Re: HP-34C display problems Message #2 Posted by Vieira, Luiz C. (Brazil) on 9 Jan 2003, 8:14 p.m., in response to message #1 by Don Davis
Hi;
I disassembled a few Spices with bad contact. All of them, no exceptions, where the sandwich, no-solder, pressure type. Simply cleaning and in one case using a metal polisher solved the problem.
The good news for me about your post is that the same segment in all digits appear loose. The process to "lit" them up is called "multiplex(ing)" and the same segment in all digits share one common connection each. This reduces the number of "wires"(connections) for the display segments (if you already know about this, just think it's for those who don't know, please...). This way, one single bad contact in one terminal of the display assy OR the control IC (CPU) is enough to cause the problem you describe.
If yours is a soldered-chips type (and I do not remember feeling differences from one type to the other... well, long time ago), no matter, too: resoldering terminals is not hard, too.
In both types, two major difficulties for those who have never done it before:
opening the calculators' case AND
disassembling the inside parts
If you already know how to do it, no matter. if you don't, it would be better to count on help from someone who have already done it. Just for making it easier.
Hope you have success.
Best regards.
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