fighting with a HP41c

[aurelio]

the match is always lost

happy new year to everybody....

I plugged into a not working tall key a block, restored with the Diego's kit, but the calculator still does not show signs of life.
Cosmetically very nice, the calculator does not seems apparently to have defects, I tested by changing the parts, the CPU, the "golden" connector, and they work, the problem seems to be located in the part which contains the display and the keyboard.
Apparently nothing to be remarked ..no corrosions, I mean, on the PC board interruptions or not soldered points, nothing that I can see.

I'm scared to disassembly the keyboard and the display to investigate the "dark side of the moon", for the reasons I wrote in older posts: I don't want damage the display with the soldering iron.

Is there a method to check the display without disassemblying it, and to check the healt of the two toogle switches?