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Bad HP41 display? Shows @'s and whistles
03-10-2017, 07:51 AM (This post was last modified: 03-10-2017 11:33 AM by isanchez.)
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RE: Bad HP41 display? Shows @'s and whistles
Hi,

from my experience repairing many HP41 series calculators:

-It is not a CPU board problem (I have repaired more than 30 HP41's and never found a failing board).

- It looks very much a problem in the zebra contacts: for any reason it is not doing a proper contact. You must assure a good contact. Check that the bottom screws are tight (not excessively or you will break the plastic holes! Check that they are not already broken, this makes the screws not to work properly) . Is the zebra connector the "golden" type? or is it the rubber one? From my experience, the "rubber" type does cause problems when "reused". It seems it gets a permanent deformation that makes difficult to get a proper contact. An extra "pressure" is needed to get the contact, but this is risky. It is not the case for he golden versiĆ³n.

- Could also be the upper flex connection. If it is original (not the reconstructed flex) it shouldn't be. Check that the upper screws do work fine.

- IN ALL CASES: Do not press too much the screws, or you will ruin the back plastic cover!

- About the DISPLAY: you can easily check the continuity of the contacts with a multimeter and visually by pulling up with a screwdriver each of the contacts. If there is a defect in the soldering you will find it very easily. If all is OK, then we can think in the display driver (not the LCD part).


I am pretty sure it is something in the zebra. You have to insist in finding the proper connection (try to find a golden zebra if you have the rubber version)...after some tries, then works, from my own experience.

EDITED: if it whistles, definitively this does not sound like a problem with the display.

Good luck!
Regards

Ignacio
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RE: Bad HP41 display? Shows @'s and whistles - isanchez - 03-10-2017 07:51 AM



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