BENQ FP7G+ black screen with green led

[joeh]

hI friends I have a problem with my monitor benq FP71G +. The problem is that power can not display anything on the screen (totally black screen) and the green light remains fixed even after several minutes, the same as if I remove the vga cable between the monitor and PC, after a while it becomes orange as it should be in case of no signal.
Opening the monitor, the power supply board is as follows 48.L1C02.A13

HELP

[dj_ricoh]

Re: BENQ FP7G+ black screen with green led

Did you check the fuse? whats the V on the big cap? do you got 400? its a 400V cap right?

[joeh]

Re: BENQ FP7G+ black screen with green led

The fuse i ok, the cap is 450v

[dj_ricoh]

Re: BENQ FP7G+ black screen with green led

450v when you power it up, thats the value that you measure?

[budm]

Re: BENQ FP7G+ black screen with green led

OK, check the fuse as shown in the picture, it is for feeding B+ to the inverter Royer Oscillator circuits for driving the Inverter transformers. Put meter's black lead to the chassis, hen use the Red lead to check the voltage on both ends of the fuse.
You may have bad transistors/MOSFETs as shown as which need to be checked for short.
Right now the 5V for the logic board is working.
It can also be that the logic board is not sending out the BL_ON signal to turn on the inverter circuits.

[Lumberjack777]

Re: BENQ FP7G+ black screen with green led

A common problem with the BenQ's is that the transistor(s) near the inverter transformers short out. The part number is usually like C5707 or C5706. I circled them in red on the left side of the board. Occasionally the one circled in the middle of the board will short out also. And also check the pico fuse circled in blue.