Re: LED failure Message #2 Posted by Vieira, Luiz C. (Brazil) on 29 July 2003, 4:27 p.m., in response to message #1 by Matthias
Hi, Matthias;
If I am not wrong, all classics have a complete position in the display dedicated to the minus sign for the exponent of ten. From the Woodstocks on, you'll see less digits and a "shared" portion (two or three digits) that act sometimes as least significant digits for the mantissa and others as the exponent of ten.
I'm mentioning these facts because if it is possible to activate all segments in this position then we could verify if it is a matter of bad contact or not. Anyway, based on what you described, all of it may be out of operation. This is not bad, because each digit has a dedicated connection common to all cathodes (in some cases may be anodes) and each anode in all segments taht share the same position (a, b, c, d, etc.) are connected together. This is a common arrangement and is driven by multiplexed signals. You probably know about that, but maybe others don't.
Well, it is possible that a single bad connection is the cause. IN all Classics (HP55, HP65, etc.) and in the HP67, the display is arranged in four blocks with four digits each. I would do the following: I'd open the calculator and identify the block that contains the exponent signal (the rightmost) and I'd carafully and re-solder all of its terminals. If you decide you should test before or inspect to find with pin is not connecting, no problem. To be honest, I'd do the same if I have the time to search for the problem.
Hope this helps.
Success! (I did not spell check the text, so forgive my mistakes, please...)
Luiz (Brazil)
Edited: 29 July 2003, 11:50 p.m. after one or more responses were posted
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