Yeah, it seems the selftest is nice but doesn't really pinpoint the area or traces one needs to be concerned about.
It does seem the 16750s have a JTAG connector right next to one of the FPGAs close to the backplane connector.
I measured the connections and it seems the connections are indeed JTAG (haven't verified yet need datasheets), but I couldnt find any further connections for a JTAG chain. Maybe thats done differently.
The mainframe must be able to reprogram the cards and the source files are in Logic Analyzers Software directory (ttf / rbt / bit / xsvf files for various cards Fatcat (16910) / Fastcat (?) / Wildcat (16950 also likely 16753/54/55) and 1696x as far as I could identify).
There are others: Yari and Daytona that also come with a suffix Pv (= Performance Verification)
Daytona maybe 16760A but there are two revisions
Yari = 16750A/51A/52A
Yari Rev 2 probably = 16740A/41A/42A/50/B/51B/52B (could be verified by modifying the resistor field accordingly 4xA <-> 5xB ) See
https://www.eevblog.com/forum/testgear/hpagilent-1675x-logic-analyzer-card-memory-up-hack/agYariMemFpga.rbt is most likely for the 4 memory controllers in the middle of the card. The files are even humanreadable (well semi: 0s and 1s

agYariIfaceFpga.ttf is most likely for the Flex 10K10 (15 KB * 4 for plaintext encoding,only sram (=no persistence), there are no configuration devices on the board)
What about the rest?
I couldn't find a file for the EPM7256A so that is probably programmed via the JTAG connector in the factory. This most likely determines the basic identity of the card (Family / ID Code), the resistors determine the exact model/options.
It is probable that the EPM7256A then routes information from the backplane to program the Flex 10K10 (most likely interface logic to read out the memory) and the FPGAs on board (memory controllers, the 4 silver chips in the middle for 16750A), the two Chips with heatsinks are probably also ASICs as there are no files to program them. Then ASICs for FISO maybe A/D maybe Zoom (5 on the 16750) and last not least programmable comparators (4 top / 4 bottom).
There is an additional TTL to BTL transceiver TI FB2040 close to the backplane connector (for what?)
There is an PCF8584 close to the JTAG connector, but not connected to it -> Probe identification?
Has anybody ever tried JTAG and got it working?
Then a boundary scan would be possible making life easier.
P.S. Sorry if this post looks weird, work in progress. Help is welcome, maybe you can answer one of the questions?