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    #1

    Hp L1906 Monitor

    Received an HP L1906 - no power. Popped off the back and found several bulging caps. Recapped the power/inverter and power came on - but not backlights. LCD shows faint image - swapped lights to test and still nothing. Connector to logic board - brightness measured 2.67v, on-off 3.25v, 5.17v on 5v connection. Voltage measured near inverter is 24v. Where should I check next? Thanks
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    #2
    Re: Hp L1906 Monitor

    Originally posted by trwilson70 View Post
    Recapped the power/inverter and power came on - but not backlights.

    Where should I check next? Thanks
    If the backlights do not flash at all (even briefly), then it is likely you have shorted transistor or mosfet.

    Do all tests with power off and lcd unplugged. All tests can be done "in circuit". Set your multimeter to 200 ohms (if manual).

    For the yellow components, measure the resistance between pins 1-2, 1-3, and 2-3.

    For the red components, look up the part number and find its datasheet. Then test source-drain, source-gate, and gate-drain.

    Any reading under 30 ohms suggests a shorted component. To verify, desolder and retest.

    PS. Excellent clear focused pictures.
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      #3
      Re: Hp L1906 Monitor

      The 4 pin dip circled in the middle is the PWM IC for the inverter circuit. Don't worry about that.

      The driver transistors are the 4 pin dips closest to the inverter transformers.

      Get their part numbers and look up the data sheet for a pinout so you can test them.
      Elements of the past and the future combining to make something not quite as good as either.

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        #4
        Re: Hp L1906 Monitor

        Finally had time to sit down and check things out. Items in red, P607 BD6F2P at Q104 & Q105 - checked pin 1 to all other pins, the only pin that did not appear open was 1 to 3, 15 ohms on Q105, 33 ohms on Q105. Q102,103,106,107 Transistors, K-610 C945p - appear bad, measured resistance between E & C, don't think there should be any - B to C was able to measure both directions. Q101, 108, 109 Mosfets 2N7000 G08 - not sure how to test these - they are marked S-G-D - tried to energize not sure I have the correct type of meter - just reading resistance seemed they were all high. Anyway, with a little help on what to order I would replace the transistors and mosfets. Thanks

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          #5
          Re: Hp L1906 Monitor

          S-G-D S = Source G = Gate D = Drain

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            #6
            Re: Hp L1906 Monitor

            Originally posted by trwilson70 View Post
            Finally had time to sit down and check things out. Items in red, P607 BD6F2P at Q104 & Q105 - checked pin 1 to all other pins, the only pin that did not appear open was 1 to 3, 15 ohms on Q105, 33 ohms on Q105. Q102,103,106,107 Transistors, K-610 C945p - appear bad, measured resistance between E & C, don't think there should be any - B to C was able to measure both directions. Q101, 108, 109 Mosfets 2N7000 G08 - not sure how to test these - they are marked S-G-D - tried to energize not sure I have the correct type of meter - just reading resistance seemed they were all high. Anyway, with a little help on what to order I would replace the transistors and mosfets. Thanks
            What are the numbers on Q104,andQ105?
            Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

            Comment

              #7
              Re: Hp L1906 Monitor

              Q104 & Q105 are marked P607, BD6F2P. Thanks

              Comment

                #8
                Re: Hp L1906 Monitor

                If you are looking for those, search Aop607
                Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                Comment

                  #9
                  Re: Hp L1906 Monitor

                  Thanks - how about the transistors and MOSFET's. Where's the best place to try to learn/translate the numbers/markings? I pulled up the data sheet on C945p transistor but don't totally understand all the terms to then order the correct thing from Digi-Key - but did give it a shot. Thanks

                  Comment

                    #10
                    Re: Hp L1906 Monitor

                    Use findchips.com
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                    We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

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                    Comment

                      #11
                      Re: Hp L1906 Monitor

                      Thank you, that does help. The only source for the transistor lists them at $9.00 each - can they really be that much?

                      Comment

                        #12
                        Re: Hp L1906 Monitor

                        i love ebay sometimes..

                        http://cgi.ebay.com/220422965955
                        http://desc.shop.ebay.com/i.html?_nk...LH_TitleDesc=1

                        Comment

                          #13
                          Re: Hp L1906 Monitor

                          You can purchase the C945 from a number of sources. You can order 1 or 2 from the large parts houses for approx 10 cents each and pay $8.00 S/H or go to ebay and purchase a 100 for $3.00 w/ free ship!

                          http://shop.ebay.com/?_from=R40&_trksid=m570&_nkw=c945

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