There's nothing that obvious when looking for dry/cracked joints. and L781 looks good from here....Of course I'm not a regular at soldering, but this doesn't seem to be my problem. (mine went white after cofiguring a new PC, now it turns white on all PCs..) Maybe it was directly related to the new video card...
I took the monitor to an experienced technician in the medical field (repairs bio-medical equipment of all kinds) He picked out a few "blobs" of solder as well as went over the L781 inductor someone out here mentioned. It now WORKS PERFECTLY, no more white screen and I immediately got my self test display when I turned it on. THANK YOU fixya and all those who posted. I just saved $200 on a new display.
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Re: Case open, looking for bad solder
This is how to check what's wrong with your LCD monitors. Firstly, power on both CPU and monitor.
After it went white, you have to check that if you can see the image on the
screen or not by shining a flashlight into the screen, not directly but find the best
angle to the screen and take a look very closely. If you can see the icons or
any image, there will be a minor problem. Like me, I can see window image using
flashlight and check lamps inside. Some of them were broken and it is easily
replaced. If you cannot see anything on the screen, there'll be some problems
with inverter board. If you have soldering tool and want to fix it by yourself,
check the caps first. It may cause this problem. Some caps might show leaking
or burn spot on the board because of too high temp. If you don't have soldering
tool, you better go get a technician to do so.
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Failed capacitors on main board.could be dry joints...quick way to find out is open back after disconnecting from mains.look for any swollen..split or burnt capacitors...these are black with silver tops...
tutorials on YouTube....if it's just dry joints then as they warm up the solder joint disconnects thus resulting in shutdown.try tip of solder iron on all the connections that look suspect.usually telltale signs are brown flux seepage and cracked solder around connections.
Sometimes our electronics appliances like TV monitor, radio or any other stuff may have a very simple problem. If we are not aware of this then we go in circles looking for the problem.<br />Technicians sometimes refer to this as intermittent problem. Sometimes the system will work and sometimes it will not. A tap/knock may get it working or will stop it from working.<br />Dry-solder joint is one of the causes.<br />If you are a novice and have no idea about electronics and how to work with soldering irons and electricity; please get assistance from a professional.<br />1. Switch off power.<br />2. Open the system up.<br />3. Discharge components which might hold charge to avoid electric shock.<br />4. Look at the bottom of the printed circuit board (track side of the PCB). You might need a hand lens for a closer look.<br />5. Look for cracks in the soldered components. Sometimes shaking components easily helps in identifying these cracks.<br />6. Once you get to know this, get your soldering iron, remove the old solder and re-solder the component.<br />7. You might be agitated to switch on and check your system at this point in time. Don't!!<br />8. Try and look for all the dry solder joints.<br />9. Fix as much dry solder joints as you can find.<br />10. Clean your board. Use isopropyl or general purpose thinner.<br />11. Double check the track side. There should not be any shorts that you may accidently done while soldering.<br />12. Once you are sure all is safe, assemble the system.<br />13. Connect a <span>series lamp</span> to the system and switch on to check.<br />14. If the problem stops; good for you. If it persists then continue looking for and treating dry solder joints.<br /><br />I will share more on series lamps in my next tip.<br /><br />Enjoy<br />Rjn<br /><br />
Poor solder joints are seen under a magnifying glass study some solder joint they look like a drop of water frozen in the up position with a wire pin in the middle smooth and shiny. now a bad one will have a crack in the up ward portion of the solder. good luck.
Your problem is caused by dry joints and cold solder on the board. If you have a soldering iron and soldering lead open the back panel of your tv. Look for dry joints around the board especially on the power supply section.Cold solder is hard to spot, it is necessary that your working area have sufficient source of light or you may use a table lamp.
Hope it may help you.
Have a nice day!
Thanks for using Fixya.
This is a warm up issue and can probably best be found by using circuit cooler on suspected components.
Other possible problems may be a bad solder joint or cracked circuit board.
Candle the board with a bright light to look for cracks.
Bad solder joints take experience to spot, but pay particular attention where panel mounted volume controls solder to the circuit board. Looking for the little ring around the solder menicus takes a sharp eye and good lighting. Resolder any suspected bad joints.
sounds like you have bad solder joints,some may have hairline cracks in them from overheating and you may just have to have it serviced.You can open it up and look for bad solder spots and remove the solder with solder wick and resolder it with some good solder.most places use led free solder which doesn't seem to with stand the heat.
It may be worth doing some basic checks - look for a dry or fatigued solder joint on the blue video driver output circuit - look for a bad joint at any pcb plug or socket connection on the video amp board and the CRT connection PCB.
If nothing is obvious, toss it - put the repair shop cost towards a new one.
I also tried re-soldering joint L781 on the main power control board (see Solutions #2 and #7). It worked. My 15 inch Dell flat panel LCD is working again, white screen gone. The solder around the pin did looked different to to the other joints...a very slight gap around the pin as though it wasn't contacting properly. To locate L781, look at the bottom of the PCB (the side with the soldering) with the power plug socket at the edge closest to you. L781 is in the top left quadrant of the board, about 2 inches in from left, 1 inch down from the top. For good measure, I also tried the solution that suggested trimming a millimeter of the end of the two data ribbons that plug into the smaller control board, although I couldn't see anything wrong with the data ribbons. I did this at the same time as resoldering L781 so not sure if it made any difference.
i also suspect its just bad solder connections, the vert. o/p ic is maked ic451 look for all the ic's on heatsinks. it should have 10 to 15 pin all in a straight line & be attached to a small heatsink. if i remember right i think if you are looking at the tv from the back it is on the left side near the front (by the buttons/swtitches). resolder all the pins on the ic & resolder the parts just around the ic as they too also develop bad solder connections. just remember to check for shorted pins after soldering. good luck.