HP-71B LCD Problem! How Common?

[Stefan_Titan2944A]

Hi,

a Zebra issue is unlikely.

The HP71B has two PCBs:
- IO PCB ( can be removed ) containing
Power Supply, RAM and IO ports
- Keyboard PCB ( hardly removable) containing
CPU, Keyboard, Card Reader, Display RAM and LCD driver chips

Both boards are connected via Zebra (old versions) or flex cable.
This connection is the System Bus - it will certainly not corrupt the display
due to missing connections.

The LCD itself is soldered on the Keyboard PCB.

The problem is most likely the LCD itself - connection of electrodes to
top and bottom glass substrates. Both glass layers are seperated by a
spacer layer, which shrinks. This may cause missing or additional lines.
Hence, when moderate external force is applied, missing lines usually
re-appear.

Use at own risk:
One of my HP71B had the same issue and was successfully
revived by moderately heating the LCD (hair drier). Try the areas
of issue first. Extend to the whole LCD if necessary.

- Stefan