T240 Monitor Backlighting Issue

[PsiQ]

Re: T240 Monitor Backlighting Issue

yup. took it off again. i managed to crack the upper right corner of the TN-Panels glass . Cracked: broad 3mm x 15mm length.

Guess i should be glad thats its only a quarter circle of 3cm in the upper right corner.

Now im gonna test the soldering point some time.
The Dead spot doesnt really matter for a secondary Desk-Screen or TV. Luckily the screen hast 1200 height pixels, not only 1080 height (= 1920x1200) so i can still watch full hd, when pulling it down a bit ;-).

And i have a usable screen until the new one arrives.


Nevertheless:
Thank you very much for the infos, also the infos coming from the other Forum pages, i learned a lot about the Flatscreens and the Problems appearing...

[PsiQ]

Re: T240 Monitor Backlighting Issue

okay... found it...
used a butter knife to push out the metal knobs holding diffusor panel screen etc together,
and then when getting out the HV cables out of the holder, one already came off.

Soo. Should i try to reattach the cable by soldering it again, or do i need to replace the tube ? -does the cable come off because of the defective tube, or is the tube defective couse the cable came off??

...=> Done already!
Ok, done and found it!

When i was looking for how to get to the lights, already one of the cables came off.
So i took off the metal+plastik clips, and took out the upper two lights.

They look kinda ok, but one had a bad connection/black and oxidized.
so i cleaned the cable, cleaned the bulb, made two new shiny soldering points, soldered it together AND added an shrinkable isolating tube (?) over the formerly loosened soldering point..

Clicked all and everything together again.. aaaand.
its working. At least the light for now.

Need to recheck it, but i think somehow i damaged part of the panel in the upper right corner when closing it. Dammit. Well, still better than a 19".

=> Error was: Soldering point/connection from wire to ccfl tube. oxidized and lost contact, leading to flickering of tube , and electric discharges which distorted the whole screen/control signals.



..I only wish i knew how i cracked the screen! Dammit! I always expected the lights to break, but not the panel!

Ok, the screen is going to the trash can when the new one arrives...
The corner is cracked, not that bad, but i have one vertical and one horizontal line coming from it into the screen.
AAAND. the light is flickering in 1flicker a second, coming from the fixed tube. Gonna try reducing the brightness, see if it helps.

So no use in keeping it as a secondary screen.
Too bad, would have really liked it. So its going to be a new 24" 1920x1200, and a new 19" 1280x1024next to it.

... ok, reducing the brighness only leads to an damn humming noise. i know, thats been there from the beginning, the pwm+inverter are crap when dimming.. but brightness at 100, contrast 95 is ok, no flickerin. bit of tearing in the upper right screen.

thx.

[PsiQ]

Re: T240 Monitor Backlighting Issue

Okay, so i think im trying to make a visual check of the lamps.

Thank you for the reply. I've read both links.

Perhaps im lucky enough to have a bad lamp one currently blowing up,
and i can see it directly.

If anybody still needs pictures from PCB or part numbers, i can provide them since the monitor is still disassembled.

#1: get out lights
#2: check lamps
#3: get replacement... (in germany)

..Dont like the high voltage coming from the inverter..


--So i could basically use the electronics from a working (small) light bulb to test the ccfl-tubes ?


.. I think i am going to buy a new samsung 1920x1200 screen,
but it would be really great if i could reanimate the old screen. The Standalone TV-Function is kinda cool for watching tv in the background while playing. Less Power Consumption compared to my 42" Plasma.

[budm]

Re: T240 Monitor Backlighting Issue

Sounds like you will need test lamp to find out what is going on or you will have to take the screen apart to inspect the lamp assemblies.
https://www.badcaps.net/forum/showthread.php?t=19987

Bad lamps:
http://s807.photobucket.com/albums/y...klight%20lamp/

[PsiQ]

Re: T240 Monitor Backlighting Issue

Hello everyone!
I found this Thread over Youtube and Google, and im also having problems with my samsung t240HD.



I shut it down and took it apart BEFORE it totally quit to function,
so i can tell, that the signal-board etc seems to be working just fine.

The Problem i had, was a slight flickering in the upper part of the screen.
When running for some time (1h), perhaps due to getting warm, the screen/picture flickered combined with a high frequency humming noise,
leading to distortion over the screen.

I'm guessing either the inverter or one of the ccfl lamps are close to dying.

As for the inverter, i measured the output pins mentioned earlier in this thread, which are both having 1,0xx.. k-Ohm resistance. (903 Ohms mentioned there)
So the inverter seems fine.
--What resistace should be on the input side of the inverter??

Due to the light flickering a bit, i guess there might be a lamp going bad.

I think the tube/lamp isnt functioning properly (flickering), leading to overpowering the inverter, which then leads to interference which influence the LCD-Picture-Data.


Any hints or suggestions?

I wanted to try to disable the Inverter/Backgrund light, to see if its only from the Backlight.

I found the "PWM brightness" Pin on the cable. To disable the lighting, do i have to set it high (3V .. 5V?) or low = 0V.
--With doing so, i could eliminate the possibility of a bad Signal Mainboard.


--As said earlier, the screen is still working, but i didnt want to wait until the existing problem and flickering kills another Component, not harmed yet.


Capacitors and PCB look all fine, no marks or bad caps visible.
Switching on and off and signal/picture are working just fine.

I dont think i would have any problems of changing the inverter, except the time for the delivery, but i also dont think its broken (yet)..

