The top two AN displays work fine but the bottom two got nothing. I've reflowed all the headers and tested that the ribbon cable and MPU are good by using a rottendog replacement display (all four work fine on that one).

Is there a single part they have in common that might cause both to be dead? Looking at the 4050 or 7180 chips, perhaps? Nothing physically damaged on the board (no toasted resistors, etc.)

Be gentle - primarily a vid guy here!

TIA

Williams System 11.

F-14 Tomcat.

Bueller?
Bueller??
Bueller???

Thanks.

Well, the top two work fine, that alphanumeric ones. The bottom two, just the numeric, are dead.

Looks from the schems that the AN and N displays do have different pinouts, so swapping an upper and lower for troubleshooting purposes is out.

I've got some 7180 on the way. Will update then.

Piggybacking all the 7180 changed nothing. Last ditch effort will be testing the resistors 14, 15, 16 and 17 out of circuit.

No go on any of that. Guessing the bottom two are gassed. The top two are getting =/- 85v as are the bottom two, so they all should at least show something at this point.