Acer LCD monitor not very bright and has yellow tint ? - Page 1
Forum section: electronics / repair

author: lordvader88
author_rank: Frequent Contributor
timestamp: May 11, 2018, 05:53:48 pm
content: I rescued an Acer P206HV and it works but the screen seems pretty dull/low brightness. The brightness/contrast controls work, and it's not too bad with it set to 100%/85%, but I bet it's not like that new.And overall it's pretty yellow tinted, I bet it wasn't like it new, I haven't touched the colors/etc yet.What hardware problems might cause this ? I'd have a go repairing it for fun/experience

author: Rasz
author_rank: Super Contributor
timestamp: May 11, 2018, 06:49:48 pm
content: CCFLs have a failure mode where they go yellow or even blue/pink when old, but this is LED monitor

author: Jwillis
author_rank: Super Contributor
timestamp: May 11, 2018, 09:04:36 pm
content: Cool / Pure White: Blue/UV diode with yellow phosphor.The LEDs are getting old because the UV Diode starts to yellow the resin encapsulation changing the spectrum.This is generally caused by heat.You should be able to change them out with new ones .

author: james_s
author_rank: Super Contributor
timestamp: May 11, 2018, 09:49:13 pm
content: I've torn down a couple LCD panels with this failure mode. What actually happens is that in addition to the CCFL lamps wearing, the plastic light spreader and diffuser layers turn yellow-brown. They then absorb more light and heat up, accelerating the process. One display I took apart these had become so brittle that the sheets crumbled into bits. Not much you can do really, although if you extract the panel intact you could try making a new backlight just for fun, or build an LCD window.

author: lordvader88
author_rank: Frequent Contributor
timestamp: May 11, 2018, 11:49:03 pm
content: Quote from: james_s on May 11, 2018, 09:49:13 pmActually I think I have 2 of them, both left outside for someone like me to claim. I never tried the 2nd 1, but the above 1 is my new backup.Didn't realize it was LED, I gleamed that sometimes the CCFL voltage could be low causing lower brightness, now I'm disappointed.The white in a text box is almost white, the blue tinted stuff on this page was yellowed. (I have my regular 27" 1440p LED working again, sleepmode problem)I suppose LED/s changing intensity over the years would upset the color balance, or something else that 'weather's' over the years, so maybe it's just to change the color balance for a very boring 'fix'I'll take 1 of them apart just to look around, never torn-down an LED LCD before.

author: Jwillis
author_rank: Super Contributor
timestamp: May 12, 2018, 01:46:00 am
content: CCFL or florescent lamps just usually fade and even sometimes begin to flicker over time eventually going dark .The spectrum appears to change but its just that they're not putting out the light.Usually the LEDs will be SMD on a flexible pcb strip around the edge of the thick plexi glass sheet sometimes they're attached to the main LCD panel and folded over the edges .Some older models used a series of LED bulbs .The white sheet is used to diffuse the light evenly and the rough greyish sheet diffuses glare .Even smd LEDs will "yellow" over time .Of course this shouldn't be mistaken for the yellow phosphor on the chip it's self.