Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Troubleshooting Computer Displays
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 04-30-2020, 06:01 PM   #1
spleenharvester
Badcaps Veteran
 
spleenharvester's Avatar
 
Join Date: Mar 2010
City & State: UK
My Country: UK
I'm a: Hobbyist Tech
Posts: 710
Default Acer GR235H partially losing backlight

Unfortunately my trusty GR235H seems to be on its way out. After a while I lose two backlight segments at the bottom of the screen, always the same two. If I switch it off and on again it will work and keep working for hours.

A couple of times it's also been completely black screen with just the power light (I haven't shone a light on it yet to see if it's actually displaying anything), and again has started working properly after turning off and on.

What kind of problem am I dealing with here? If it's an LED strip how do I go about replacing it?
__________________
Dell E5500 | P8700 2.53GHz 3MB | GS45 GMA4500MHD | 4GB DDR2 | 64GB Crucial M4
spleenharvester is offline   Reply With Quote
Old 04-30-2020, 06:55 PM   #2
CapLeaker
Leaking Member
 
CapLeaker's Avatar
 
Join Date: Dec 2014
City & State: Atlantic Canada
My Country: Canada
Line Voltage: Ground, 0Hz
I'm a: Hobbyist Tech
Posts: 4,553
Default Re: Acer GR235H partially losing backlight

Those 2 LED’s are failing. The only 2 things you can do is to either turn the backlight level down, or replace those bad LED’s / LED strip.
CapLeaker is offline   Reply With Quote
Old 05-01-2020, 10:20 PM   #3
spleenharvester
Badcaps Veteran
 
spleenharvester's Avatar
 
Join Date: Mar 2010
City & State: UK
My Country: UK
I'm a: Hobbyist Tech
Posts: 710
Default Re: Acer GR235H partially losing backlight

Ah thought so. I'm guessing these are within the frame of the panel itself, and not on the back like in TVs - is this easily done or do you think it's worth just changing the entire panel out?
spleenharvester is offline   Reply With Quote
Old 05-02-2020, 05:09 AM   #4
spleenharvester
Badcaps Veteran
 
spleenharvester's Avatar
 
Join Date: Mar 2010
City & State: UK
My Country: UK
I'm a: Hobbyist Tech
Posts: 710
Default Re: Acer GR235H partially losing backlight

Also it just did the thing where the screen goes completely black again - just checked and there is an image, just no backlight at all - does this still suggest LEDs or is something else quitting too?
spleenharvester is offline   Reply With Quote
Old 05-02-2020, 05:47 AM   #5
CapLeaker
Leaking Member
 
CapLeaker's Avatar
 
Join Date: Dec 2014
City & State: Atlantic Canada
My Country: Canada
Line Voltage: Ground, 0Hz
I'm a: Hobbyist Tech
Posts: 4,553
Default Re: Acer GR235H partially losing backlight

the PSU part for the back light went into protection mode or one led went open in the string. LED's are current controlled, not voltage controlled. That's all right until one or more LED's fail, because LED's don't like to get more voltage that they are designed for.
CapLeaker is offline   Reply With Quote
Old 05-02-2020, 07:12 AM   #6
spleenharvester
Badcaps Veteran
 
spleenharvester's Avatar
 
Join Date: Mar 2010
City & State: UK
My Country: UK
I'm a: Hobbyist Tech
Posts: 710
Default Re: Acer GR235H partially losing backlight

So plot twist, I've ripped it apart and found a bloated pair of Su'scrud caps. Unfortunately my picture-taking capabilities are about as high-quality as these capacitors, but it looks to me like they feed into the 2x OZ9998GN backlight drivers. Do you reckon it's worth recapping these and seeing if it fixes the issue (I'm just wondering what the odds are of two LEDs going out at once!).

The board is an L0256-1M, and doesn't seem to have been documented elsewhere on this forum. C121 and C818, screenprinted back and front on the board (corresponds to bottom-right of rear photo).

EDIT - added a better photo of the circuit
Attached Images
File Type: jpg IMG_20200502_140452072.jpg (277.6 KB, 20 views)
File Type: jpg IMG_20200502_140633334.jpg (456.8 KB, 12 views)
File Type: jpg IMG_20200502_140620465.jpg (291.4 KB, 13 views)
File Type: jpg IMG_20200502_141610880[286].jpg (867.9 KB, 16 views)

Last edited by spleenharvester; 05-02-2020 at 07:17 AM..
spleenharvester is offline   Reply With Quote
Old 05-02-2020, 08:58 AM   #7
CapLeaker
Leaking Member
 
CapLeaker's Avatar
 
Join Date: Dec 2014
City & State: Atlantic Canada
My Country: Canada
Line Voltage: Ground, 0Hz
I'm a: Hobbyist Tech
Posts: 4,553
Default Re: Acer GR235H partially losing backlight

I wouldn’t go specifically buy capacitors, but if you had some good used ones to pop in on hand from a junker board, go ahead and try. It will not fix the 2 LED out situation.
CapLeaker is offline   Reply With Quote
Old 05-02-2020, 10:23 AM   #8
spleenharvester
Badcaps Veteran
 
spleenharvester's Avatar
 
Join Date: Mar 2010
City & State: UK
My Country: UK
I'm a: Hobbyist Tech
Posts: 710
Default Re: Acer GR235H partially losing backlight

Cool thanks, I'll give it a shot. I know it's a long shot but this panel has 4 current feedback channels with 2 LEDs on each, which as a layman makes me wonder if there's an issue with one specific channel. More than likely I imagine those two LEDs are kaput though.


Either that or the monitor will have to be scrapped, as I have zero confidence in my ability to access the LED strip
spleenharvester is offline   Reply With Quote
Old 05-02-2020, 10:30 AM   #9
CapLeaker
Leaking Member
 
CapLeaker's Avatar
 
Join Date: Dec 2014
City & State: Atlantic Canada
My Country: Canada
Line Voltage: Ground, 0Hz
I'm a: Hobbyist Tech
Posts: 4,553
Default Re: Acer GR235H partially losing backlight

You can tell which string is bad by measuring the voltage on each.
It makes a good project to learn.
CapLeaker is offline   Reply With Quote
Old 06-01-2020, 10:51 AM   #10
spleenharvester
Badcaps Veteran
 
spleenharvester's Avatar
 
Join Date: Mar 2010
City & State: UK
My Country: UK
I'm a: Hobbyist Tech
Posts: 710
Default Re: Acer GR235H partially losing backlight

Replaced the caps with some equivalent Panasonics, monitor has been running fine for 24 hours continuously on 100% brightness. Hopefully it lasts.
spleenharvester is offline   Reply With Quote
Old 06-13-2020, 12:04 PM   #11
spleenharvester
Badcaps Veteran
 
spleenharvester's Avatar
 
Join Date: Mar 2010
City & State: UK
My Country: UK
I'm a: Hobbyist Tech
Posts: 710
Default Re: Acer GR235H partially losing backlight

Just as a follow up for anyone who finds this in the future - monitor is still fine after two weeks of 24/7 at max brightness
spleenharvester is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2020
Powered by vBulletin ®
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 01:56 PM.
Did you find this forum helpful?