Samsung P2250 computer monitor repair

[tiv48]

I would not normally get involved in the repair of flat screen tv's or monitors but this one belonged to my brother .
The problem was that the back light would only come on for 1 second.
A quick search on google suggested that power supply caps would be the problem.
After a fight to get it apart (no screws here) i removed the power board and checked all the caps on the secondary side (there are only 5)
of coarse the were all ok both value and ers .
a close inspection of the board showed a scorched area of board by the inverter transformer , on the back side of the board  i found 4 smd resistors in series all were 56k  and although they all read ok they had obviously suffered from heat .
I do not have any smd devices but i did have a 220k 1 watt resistor so i took one of the sm resistors off and wired the normal resistor in place
(the 4 smd resistors  were marked R39) this is a revision 1 board .
this cured the problem and looks like it may become a common fault.
sorry no photos as i did not have a charged camera handy.
Rob T

[Nick]

Oddly, I'm dealing with something similar at the moment... comes on for 1 second or less, then goes dark... however, on looking closely in a decent light, you can see that the LCD is actually working...

We have panels of LG 55" monitors in 2x2 matrixes - one panel of one of the grids has failed - they are not made any more and replacing all 4 will cost USD 4,000... (can't replace one with a different make or model - it'd look wierd).

So, I swapped the PSU from the failed panel with a known good one from one of the others. No change. Likewise, swapped over the CPU board (there are only two boards in these things). No change.

The LCD itself seems to be working, but the backlight has failed.

On these screens, the backlights are strips of LEDs - I found a kit one eBay for about USD 25 - this is a very common fault generally with many makes and so bits are always available.

Moral: Don't assume it's the PSU board (though it may be) - the LEDs/CFL backlight could be the culprit...

[tiv48]

I believe that LED back lights are be default over run.
A friend of mine who does repair these things always suggests to the customer that they turn the back lighting down a bit to extend the life of the LEDS.
Rob T