Hi,
i have exact the same issue, i replaced the Ic with a AT89c51RC2 with the Firmware n80c51bh_E3633A_Display_Board from a nice member here in the forum (thank you for the file) , the Tool what i used for flashing is Flip from Microchip "FLIP 3.4.7.112 for Windows" with Serial programming on a breadboard.
i tryed to programm it with a TL866 Pro a brand new and a older Version but it wont programm it? i dont findout why.
maybe someone have a Agilent E3631A file for me?
my Display CPU wars also short (and hot),
the display is now dark and the PS beep one time if i switch it on, 5V on the Displayboard are ok.
Replaceing the Display driver IC not helped.
If a Button is pressed sometimes the unreg. will light thats all what it dose.
The unit Selftest (switchon with button pressed) do nothing
The Bias Supplies on my are ok.
the Display get IGFPSCK 8Bit clock packages one per second or so from the Main CPU and the display answer with some data on
FPDO. But no IGFPDI and no IGFPINT signals, U8 looks ok
Have you more ?
regards
kai