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HP Forum Archive 13

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HP41C: High current consumption
Message #1 Posted by Vieira, Luiz C. (Brazil) on 3 June 2003, 12:23 p.m.

Hi, folks.

I have an HP41C in hands (top keys, not mine) with a dimmed display. I tested another mainboard on it and the display is happily clear and crispy. I brought the original maninboard back and measured current consumption in this unit and in another one with a better behavior. These are the figures:

Operation    41C High-curr  Normal 41C
calc OFF         40 ľA          40 ľA
calc ON        6.88 mA         760 ľA
key pressed   11.20 mA        6.38 mA

I just want to know where to start looking for "bogus". As the display is dimm, I firstly thought about the LCD driver, but with these figures, maybe someone has a better starting point.

Thanks for any guidance.

Luiz C. Vieira - Brazil

      
Re: HP41C: High current consumption
Message #2 Posted by WAG on 6 June 2003, 3:45 p.m.,
in response to message #1 by Vieira, Luiz C. (Brazil)

Very wild guess.... leaky electrolytic capacitor?

            
Re: HP41C: High current consumption
Message #3 Posted by Vieira, Luiz C. (Brazil) on 6 June 2003, 9:47 p.m.,
in response to message #2 by WAG

Hi, WAG;

thank you! Not so wild, could be. I thought about this:

1 - NUT processor is running low-power O.K., RAM/ROM too; at least, 40ľA tells me so.
2 - LCD module works fine with other mainboard (I measured the O.K. values with this module).
3 - I'd guess the LCD drive RAY-xxxx (or something like this) is messing up because it's one of the only "guys" that's not running when the calculator "hybernates" in low-power condition.

I want to listen the sort of clever guesses like yours. If there is any capacitor that's short-circuited then I must search for it. Oh, yes; the board is completely clean, it's a beauty! No corrosion or leakage signs! It's an orginal HP41C's board with RAM 1LA701 to 1LA705, in perfect condition, and I think it's owner wants to keep it this way. I have newer boards to replace, but I'll try to fix it.

Thanks a lot!

Luiz C. Vieira - Brazil

Edited: 8 June 2003, 9:59 p.m.

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