It is very possible you have a bad circuit board. Odds are it is the front AC board due to it went blank but the rear worked. But NOT 2 boards with the same identical problem. If it was me and you were at my shop, I would replace ALL the RG 11 connectors, then test. Did you look inside the quick connect off white junction boxes for corrosion?
Also, what YOU can do, is, swap the front and rear AC boards. See what happens. 99% of the time it is the Com Cable/s or connections when you have loss of display or communication. Doug
PS, DISCONNECT the rear to front Com cable at the front AC and see what happens. This removes a possible dirty signal from the rear area ac and cable