HP50g - High power consumption



#2

Recently, I ordered an HP50g and was astounded that the LOW BAT signal turned on after one night at the desktop (turned off). First, I blamed the enclosed batteries which might have been low and installed a fresh set. However, after one night the same finding. Some surfing in the web revealed that this is not an uncommon problem of this calculator.



Some measurements of power consumption showed the following picture according to the calc's status at ~6 V (where ~ stands for "approximately" not for AC :-):

Program running: ~100 mA

Key pressed: ~68 mA

Idle: ~50 mA

Off: ~40 mA



After some back and forth with HP services I got a replacement calculator today, and the first I did was the set of measurements on that machine:



Program running: ~65 mA

Key pressed: ~28 mA

Idle: ~12 mA

Off: ~26 µA



The less power consumption of about 3 orders of magnitude in the replacement would warrant a longer battery life of 3 years or so if the calculator was not used.



HP services said that I should care of the disposal of the first machine I received. However, it appears inadequate to me to throw an otherwise fully functional calculator away. At least, it can be operated with the USB cable from which it gets its power.

Or is there some means to repair this calculator? I read speculations about a burned Zener and the like. Is there a way to exchange malfunctioning components?


#3

Quote:
The less power consumption of about 3 orders of magnitude ...

Looks more like a constant ~40mA dissapearing somewhere.
Quote:
Or is there some means to repair this calculator?

Opening is easy enough. Remove the screen, see here. There are two screws on the top of the screen. Once these are removed, you can carefully pry the calculator apart. I used plastic levers from what is commonly known as "mobile phone tools" (see this example). The rest depends on how confident & equipped you are to trace the fault.

-B

#4

Quote:
The rest depends on how confident & equipped you are to trace the fault.

OK, I managed to open the calculator but I fear that my electronic skills are not that far developed at all.

Thanks anyway!


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