Re: 15C Keyboard Test Error Message #5 Posted by Vieira, Luiz C. (Brazil) on 26 July 2003, 11:10 p.m., in response to message #4 by professorkscc
Hi, professor;
in digital circuits, voltage levels below a minimum recommendation may cause the most strange and weird behavior, believe me. We're talking about MOS-based digital circuits, and in this case we may have larger voltage ranges, but if you consider that pressing a key in these calculators increases current consumption in about 300%, then having a previous low battery condition may lead to malfunction when a key is pressed, even if it is not when keyboard test is performed.
I observed once that ealier HP15C's with batteries "nearly-to-low-bat-condition" will sign this low-bat condition (flashing *) when performing keyboard test even when no keys are pressed, but will behave oppositely when in normal operation. I think these tests ([ON]&[+], [ON]&[×] and [ON]&[÷]) are like running programs and consume more power than regular use. If this is true, low batteries may cause [Error 9] in a normal unit running keyboard test.
My 2¢.
Luiz (Brazil)
Edited: 26 July 2003, 11:12 p.m.
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