EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: ErwinsCat on November 04, 2020, 11:16:25 am
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I recently scored a 2channel fluke PM2812 system power supply, I wanted to mod and hack the unit to use it as benchtop power supply. I had some minor issues which fixed, there is a small issue and I might post a new topic for help.
this post is about fixing the LCD backlight. I tried to find a suitable ELbacklight for the unit but the only seller I found was in the UK and despite their wide range of sizes, the only option was to buy a long ribbon and cut it to the size and everybody considers is a bad idea because it damages the seal and causes the light die prematurely.
I saw someone used an iPhone backlight for another project online and thought to give it a go an after 1 hour fiddling with it I have to report it worked beautifully, even better than what I expected.
the only hiccup in the surgery happened when I tried to trim the backlight to correct size and cut the flex board and severed the backlight LED connection but fortunately there was enough conductive left on the last led to solder a tiny enamel wire on both sides of the LEDs (4 LEDs in series). for the powering LEDs, I wanted to use 7812 to bring the 24v to 12 as 4 LEDs in series worked perfectly on 12V and draining 10 ma. unfortunately couldn't find any 7812 in my stuff and didn't want to mess with switching converters either. anyways I figured the easiest way to power the LEDs was just a resistor in series and it powered the LEDs on 24V under 9 ma. I taped the existing 24V connector on the PSU board.
anyways the moral of the story is you can use this backlights for almost everything as they are dirt cheap, low voltage / low power, very low profile and come in different sizes. I'm assuming the tablets using similar technology and if that's true you can find a match for almost any LCD size. and if you prefer coloured backlight you can use filter to change the white light.
I didn't mean to create this post so I didn't take good photos before I cut the backlight but it is not hard to imaging cutting a flexible backlight. I'm planning to add a backlight to my Tektronix dmm916 multimeter and if I find a way to fix the voltage issue, I might take better photos and document the procedure.
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