HP41cx problem

[Paul Franceschi]

I have display problems as follows: when I turn it on, only the upper half of the screen shows and for me to get it to show properly I have to hold one corner of the calculator down, specifically the left bottom corner, or it has to be on a hard surface with all four feet firmly planted. It will not show unless I am sqeezing it or holding down a corner. I can wiggle the calculator and the display comes and goes. If I pick it up the display disappears completely or just the upper half. I can wave it around in my hand and the display will come and go. If I squeeze it slightly the display will stay, you get the idea. Is there something loose? I have played with the batteries, cleaned the contacts, etc, but have not taken it apart.

Any suggestions?

[David Smith]

It sounds like you have a broken (or stripped out) bottom screw post. The fullnut HP41 machines have a CPU card that connects to the keyboard via a "zebra" type connector that uses the compression of the case to make contact. Typically the machine gets dropped and one or more of the screw posts breaks causing bad contacts. Another problem is the screw posts can split vertically.

You can try to glue the post back using a plastic welding solvent (typically dichloromethane) available in small bottles at most hobby shops. Despite what the bottle says let the joint dry for at least 24 hours.

[db (martinez, ca.)]

another possibility is that one or more of the little tabs that connect the screen with the pcb have come un-soldered. they may not be making connection and still look tight so look real close. if this turns out to be the problem the good news is that it is an easy fix; they are relativly big and out in the open.