The Museum of HP Calculators

HP Forum Archive 14

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Message #1 Posted by Ken on 11 Dec 2003, 9:54 a.m.

My HP-41CX shuts off shortly after turning it on. When I execute the "ON" function, it will stay on until I shut it off. Apparently the automatic "shut-off" timing circuit is corrupt? Can anyone address the possible problems? Do I need to take it to a Service Center? Can anyone refer me to a Center in NJ?

Message #2 Posted by Ed on 11 Dec 2003, 10:21 p.m.,
in response to message #1 by Ken

The HP-41 actually has three power modes: On, Sleep, and Off. It actually spends most of its time in Sleep mode - it is only On for a few seconds after you press a button. In Sleep mode, the 41 keeps the display active but shuts down the CPU circuit. The mode control is actually managed by the LCD display circuit.

The bottom line is that this problem is typically related to connection problems between the LCD circuit board and the main circuit board. There are several metal jumpers that connect the boards ... the solder joints can fatigue and fail. If you view them under magnification and probe with a sharp tip, you may see a crack.

The repair is a simple matter of resoldering (with a fine tip) the connection(s).

Good luck.

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