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Benq FP731 1st of 2 no backlight

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    #1

    Benq FP731 1st of 2 no backlight

    Getting most of the way through my pile 'o monitors to fix.
    Next up 1st of 2 Benq FP731s.

    My notes from when I first tested the batch, say no backlight. I *think* that means I could see an image with a flashlight, but I don't remember now.

    Silly assumption (I really must stop assuming) that I'd find bad solder, and bad 2sc5707s, so I disassembled and didn't do any voltage measurements.

    Surprise 1:
    All soldering (particularly inverter transformers) looks fine, even under magnification.

    Surprise 2:
    All 4 2SC5707s test fine out of circuit on a Peak analyzer. Figures, I have them in stock....

    Non-Surprise 1 Pico fuse PF751 is open. I *think* I got some of those with the 5707s from Ebay, hope so....

    Guess I'll replace the fuse and do some power-on measurements.
    More to come.....
    36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....
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    #2
    Re: Benq FP731 1st of 2 no backlight

    There are two more transistors on the board you should check. there number may be?FU9024N.
    Al.
    Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

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      #3
      Re: Benq FP731 1st of 2 no backlight

      I got some picofuses with C5707/FU9024 off ebay.

      I just fixed a FP731 and after checking everything carefully, all I did was change the picofuse and I'm using it now to write this.

      Originally posted by smason
      Non-Surprise 1 Pico fuse PF751 is open. I *think* I got some of those with the 5707s from Ebay, hope so....
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        #4
        Re: Benq FP731 1st of 2 no backlight

        Well I tested the other transistors in-circuit, none are shorted. Tested a few caps, they're in spec. Nothing else appears bad. Installed a new fuse (turns out I did get some with the transistors) and the monitor is up and going!

        2 down 2 to go
        36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

        Comment

          #5
          Re: Benq FP731 1st of 2 no backlight

          731 #2

          Opened up, inspected. Soldering looks fine, though someone may have been in here, a few joints have some flux.

          Tests, pico fuse, open. 2SC5707s 1 totally shorted, other 3 test ok. FETs test ok.
          Replaced all 4 5707s and the fuse, monitor working fine.

          Now for the Benq Q7c4 2 seconds to black..... Next week.
          36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

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