help to solve back display in 2sec

[gautam mhz]

samaung symcmaster 920nw lcd monitor.when turn on it gone black in 2sec .what to do sir

[alexanna]

Re: help to solve back display in 2sec

I am a learning student on this site.One of the things I have learned is to describe the problem thoroughly as you can.Post the clearest photos as possible of the front and back of both boards,I have had good luck with windows live photo gallery it lets me resize the photos to keep under the 2000 by 2000 limit.
And then keep your fingers crossed that someone comes to your rescue

[nuhhht]

Re: help to solve back display in 2sec

Can you be specific on 'gone black'

When the monitor goes black does the power lights on the bezel stay lit? Do they turn amber? Turn completely black?

[ben3843100]

Re: help to solve back display in 2sec

I guess it's up to me to resurrect this threat. I have a Samsung 920nw in my possession with the same problem as the original poster; the display turns on fine and displays the input signal for about 1-2 seconds, then the display goes "black." The power LED stays on when the display blanks out. My first thought was to replace the capacitors on the combination power / inverter board. I ordered and just completed replacing all of the capacitors on this board.

The display problem has not changed. It still blanks out after about a second. I read in another post on Badcaps that something on the inverter board is not working correctly. I believe I read that the lamps operate in a loop, with the top two lamps (plugs) being driven by one part of the inverter board, and the second set of lamps (plugs) being driven by the other part. This would seem to make sense since it looks as if there are two sets of components on the inverter side of the board. Unplugging the top two lamp plugs and powering on the monitor causes the image to stay active for about 3-4 seconds. The same is true if I unplug only the bottom two plugs.

Any assistance or feedback would be appreciated. I have trolled these forums quite a bit over the last two weeks, so if this problem has been covered on another tread I apologize.

Thanks in advance!
-Ben

[jetadm123]

Re: help to solve back display in 2sec

I guess it's up to me to resurrect this threat. I have a Samsung 920nw in my possession with the same problem as the original poster; the display turns on fine and displays the input signal for about 1-2 seconds, then the display goes "black." The power LED stays on when the display blanks out. My first thought was to replace the capacitors on the combination power / inverter board. I ordered and just completed replacing all of the capacitors on this board.

The display problem has not changed. It still blanks out after about a second. I read in another post on Badcaps that something on the inverter board is not working correctly. I believe I read that the lamps operate in a loop, with the top two lamps (plugs) being driven by one part of the inverter board, and the second set of lamps (plugs) being driven by the other part. This would seem to make sense since it looks as if there are two sets of components on the inverter side of the board. Unplugging the top two lamp plugs and powering on the monitor causes the image to stay active for about 3-4 seconds. The same is true if I unplug only the bottom two plugs.

Any assistance or feedback would be appreciated. I have trolled these forums quite a bit over the last two weeks, so if this problem has been covered on another tread I apologize.

Thanks in advance!
-Ben

At this point, we will need good clear focused photos of the entire top and bottom of the power/inverter board. A photo of the logic board would also be good. Also, what brand/series of caps did you use as replacements?

[retiredcaps]

Re: help to solve back display in 2sec

the display turns on fine and displays the input signal for about 1-2 seconds, then the display goes "black."

1) See post #13 and #14 at

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

2) Post pictures after reading misc suggestion #1 on the guide above.

3) What brand and series did you use for replacement caps?

4) Section #4 and #5 may be other causes for 2 seconds to black.

[PlainBill]

Re: help to solve back display in 2sec

I guess it's up to me to resurrect this threat. I have a Samsung 920nw in my possession with the same problem as the original poster; the display turns on fine and displays the input signal for about 1-2 seconds, then the display goes "black." The power LED stays on when the display blanks out. My first thought was to replace the capacitors on the combination power / inverter board. I ordered and just completed replacing all of the capacitors on this board.

The display problem has not changed. It still blanks out after about a second. I read in another post on Badcaps that something on the inverter board is not working correctly. I believe I read that the lamps operate in a loop, with the top two lamps (plugs) being driven by one part of the inverter board, and the second set of lamps (plugs) being driven by the other part. This would seem to make sense since it looks as if there are two sets of components on the inverter side of the board. Unplugging the top two lamp plugs and powering on the monitor causes the image to stay active for about 3-4 seconds. The same is true if I unplug only the bottom two plugs.

Any assistance or feedback would be appreciated. I have trolled these forums quite a bit over the last two weeks, so if this problem has been covered on another tread I apologize.

Thanks in advance!
-Ben

No threats here, just plenty of help. Retiredcaps has an excellent thread on troubleshooting 'two seconds to black' problems.

What brand and series of cap did you use for replacements? Bad caps (failing, or junk) are a known cause of the problem.

Another possible cause is the CCFLs, and their associated wiring. One troubleshooting method is to substitute known good CCFLs (just hook them up to the inverter, no need to open the panel - yet.

PlainBill

[ben3843100]

Re: help to solve back display in 2sec

The capacitors used to repair the power board were a combination of Nichicon and Rubycon. Pictures of the inverter / power board are below.

Now that I've taken a second look at the video board, I see the capacitors on it are Samxon and Su'scon. Perhaps these require replacement as well.

[retiredcaps]

Re: help to solve back display in 2sec

Now that I've taken a second look at the video board, I see the capacitors on it are Samxon and Su'scon. Perhaps these require replacement as well.