[retiredcaps]

Re: T240 Monitor Backlighting Issue

If you mean IC101 then i have to disappoint you by telling the part number is not readable.

Sorry, I meant IC101.

If you have no ESR meter, concentrate on bad ccfl wiring (especially the return wiring).

[Snev]

Re: T240 Monitor Backlighting Issue

Thanks for the information. Seems i'm quite lost without an ESR meter

U101 doesn't seem to be on the back side of the board. If you mean IC101 then i have to disappoint you by telling the part number is not readable.

[retiredcaps]

Re: T240 Monitor Backlighting Issue

The transformer resistances are: 905 and 921, so well within the 3% tolerance.

1) What is part number U101 (on the backside of the power board)? This has nothing to do with 2 seconds to black, but I need that information to help someone else.

2) 2 seconds to black can be (most likely)

a) bad caps
b) bad ccfls
c) bad ccfl wiring (especially the return wiring)
d) bad secondary windings on the inverter transformer

More details starting with post #19 at

https://www.badcaps.net/forum/showthread.php?t=10419

Also, see budm's Inverter tester using old CFL

https://www.badcaps.net/forum/showthread.php?t=19987

3) Your transformer readings suggest they are likely good.

4) You cannot test whether a capacitor is good or bad with a multimeter. You need an ESR meter.

5) Post clear focused top down pictures of all your boards following my sig file below exactly. We want the picture compositions like so

https://www.badcaps.net/forum/showpo...94&postcount=1

[Snev]

Re: T240 Monitor Backlighting Issue

My apologies for posting on this rather old thread.
I have the same problem as stated (multiple times) above. I've checked all capacitors. They all seem to block DC and the voltage of the electrolytic caps rises when I put the diode-tester over them. I only have a simple multimeter so I can't check other parameters. There's also no visual indication of damaged components on the board. I've also checked all the diodes.

The transformer resistances are: 905 and 921, so well within the 3% tolerance.

Does anyone have an idea?

edit: I also checked a number resistors (when possible) and of course the fuse. I've also read the 'A guide on how to troubleshoot 2 seconds to black' thread which teaches me that I probably can not do anything more with my multimeter. Still, if anyone has another idea (besides guessing and replacing all the components), it would be much appreciated.

[PlainBill]

Re: T240 Monitor Backlighting Issue

Measured the resistance between the points like above:

Red: .930
Yellow: .605

Bad transformer. Plenty of information on getting a replacement in this thread.

PlainBill

[coreyc123]

Re: T240 Monitor Backlighting Issue

Measured the resistance between the points like above:

Red: .930
Yellow: .605

[mucoast]

Re: T240 Monitor Backlighting Issue

http://youtu.be/_UEGD-uhkTo

Probably not needed anymore, but goes over a few more details of taking the monitor apart.

[jsog]

Re: T240 Monitor Backlighting Issue

Scorching like that isn't good, but it doesn't mean the transformer is bad. Check the output windings with an ohmeter. I'd also replace all the caps except the largest. It's possible that failing caps are causing the transformers to fail. Or the transformers are just badly made.

[coreyc123]

Re: T240 Monitor Backlighting Issue

Got mine all the way apart. I was hoping it was just the capacitors but it looks like it is something like the guy who started this thread.

Brown marks on the board.

[mucoast]

Re: T240 Monitor Backlighting Issue

When I took mine apart yesterday, I took some video. I talk about how I got the panel apart, as well as how to remove the components to get to the power supply. If youll be patient, I will put it up on Youtube later this afternoon.

THe long and the short of it is this: After taking out the stand and the two screws on the bottom-center of the back of the panel, put a screwdriver in either slot on the back of the panel (use a large one to get a lot of leverage). Pry the back panel up until it pops on either side. Then, work your way from the non-menu side all the way around to the side with the pushbutton menu. This worked fine for me, though I am pretty sure its impossible to do without a few scuffs on the glossy-black finish...

[Rtech]

Re: T240 Monitor Backlighting Issue

On most monitors you can ease up the top or bottom of the Surround from the Screen,and that can then let you put in a flat object to open the rest up.

[mariushm]

Re: T240 Monitor Backlighting Issue

Yeah, I have one of these T240 on my desk - really sweet monitor, hard to get one these days with 1920x1200 resolution.

The leg is hard to mount and hard to pull out, makes you worry you'll break it, and the way the case is made just sucks as you almost can't open it without damaging the case.

[coreyc123]

Re: T240 Monitor Backlighting Issue

There were 2 screws on the front of it that I had already removed them. However it turns out I was just to worried about breaking it. The base piece just slide out (with a little prying). and found the other 2 screws.

Now I dont feel so dumb, just kinda

[jsog]

Re: T240 Monitor Backlighting Issue

There are probably two screws in those holes in the stand. Take those out, take the back of the stand off, and then there are probably at least two more holding the bottom of the monitor together. Don't use a screwdriver to pry, they scar the plastic. There are plastic tools for that, and credit cards and guitar picks sometimes work.

[coreyc123]

Re: T240 Monitor Backlighting Issue

Don't mean to kinda jack this thread but I am having the same issue. I have a t240 that turns on for one second and then off goes the backlight.

I have been trying to figure out how to take the stupid thing apart for a while now. I now I feel like the stupid one.

I figure you put like a small flat blade into the slits on the sides on the back but I can't get the center part of the stand holder to come off.

Pictures attached of my monitor. Any help would be great.