Bart:
The problem would seem to located in the controller board.
Many of these are multi-layer boards. I have had some luck
with resoldering the whole board, even the solder-thru holes
where possible. Must have been an inter-layer break.

Some of the older LCD's used a lot of surface mounted
electrolytic capacitors, which were always going high ESR.
I could not get the manufacturer to sell me any of these boards.
Good luck..
John