HP Forum Archive 08

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HP 41-CX Odd Behavior - Advice? Message #1 Posted by emartin on 12 June 2002, 11:33 p.m. I have a 41-CX that I recently put back into service after my 32S-II Enter key went out on me. The calculator works fine, but turns itself off after about 14 seconds instead of the normal 10 minutes. I put in fresh batteries, took it apart & cleaned internal contacts, let the capacitors discharge for 5 days, and I still have a quick shut-off calculator. The "low batt" flag is not set, and if I execute the "On" function, it will stay on indefinitely, just like it's supposed to. I suppose I could run "On" every time I power up, but that is inconvenient to say the least. Any advice? P.S. I bought a replacement 32S-II a couple of months ago. Has anyone else noticed what junk the recent Pioneers out of Indonesia are? - Ed

Re: HP 41-CX Odd Behavior - Advice? Message #2 Posted by John K. (US) on 13 June 2002, 1:50 a.m., in response to message #1 by emartin The [41CX] works fine, but turns itself off after about 14 seconds instead of the normal 10 minutes. Out of curiosity, does your 41 have the clock speed-up modification? If so, that could be the problem. You can test for this by clearing the auto-shutoff flag (the number escapes me at the moment) and checking to see if the problem persists.

Re: HP 41-CX Odd Behavior - Advice? Message #3 Posted by emartin on 13 June 2002, 10:01 p.m., in response to message #2 by John K. (US) No, it's a standard-issue CX, no mods. When I clear the auto-shutoff flag, it stays on. Does anyone know if the CX uses a digital timer for the shutoff, or is it some kind of analog timer that may be subject to drift (e.g., leaky capacitor)?

Re: HP 41-CX Odd Behavior - Advice? Message #4 Posted by Andrés C. Rodríguez (Argentina) on 14 June 2002, 7:37 a.m., in response to message #3 by emartin In the 41 C/CV the "off" timer was located in the display (the only part which is working in the meantime between keystrokes or running programs) , but I don't know if in the CX, due to the TIME functions, there are other considerations.

Re: HP 41-CX Odd Behavior - Advice? Message #5 Posted by emartin on 14 June 2002, 10:02 p.m., in response to message #4 by Andrés C. Rodríguez (Argentina) Thanks. This makes sense, since I also occasionally get some ghosted segments (always segments that shouldn't be on, but are - partially). I wonder if I have a problem with the PCB, or worse, driver chip, on the dsiplay driver board. Or perhaps there is a "stay on" signal from the display driver to the main PCB that is broken. Also, the calculator never turns itself off if I am running the stopwatch, a program, or I have recently pressed a key. Does anyone know where I could get my hands on a schematic?????

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