BenQ FP547 15" BLACK SCREEN

hello everyone.

trying to found the problem with my benq FP547 lcd monitor.

the problem started with black screen every few minutes . but soon become black permanent.
conecting to power and a signal, giving a green light (recognize the signal).

when starting with no VGA source, the back-light is turning on for few seconds. with the message "NO SOURCE" on screen.


checking the BLT_on voltage :

1)when starting, (no connection to vga source)- the green light is turning on for few seconds and the voltage is 3.3v as well (and then go to 0.0v).

2)when connection to vga source- the green light is turning on permanent- voltage is 0.0v. no back-light.



I changed 2 puffed cap's on the power board. with no chang.

checking the voltage on power bord:
the V-inverter is 13.3v (is that OK?). but no power is geting in to the 2 small transformers (cant see any Voltage after the fu9024n mosfet-[ Q751 and Q743 on the diagram]) .

I changed the 2 couple of transistors [Q759,Q760 & Q730,Q740 on diagram] (should be 2SC5706. but I got only the 2SC5707 that was available at store ) and replaced the 2 fu9024n mosfet. but no chang.

I'm working with the diagram, but don't have any clue what to do next.

any help or idea?





diagram url:

elektrotanya.com/benq_q5x3-304_power-bd_acer-547.pdf/download.html