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Crumbtrail TV Forums: TV Equipment: LCD TV Forum:
LCD monitor fades out after a dew seconds

 

 


Dick G
New User

Sep 2, 2014, 8:14 PM

Post #1 of 8 (2281 views)
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LCD monitor fades out after a dew seconds Can't Post

I have a Samsung 2253LW LCD monitor I have been using for some time. It suddenly starting going black a few seconds after turning on. The display is good for about 4-5 seconds. It appears the picture is changing, because if
I turn the monitor off and then on again, the display has changed depending on what I am doing, but it immediately goes dark again. Switching on and off always brings it back for a few seconds. I checked the lytics and found 2 bulging ones, which I changed. I put it back together and still had the same problem. I do not have a schematic, which would be helpful. Any idea what this problem might be??



jts1957
Veteran


Sep 2, 2014, 8:47 PM

Post #2 of 8 (2277 views)
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Re: [Dick G] LCD monitor fades out after a dew seconds [In reply to] Can't Post

Same unit?
http://www.tv-forums.com/...?post=157641;#157641


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Location: Far, Far Away


Dick G
New User

Sep 2, 2014, 10:07 PM

Post #3 of 8 (2271 views)
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Re: [jts1957] LCD monitor fades out after a dew seconds [In reply to] Can't Post

Yes, it is the same unit. I bought the capacitors and a new cable and put it together again. Still had the same problem. I do not see anything else that might be defective on the board.


jts1957
Veteran


Sep 2, 2014, 10:39 PM

Post #4 of 8 (2269 views)
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Re: [Dick G] LCD monitor fades out after a dew seconds [In reply to] Can't Post

Self-Test Feature Check
1. Turn off both your computer and the monitor.
2. Unplug the video cable from the back of the computer.
3. Turn on the monitor.
If the monitor is functioning properly, you will see a box in the illustration below.
This box appears during normal operation if the video cable becomes disconnected or damaged.
4. Turn off your monitor and reconnect the video cable; then turn on both your computer and the
monitor.
If your monitor screen remains blank after using the previous procedure, check your video controller
and computer system; your monitor is functioning properly.


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Location: Far, Far Away


Dick G
New User

Sep 2, 2014, 10:50 PM

Post #5 of 8 (2266 views)
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Re: [jts1957] LCD monitor fades out after a dew seconds [In reply to] Can't Post

I should have added that I tried a different monitor on this
computer and it worked fine. I tried my defective monitor on another computer and it displayed the same problem.
Something seems to be sapping the voltage. If I turn the bad monitor off and on the picture comes back for 3-4 seconds. If I print something on the screen it is obviously being outputted, you just can't see it. It behaves like a leaky electrolytic, but (except for the two I changed) they check good with an ohmmeter. Could it be something in
the screen section and not the circuit board? Don't know if there are any caps in there. I have it all apart on the table at this point.


jts1957
Veteran


Sep 2, 2014, 11:09 PM

Post #6 of 8 (2264 views)
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Re: [Dick G] LCD monitor fades out after a dew seconds [In reply to] Can't Post

Bad CCFL bulb(s) (or connection(s)). Swap for test bulbs or use test jig to drive bulbs in yours.
OR
Bad HV Transformer(s) (or connections). Ohm out various windings. Compare same winding on one transformer to another.
OR
Bad driver(s) for HV Transformer(s).
OR
Feedback/Sensing circuitry for CCFL bulb balance correctly (or incorrectly) functioning.
OR
Enable (from Scaler board) starts out active, but cuts out. DVM
OR
B-Plus starts out present, but for some reason leaves. DVM

Edit: Even though not bulged, could still have a defective capacitor in/on power supply/inverter.


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Location: Far, Far Away

(This post was edited by jts1957 on Sep 3, 2014, 2:24 PM)


Dick G
New User

Sep 3, 2014, 2:06 PM

Post #7 of 8 (2250 views)
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Re: [jts1957] LCD monitor fades out after a dew seconds [In reply to] Can't Post

Thank you for the advice. Much appreciated. I will look into the things you suggested as possible problems and again post when I have done so.


Dick G
New User

Sep 5, 2014, 4:04 AM

Post #8 of 8 (2234 views)
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Re: [Dick G] LCD monitor fades out after a dew seconds [In reply to] Can't Post

I am posting an update, but am still fighting the problem.
I managed to get a service manual with some schematics. I checked out voltages on the circuit boards and they seem to be OK. Information is sparse on the inverter outputs that feed the four individual wires going into the panel.
They are supposed to feed current to the lamps. I do not read any voltages on them. not sure how to check the bulbs in the panel, but will google as you suggested.
Thanks

 
 
 


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