I have this monitor and the picture goes black at very random intervals. I know it's not the signal from the PC because if I press the monitor power button the monitor comes back to life. Sometimes for a few minutes, sometimes for a few hours. I have read another post here that says it's the C5707 transistors and/or bad caps which causes the backlight to go out. I wouldn't say it's the backlight going out because: 1.) I do not see a ghosted image of the screen
2.) The power light goes completely out like the entire monitor is losing power, not just the backlight.
3.) The monitor doesn't go black instantaneously, it's like a slow 1 second pixelated fade (blue pixels) like the main power/voltage was dropping.
I am a electronic engineering technician by trade and am going to take it apart to fix it. Do the C5707 transistors provide power for the whole monitor or just the backlight? I would like to know which components supply power to the whole monitor as I'm guessing those are likely the problem.
There are 4 c5707/5706 in the inverter transformer driving circuits, the cause of the problem was due to poor solder connection in the bias circuits of the transistors. Make sure to check that after you install the new transistors otherwise you will blowthem up. Common problem with this model. When the circuit drwas too much power from the power supply, it will shut itself off to ptotect itself.
There are at least two version that I know of, it depends on who made them for DELL, in the beginning they were made by BEN-Q, and SAMSUNG, so soem of them use MOSFET for the inverter circuits, some use NPN transistor C5760/5707, they are not very big like the TO-220 case style mounting on the heat sink, it is only about .25" square with 3 legs. But always look for bad soldering works on these DELLS. Do you have picture of the board? [email protected]
The boards I work on alot look like this: http://www.electronicrepairguide.com/del...
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yeah based on pictures of 5707's I've seen, they are fairly large and robust, perhaps handling 5-10amps. I took the monitor apart and inspected the power supply board. There's no bad caps and the only devices that resemble the three leaded/anchored to heat sink style of voltage regulator like the c5707 are:
MBR10100ct
MBR20150ct
KIA278
I have no C5707/5706 components on either the power supply board or the processor board.
Funny thing is that now that i've taken the monitor completely apart, the problem has not come back. I either attribute that to:
1.) a bad/intermittent connection at one of the interface harnesses on the circuit boards
2.) Heat is no longer building up around the components like it may have when the monitor was assembled. Perhaps 10-20 degrees less makes the difference for the failing component.
Would appreciate anyone elses thoughts
yeah based on pictures of 5707's I've seen, they are fairly large and robust, perhaps handling 5-10amps. I took the monitor apart and inspected the power supply board. There's no bad caps and the only devices that resemble the three leaded/anchored to heat sink style of voltage regulator like the c5707 are:
MBR10100ct
MBR20150ct
KIA278
I have no C5707/5706 components on either the power supply board or the processor board.
Funny thing is that now that i've taken the monitor completely apart, the problem has not come back. I either attribute that to:
1.) a bad/intermittent connection at one of the interface harnesses on the circuit boards
2.) Heat is no longer building up around the components like it may have when the monitor was assembled. Perhaps 10-20 degrees less makes the difference for the failing component.
Would appreciate anyone elses thoughts
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