, the masking on the front bezel of the xav-u51 lacks the "diversity" mention as does the xav-55n, but lacks the extra harness present on the xav-55n. Having them all in a row on the bench will hopefully accelerate the fixes.
Also, just a weird UX note. The physical menu illumination has a choice of color between amber and green. Quirky.
edit. image as attachment is poor quality
double edit: archived JIC
https://web.archive.org/web/20230117...m/121905099223
shameful triple edit: I just reread this multiple times because something looked off. The ebay listing mentions "11 shielded pairs". I don't recall that from when I purchased. I assume It would mean 22 of the 26 pins are shielded in a 26 pin cable, but one should specifically ask to make sure any cable received will be a 26 pin connector, just in case anything has changed. Also to make clear, there is no mirroring, the pinoutput and pininput of the double female mdr is the same as the sony cable for these indextrons. The difference is that 1-4 and 14-17 are bridged in the original cable, where all pins are individually connected in the MDR. This does not change functionality, as 1-4 is reserved for relayed 12v, and 14-17 is reserved for ground.