HP Forum Archive 06

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HP-41CX clock quirk Message #1 Posted by David Smith on 5 July 2001, 6:08 p.m. I have an HP-41CX with a little strange little quirk in its clock. Whenever the batteries are changed the clock disappears from the system for a few minutes. SHIFT-ON just turns the system off. After about 1-5 minutes after the batteries have been inserted the clock starts working normally. Note that if the batteries are re-inserted fairly quickly (say less than 30 seconds) the clock stays put, but it disappears long before a "MEMORY LOST" condition occurs. Has anyone seen this behavior before or know of a cure?

Re: HP-41CX clock quirk Message #2 Posted by David Smith on 7 Aug 2001, 5:15 p.m., in response to message #1 by David Smith If any body else has this problem the cause was the 22 megohm resistor next to the crystal. It an open circuit. I originally did not want to measure its value in circuit because my ohmmeter puts a fairly high voltage across its leads on the high-ohms range. When I finally unsoldered the resistor, it came apart into three pieces.

Re: HP-41CX clock quirk Message #3 Posted by Ion Abraham (New Mexico) on 8 Aug 2001, 1:27 p.m., in response to message #1 by David Smith David, I am fairly sure that this is not a "quirk," meaning "it's not a bug, it's a feature." When the BAT indicator comes on, meaning that the batteries are low, you no longer have access to the clock. It's still running, but the clock uses a lot of continuous power, so they made it inaccessible under a low battery condition. Note also that if you display the clock, the calculator will no longer automatically turn off after a while, so that is a sure way to run down your battery. Regards, Ion Abraham Albuquerque, New Mexico

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