Before changing any caps on the logic board, if you hookup a working computer displaying your favourite wallpaper, can you see the wallpaper by shining a flashlight onto the lcd screen?

[retiredcaps]

Re: help to solve back display in 2sec

Try this for the secondary inverter transformer test.

With power off and lcd unplugged, measure the resistance of secondary inverter transformer pins. If you have a manual range multimeter, set it to 2000 ohms.

Measure the ohms between the 2 yellow dots. Report measurement. Do the same for 2 red dots. They should be within 3% of each other.

[ben3843100]

Re: help to solve back display in 2sec

"measure the resistance of secondary inverter transformer pins. If you have a manual range multimeter, set it to 2000 ohms.
Measure the ohms between the 2 yellow dots. Report measurement. Do the same for 2 red dots. They should be within 3% of each other.

According to the measurements below, they seem to be reading within 3% of each other.

Yellow Dot Measurement: .609
Red Dot Measurement: .598

I reassembled the boards and plugged the LCD into a PC. I see my designated wallpaper for about 1-2 seconds, then nothing. I used a bright LED flashlight to look at the screen from multiple angles and didn't see a thing after the screen went dark. I did notice, however, that when you unplug the VGA cable with the power to the LCD on, the unit displays "no signal" without power cycling the screen. If you plug the VGA back in with the monitor powered on, it flashes my the wallpaper for 1-2 seconds and goes blank again.

[retiredcaps]

Re: help to solve back display in 2sec

Yellow Dot Measurement: .609
Red Dot Measurement: .598

If you plug the VGA back in with the monitor powered on, it flashes my the wallpaper for 1-2 seconds and goes blank again.

Your inverter transformers measurements suggest they are okay.

Since you see the wallpaper, the logic card is working fine.

This leaves the most likely candidate as the ccfl lamps and/or its wiring. See this photo album for examples of bad lamps or wiring.

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

[ben3843100]

Re: help to solve back display in 2sec

Your inverter transformers measurements suggest they are okay. Since you see the wallpaper, the logic card is working fine. This leaves the most likely candidate as the ccfl lamps and/or its wiring. See this photo album for examples of bad lamps or wiring.

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

I dissasembled the screen down the the CCFLs, compared them to the pictures in the above links, and read through the threads describing the inverter circuitry and how it has a built-in protection circuit that shuts down power to the lamps if there is a lamp problem. The lamps in the attached pic do seem dark on the ends. What do you think? New lamps?

Looks like these are two recommended links from other threads.
http://ccflwarehouse.com/blandovsp.html
http://ccfldirect.com/blowoutlamps.html

[retiredcaps]

Re: help to solve back display in 2sec

IThe lamps in the attached pic do seem dark on the ends. What do you think? New lamps?

The easiest way to verify is to use another lcd monitor to act as the "good" ccfl.

The 2nd one from the top looks like it is broken or cracked?

[ben3843100]

Re: help to solve back display in 2sec

The easiest way to verify is to use another lcd monitor to act as the "good" ccfl.

The 2nd one from the top looks like it is broken or cracked?

It does look cracked in the picture, now that you mention it, but I took a close look at it and it and it looks like it's in one piece. I do have an AOC 15-inch LCD that I could take apart for testing. I'll take a look at it tommorrow. I'm assuming I'll need to splice in two lamps (top or bottom plugs on the inverter board) for testing to complete the circuit. Thanks for the help.

-Ben

[retiredcaps]

Re: help to solve back display in 2sec

I'm assuming I'll need to splice in two lamps (top or bottom plugs on the inverter board) for testing to complete the circuit.

You don't need to splice in anything. Leave the ccfls in the AOC. Just stretch the cable from the "bad" monitor to one of the AOC "good" ccfls, but don't let the monitors touch.

Follow the instructions in the guide to determine which ccfl is bad.

[ben3843100]

Re: help to solve back display in 2sec

You don't need to splice in anything. Leave the ccfls in the AOC. Just stretch the cable from the "bad" monitor to one of the AOC "good" ccfls, but don't let the monitors touch. Follow the instructions in the guide to determine which ccfl is bad.

Update: I found a deal on a set of 4 CCFLs for this monitor, so I ordered them and am waiting for them to come in before moving ahead. I'll let you know how it works out after they're installed. In the mean time, I'll be troubleshooting my Westinghouse L2410NM.

-Ben

[ben3843100]

Re: help to solve back display in 2sec

Update: I found a deal on a set of 4 CCFLs for this monitor, so I ordered them and am waiting for them to come in before moving ahead. I'll let you know how it works out after they're installed. In the mean time, I'll be troubleshooting my Westinghouse L2410NM.

-Ben

Thanks for the troubleshooting help all. I received my 4 replacement CCFLs a couple days ago and soldered them in yesterday. The monitor is working great as you can see from the pics. It probably didn't need the power supply recap, but it was good practice. In all, it cost me about $35 dollars to fix this monitor for the new caps and 4 CCFLs plus shipping. It definitely takes patience to remove and reinstall the CCFLs on this model without damaging the wiring or bulbs.

-Ben

[retiredcaps]

Re: help to solve back display in 2sec

It definitely takes patience to remove and reinstall the CCFLs on this model without damaging the wiring or bulbs.

Good job. A few people have stumbled and broken their new replacement ccfls by rushing.