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Gateway LE1936

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    #1

    Gateway LE1936

    My Mom brought over her computer because of problems. I checked the monitor on my laptop and another computer and this is what I get.

    It will come on for about 15 seconds, then will turn off. When booting up her computer it would usually get to about the login screen for windows xp before it would turn off. The monitor doesn't stay on long enough for me to get to the menu with the exception of one time where I tried a reset.

    Problem: Will turn on for about 15 seconds or less, will go blank but blue light will stay solid. If I press the input button it will display no input, then when pressed again will come back on but be black within the 15 seconds. When it is on the brightness color changes a little bit.

    In doing some research I found one person suggested the logic board like it isn't detecting the signal. I found another post about the power supply capacitors, then one on here about bad transformers.

    I can get pictures later on, but need to know what would be best to get pictures of.. which board? I have a background in electronics doing electronics calibration but I know my knowledge is limited.

    No rush since she got a new monitor.

    Thanks
    Tags: None
    #2
    Re: Gateway LE1936

    Picture of both sides of the power board and the component side of the logic board.
    Attached Files

    Comment

      #3
      Re: Gateway LE1936

      If the Blue led stays on then the chances are that the Logic Board is ok.To narrow down where the fault is,there is two ways to do this...the first is to reconnect all the boards and screen back up,apply a signal from the PC,and then measure the voltage on the connector between the Power supply and Logic Board.the pins you are to measure between are the on/off pin and Gnd,and you will be lookinf for approx 3v DC,when the backlights are both on initailly and also when they are off,but the blue led still on.The second way is to connect the Power Supply ONLY to the mains and also plug in the backlights..NO other boards or screen connectors just the lamps and power supply,and then apply approx 3v Dc perhaps from a battery,betwen the on/off pin and ground,and see if the Lamps come on AND stay on or do the same as the fault symptom.If you have a 1kΩ resitor you can put that between the 5v supply which is on pin 1 or 2 of the same connector and the on/off pin instaed of the battery.Then advise.

      Comment

        #4
        Re: Gateway LE1936

        Originally posted by Rtech View Post
        If the Blue led stays on then the chances are that the Logic Board is ok.To narrow down where the fault is,there is two ways to do this...the first is to reconnect all the boards and screen back up,apply a signal from the PC,and then measure the voltage on the connector between the Power supply and Logic Board.the pins you are to measure between are the on/off pin and Gnd,and you will be lookinf for approx 3v DC,when the backlights are both on initailly and also when they are off,but the blue led still on.The second way is to connect the Power Supply ONLY to the mains and also plug in the backlights..NO other boards or screen connectors just the lamps and power supply,and then apply approx 3v Dc perhaps from a battery,betwen the on/off pin and ground,and see if the Lamps come on AND stay on or do the same as the fault symptom.If you have a 1kΩ resitor you can put that between the 5v supply which is on pin 1 or 2 of the same connector and the on/off pin instaed of the battery.Then advise.
        I was able to get a good solid reading with both the lamps on and when they turn off. Between pins 1 and 2 (ground and on/off) I get a solid 3.23 volts at all times.

        Comment

          #5
          Re: Gateway LE1936

          So the problem is the PSU/Inverter.Have you got any other good backlights around ??//as this is the easiest way to decide if the fault is the lamps or something else.Also What is printed on the top of the 2 Inverter transformers,as it not can not be made out from the photo ??
          Last edited by Rtech; 05-02-2013, 12:56 AM.

          Comment

            #6
            Re: Gateway LE1936

            Originally posted by Rtech View Post
            So the problem is the PSU/Inverter.Have you got any other good backlights around ??//as this is the easiest way to decide if the fault is the lamps or something else.Also What is printed on the top of the 2 Inverter transformers,as it not can not be made out from the photo ??
            T501: SPW-068 ROHS
            LSE K12AH

            T502: SPW-068 ROHS
            LSE K12AH

            In this case it appears the inverter transformers are the same. I do not have any backlights around.

            Comment

              #7
              Re: Gateway LE1936

              On the transformers,at one end of each is a pair of pins...measure the resistance,across each pair.

              Comment

                #8
                Re: Gateway LE1936

                Originally posted by Rtech View Post
                On the transformers,at one end of each is a pair of pins...measure the resistance,across each pair.
                Should I do it while they are in the board or out of the board? Going to be gone the weekend but will get measurements with em on the board.

