Strange LCD repair outcome
in [Repair]
|
Prev: ~~~~~~~~~~~~~~ ARTHRITIS FOUNDATION ~~~~~~~~~~~~~~
Next: schematic diagram Harrison "K-4000" (K4000) MK-II 2x1000W wanted
From: pedro on 12 Jan 2010 08:49 On Sun, 27 Dec 2009 09:57:11 +0800, pedro <me(a)home.net> wrote: >I normally repair LCD monitors which are heading for landfill, and >they are turned over to needy/worthy groups (usually replacing olde >CRTs). Almost always, repairs are either "recap SMPS" or "replace >inverter transistors", and the hardest part is getting the case apart. > >Recently one Samsung 943NWX - presented as "dead" - had an odd >outcome. Replaced the bulging electros in the PSU and the unit came >to life, but with a dominant pink tinge to the entire screen area. >Normally I would ascribe this to backlight end-of-life, but three >things contradict this diagnosis. Firstly, hitting the menu button >with no video drive gives a small display "Test OK" (or similar) text >on a background which is white, so backlight colouration is unlikely. >Ditto if the menu system is fired up when a video signal is present - >pink screen but the menu b/g is pure white. Clearly the VGA input is >being incorrectly processed. Finally, the donor has confirmed that it >was white before failure. > >Has anyone experienced the video processor taking a hit when the SMPS >goes west with faulty caps? Clearly the unit doesn't warrant pursuing >a video chip replacement, and thereare no signs of distress on the >video board. Followup: Thanks to all for the comments. While there is a certain amount of adjustment available, it isn't enough to remove the pink tinge completely. Given that whites show as white from the test/menu, I stick with my view that VGA signal processing is shot. Whether the video board took a hit from the SMPS failure I won't know until another Samsung 740/940 crosses the bench, when I'll swap the boards.
From: stratus46 on 12 Jan 2010 23:45 On Dec 26 2009, 5:57 pm, pedro <m...(a)home.net> wrote: > I normally repair LCD monitors which are heading for landfill, and > they are turned over to needy/worthy groups (usually replacing olde > CRTs). Almost always, repairs are either "recap SMPS" or "replace > inverter transistors", and the hardest part is getting the case apart. > > Recently one Samsung 943NWX - presented as "dead" - had an odd > outcome. Replaced the bulging electros in the PSU and the unit came > to life, but with a dominant pink tinge to the entire screen area. > Normally I would ascribe this to backlight end-of-life, but three > things contradict this diagnosis. Firstly, hitting the menu button > with no video drive gives a small display "Test OK" (or similar) text > on a background which is white, so backlight colouration is unlikely. > Ditto if the menu system is fired up when a video signal is present - > pink screen but the menu b/g is pure white. Clearly the VGA input is > being incorrectly processed. Finally, the donor has confirmed that it > was white before failure. > > Has anyone experienced the video processor taking a hit when the SMPS > goes west with faulty caps? Clearly the unit doesn't warrant pursuing > a video chip replacement, and thereare no signs of distress on the > video board. It's set to component and getting RGB or vice versa. G²
From: pedro on 13 Jan 2010 09:43 On Tue, 12 Jan 2010 20:45:45 -0800 (PST), stratus46(a)yahoo.com wrote: >On Dec 26 2009, 5:57�pm, pedro <m...(a)home.net> wrote: >> I normally repair LCD monitors which are heading for landfill, and >> they are turned over to needy/worthy groups (usually replacing olde >> CRTs). �Almost always, repairs are either "recap SMPS" or "replace >> inverter transistors", and the hardest part is getting the case apart. >> >> Recently one Samsung 943NWX - presented as "dead" - had an odd >> outcome. �Replaced the bulging electros in the PSU and the unit came >> to life, but with a dominant pink tinge to the entire screen area. >> Normally I would ascribe this to backlight end-of-life, but three >> things contradict this diagnosis. �Firstly, hitting the menu button >> with no video drive gives a small display "Test OK" (or similar) text >> on a background which is white, so backlight colouration is unlikely. >> Ditto if the menu system is fired up when a video signal is present - >> pink screen but the menu b/g is pure white. �Clearly the VGA input is >> being incorrectly processed. �Finally, the donor has confirmed that it >> was white before failure. >> >> Has anyone experienced the video processor taking a hit when the SMPS >> goes west with faulty caps? �Clearly the unit doesn't warrant pursuing >> a video chip replacement, and thereare no signs of distress on the >> video board. > >It's set to component and getting RGB or vice versa. If I understand you proposition correctly, then no - it only has VGA input capability.
From: Jeroni Paul on 14 Jan 2010 17:46 Try to fiddle a bit the VGA connector and try another cable / source. Most of the times one of the color signals does not contact fully, sometimes due to the connectors getting old or some bad solder joint. On 12 Gen, 14:49, pedro <m...(a)home.net> wrote: > Followup: Thanks to all for the comments. While there is a certain > amount of adjustment available, it isn't enough to remove the pink > tinge completely. Given that whites show as white from the test/menu, > I stick with my view that VGA signal processing is shot. Whether the > video board took a hit from the SMPS failure I won't know until > another Samsung 740/940 crosses the bench, when I'll swap the boards.- Amaga el text entre cometes -
From: pedro on 14 Jan 2010 18:35
On Thu, 14 Jan 2010 14:46:29 -0800 (PST), Jeroni Paul <JERONI.PAUL(a)terra.es> wrote: >Try to fiddle a bit the VGA connector and try another cable / source. >Most of the times one of the color signals does not contact fully, >sometimes due to the connectors getting old or some bad solder joint. > >On 12 Gen, 14:49, pedro <m...(a)home.net> wrote: >> Followup: �Thanks to all for the comments. �While there is a certain >> amount of adjustment available, it isn't enough to remove the pink >> tinge completely. �Given that whites show as white from the test/menu, >> I stick with my view that VGA signal processing is shot. �Whether the >> video board took a hit from the SMPS failure I won't know until >> another Samsung 740/940 crosses the bench, when I'll swap the boards.- Amaga el text entre cometes - That was all checked out as soon as the pink tinge became evident. Also checked compponents on the video board for any signs of distress or dry joints, and finger probing as well. |