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

 
Thread Tools Display Modes
Old 05-19-2017, 02:34 PM   #1
fritzycat
New Member
 
Join Date: May 2017
City & State: Los Angeles, CA
My Country: USA
I'm a: Knowledge Seeker
Posts: 5
Default HP w2408 LCD - Buzzing Noise when Brightness < 100%

I have an HP w2408 LCD that makes a constant buzzing noise when the brightness is less than 100%. If I turn the brightness all the way up to 100%, the buzzing stops. It has been making this noise for years, I've just now decided to try to do something about it! Except for the buzzing, the monitor works great.

I'm not sure if the issue is with something on the inverter board or the CCFL tubes themselves. I've been searching the forums, but haven't found another post that has a solution to this issue (yet).

I've disassembled the unit, but I can't seem to isolate the buzzing to a single component. The buzzing starts immediately when the CCFLs light up after I power on the device. I've tried poking at each of the inverters with a plastic stick to see if the noise might change when some pressure was applied - it didn't. None of the inverters are showing any signs that they have been overheating.

The capacitors appear ok - no bulging, burning or leaking of electrolyte.

I tried disconnecting one of the CCFL tubes. When I do this, and power the unit on, the remaining CCFLs light up for about a second (without any buzzing!), but then the monitor shuts down about 1 second after that. I'm assuming this is because of some fault protection circuitry. It doesn't seem to matter which of the 6 CCFLs I disconnect - I get the same result - no buzzing, but the monitor shuts down after 1 second.

I've attached a few photos for reference - the model number on the inverter board is QLI-002. A yellow sticker on the board has the numbers: 790111420000R S1100BA00NY33 0728

Any suggestions on the procedure to troubleshoot this? I'll keep searching the forum to see if I can find anything...

Thanks!

-Fritz
Attached Images
File Type: jpg 20170519_131420.jpg (631.2 KB, 18 views)
File Type: jpg 20170519_131522.jpg (563.3 KB, 16 views)
File Type: jpg 20170519_131314.jpg (857.1 KB, 19 views)

Last edited by fritzycat; 05-19-2017 at 02:46 PM..
fritzycat is offline   Reply With Quote
Old 05-19-2017, 03:09 PM   #2
fritzycat
New Member
 
Join Date: May 2017
City & State: Los Angeles, CA
My Country: USA
I'm a: Knowledge Seeker
Posts: 5
Default Re: HP w2408 LCD - Buzzing Noise when Brightness < 100%

... and moments after I posted my question I saw the excellent sticky post by 'retiredcaps': http://badcaps.net/forum/showthread.php?t=10419

I'll probably start by replacing the capacitors (470uf 35v) because that is easy and the caps are 10 years old.

If that doesn't do the trick, I'll try testing for dying CCFL tubes by disconnecting them one at a time and connecting another CCFL in its place. I'm just not sure if bad CCFLs buzz (or might cause the inverter to buzz) when they are going bad. Can anyone confirm this?
fritzycat is offline   Reply With Quote
Old 05-20-2017, 08:30 PM   #3
fritzycat
New Member
 
Join Date: May 2017
City & State: Los Angeles, CA
My Country: USA
I'm a: Knowledge Seeker
Posts: 5
Default Re: HP w2408 LCD - Buzzing Noise when Brightness < 100%

So, I've got some 470uf 35V capcitors. However, they are temperature rated 105C. The capacitors on the inverter board are rated 125C. Can anyone tell me if the different temperature rating is relevant in this application? Do I need to order some 125C caps?

Thanks!
fritzycat is offline   Reply With Quote
Old 05-21-2017, 03:52 AM   #4
Ian Paul
Member
 
Join Date: Mar 2017
City & State: Shropshire
My Country: United Kingdom
I'm a: Student Tech
Posts: 23
Default Re: HP w2408 LCD - Buzzing Noise when Brightness < 100%

Transformers can buzz, is it coming from inverter board?
Ian Paul is offline   Reply With Quote
Old 05-21-2017, 12:18 PM   #5
fritzycat
New Member
 
Join Date: May 2017
City & State: Los Angeles, CA
My Country: USA
I'm a: Knowledge Seeker
Posts: 5
Default Re: HP w2408 LCD - Buzzing Noise when Brightness < 100%

Thanks for the reply. The buzz does appear to be coming from the inverter board, but I can't seem to isolate the buzz to any one component. There are 12 transformers on the board so I thought I would start with replacing the caps to see if that helps. I haven't diagnosed an issue like this in the past, so I'm open to any and all recommendations.
fritzycat 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 - 2017
Powered by vBulletin ®
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 09:42 PM.

Did you find this forum helpful?