The Museum of HP Calculators

HP Forum Archive 21

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Contrast in HP42s flush display , another one....
Message #1 Posted by aurelio on 1 Sept 2012, 8:47 a.m.

Hi all! I read in the archives several posts about the issue, but actually I've not understood if the earlier 42s's display contrast can be improved, by modifying the hardware or if the procedure described by Lyuka here, is to apply only when display is not readable at all (caused by broken switching transistor in the processor)! On my 42s version C the display is 4-5 times brighter than on the other 42s flush display version A. In the first I can read the display always, while in second one with difficult and only in full a light condition. If compared with the DavidShenk's issue (here)If you look at it straight you can read perfectly, in my calculator. When I try to adjust the contrast, the contrast changes and I see the dots' matrix of the blank bottom becoming darker, but the contrast between the displayed chars and the bottom is not all!

Now what I'm wondering is if this is the max performance of that version display or if it could be increased....what do you think about?

PS: if I look in front at the display (straight) I must increase the contrast (EXIT and +), viceversa otherwise (if I'm looking at the screen from a very low angle)

Edited: 1 Sept 2012, 10:29 a.m.

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