EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: Axtman on October 23, 2022, 07:09:03 pm
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The life of the meter that is....
I was a bit angry because I bought this old Fluke 77 on line. Sure enough the screen was horribly faded and unusable. Luckily I did not pay much money for the meter. I checked around the internet and no replacement LCD was available. So ithe meter was destined for the Great Electrical Equipment Test Lab in the Sky (aka the trash bin).
On a previous thread someone mentioned polarizing film. Dave made a video about replacing the rear film, but I found a video where a guy installed polarizing film on the front glass of the LCD. So I bought a sheet of film from Amazon and the results are below.
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The repair was so easy and cheap that I am going to do it to another Fluke meter that has a faded screen. BTW, the picture of the faded screen on the Fluke 77 above looks much worse in real life. Like I said before it was unusable before the repair.
If you are going to do the repair yourself be sure and cut the fim on the diagonal for highest contrast.
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If you are going to do the repair yourself be sure and cut the fim on the diagonal for highest contrast.
Be sure to try the full sheet and note optimal angle before cutting.
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I did. The optimal angle is 45 degrees.
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So it looks like the display aging is from the polarizing film and not the LC part.
So there can be a chance to revive fading LCDs.
The 45 degree angle is convenient. If wanted one can turn the ready cut filter inside out and get an inverted display.
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Worth of try, by the way I have found out, that in HP LA2405wg displays the foil is not glued (only adhesive force) - there are two, one matt another is glossy.
Since the polarization effect is done by stretching conductive material in one direction, maybe the killer is the temperature under which it can orient more randomly. If one has free foil, the test can be done without removing the old.
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8) Wow, you've made a quantum patch! 8)
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So it looks like the display aging is from the polarizing film and not the LC part.
So there can be a chance to revive fading LCDs.
The 45 degree angle is convenient. If wanted one can turn the ready cut filter inside out and get an inverted display.
I really shall try that on some old calcs. However I highly expect the LCD to be damaged (center appearing "clear" with black borders).
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Here is another Fluke 77/AN with a faded display saved from being thrown in the trash. I put the polarizing film right on top of the LCD glass and under the gray plastic cover.
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Realistically I would have not thrown those meters in the trash but instead put them on Ebay as "mint condition". :) But seriously, I would have listed them as a parts unit. But now with the revived display they can be used as is without being canabalized.