                Comment

                  #9
                  Re: Gateway LE1936

                  Originally posted by Javve View Post
                  Should I do it while they are in the board or out of the board?
                  For the purposes of this test, in circuit readings will be fine. Obviously, power off and unplug the lcd.
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                  Comment

                    #10
                    Re: Gateway LE1936

                    Originally posted by Rtech View Post
                    On the transformers,at one end of each is a pair of pins...measure the resistance,across each pair.
                    Originally posted by retiredcaps View Post
                    For the purposes of this test, in circuit readings will be fine. Obviously, power off and unplug the lcd.
                    The pair of pins on the one end are pins 7 and 8, the other side has 6 pins, so I will measure across 7 and 8 as that's the only side with a pair

                    Meter at 2000 ohm range, leads shorted is 000 ohms, board disconnected and removed from case.

                    T501:
                    7 to 8: 619

                    T502:
                    7 to 8: 629

                    Comment

                      #11
                      Re: Gateway LE1936

                      You may have bad lamp assembly due to worn out lamps or burnt wire at the end of the lamp that is not making good contact after lamps are warm up.
                      Never stop learning
                      Basic LCD TV and Monitor troubleshooting guides.
                      http://www.badcaps.net/forum/showthr...956#post305956

                      Voltage Regulator (LDO) testing:
                      http://www.badcaps.net/forum/showthr...999#post300999

                      Inverter testing using old CFL:
                      http://www.badcaps.net/forum/showthr...er+testing+cfl

                      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                      http://s807.photobucket.com/user/budm/library/

                      TV Factory reset codes listing:
                      http://www.badcaps.net/forum/showthread.php?t=24809

                      Comment

                        #12
                        Re: Gateway LE1936

                        When testing do you have a source connected.

                        Try turning down the brightness a bit - does it stay on longer

                        If the lamp leads are long enough try swapping them.

                        Try and make a test bulb as link3 in budm's signature
                        Please upload pictures using attachment function when ask for help on the repair
                        http://www.badcaps.net/forum/showthread.php?t=39740

                        Comment

                          #13
                          Re: Gateway LE1936

                          The main causes of your problem now,would seem to be,wiring to the lamps or one or more faulty ones.Also each of the transaformers you measured have an associated 8 pin mosfet driving them(cannot see the number on them).One or both of them may be causing the problem.Also there are various resistors around the transformers and they need to be measured just in case.

                          Comment

                            #14
                            Re: Gateway LE1936

                            Originally posted by selldoor View Post
                            When testing do you have a source connected.

                            Try turning down the brightness a bit - does it stay on longer

                            If the lamp leads are long enough try swapping them.

                            Try and make a test bulb as link3 in budm's signature
                            I will have to look into the test lamp. When I tested for voltage at the beginning to check to see if it was the logic board or the power board, I had my laptop plugged into the monitor, and it was powered up, then tested again after the lamps turned off but the blue light was still on. That's when I got the approx 3 volts that showed the logic board was good.

                            Originally posted by Rtech View Post
                            The main causes of your problem now,would seem to be,wiring to the lamps or one or more faulty ones.Also each of the transaformers you measured have an associated 8 pin mosfet driving them(cannot see the number on them).One or both of them may be causing the problem.Also there are various resistors around the transformers and they need to be measured just in case.
                            I will check wiring to lamps, check the resistors, and check the fets. Will do a little digging to see what the fet testing procedure is. The Fet #'s are:

                            U501 and U502:
                            9971GD
                            620576

                            Comment

                              #15
                              Re: Gateway LE1936

                              Originally posted by Rtech View Post
                              The main causes of your problem now,would seem to be,wiring to the lamps or one or more faulty ones.Also each of the transaformers you measured have an associated 8 pin mosfet driving them(cannot see the number on them).One or both of them may be causing the problem.Also there are various resistors around the transformers and they need to be measured just in case.
                              Been busy. R501 and R503 are both 2M Ohm resistors. They measure 2.95 and 2.96 M-Ohms. They are a 5% tolerance resistor.

                              All other resistors in the area measured within the range of their stated value.

                              Haven't checked the IC's yet. Wondering if I should get a couple of 2 M-Ohm resisters that are closer to their stated value and see if that helps.

                              Comment

                                #16
                                Re: Gateway LE1936

                                I would de-solder one end of each resistor and measure again..

                                Comment

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