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drjaydenm
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Last Activity: 08-19-2019, 08:00 PM
Joined: 08-02-2018
Location: Queensland
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  • drjaydenm
    replied to Dell U2713Hb No Display
    in Troubleshooting Computer Displays
    Re: Dell U2713Hb No Display

    So I managed to get the monitor up and going and everything seems to work now.

    I spent hours and hours probing that logic board, but couldn't find what was wrong with it - I also couldn't work out what the codes in the logs posted above mean, they could have been the key I feel.

    I ended up buying a new logic board for $45 USD and it fixed the issue! I felt it was worth it as an equivalent monitor is still worth a few hundred dollars. This was a great learning project where I've leant a lot, but the problem was above...
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  • drjaydenm
    replied to Dell U2713Hb No Display
    in Troubleshooting Computer Displays
    Re: Dell U2713Hb No Display

    Thanks for explaining that part of the circuit, it makes sense now. It turns out I was turning on the wrong gate which caused the ground gate to open too No wonder it was shorting... lucky I didn't wreck anything!

    As I can't see any other problems with components at this stage, I've hooked up to the debug UART serial port and got the following logs out on startup from the STDP9320-BB chip.



    The line looks interesting to me, although I have no idea what it means...

    Budm, do you have...
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  • drjaydenm
    replied to Dell U2713Hb No Display
    in Troubleshooting Computer Displays
    Re: Dell U2713Hb No Display

    That was all tested with the timing controller board disconnected - the scaler board is connected straight to the bench supply, bypassing the SMPS too. The regulator usually outputs 12V, even if the input is a bit higher at 12.6V (that's what the monitor SMPS was outputting). It consumes 0.233A in standby which I am guessing is mainly the CPU. During this period, I've had it running for hours with no heat apart from the usual CPU heatsink.

    Once the MOSFET is manually switched on by temporarily brining the gate voltage down, it stays on. The...
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    Last edited by drjaydenm; 10-02-2018, 03:14 PM.

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  • drjaydenm
    replied to Dell U2713Hb No Display
    in Troubleshooting Computer Displays
    Re: Dell U2713Hb No Display

    I may have narrowed down the problem - still not sure if it is the problem, or just a side-effect though.

    On the logic board, the LVDS power circuit is off in standby mode. Brining the MOSFET gate down (highlighted in image) to ground for a second starts it up, but then something shorts which brings the whole circuit down to 7V from 12V and chews 1.5A. The voltage regulator ground gets very hot after a while. Could the voltage regulator be bad? Or is the heat due to the short elsewhere? I can't find anywhere else on the board that gets...
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  • drjaydenm
    replied to Dell U2713Hb won't power on.
    in Troubleshooting Computer Displays
    Re: Dell U2713Hb won't power on.

    Hi all, have any of you made any progress?

    I've got the same monitor and have a thread going here [URL="https://www.badcaps.net/forum/showthread.php?t=71459"]https://www.badcaps.net/forum/showthread.php?t=71459[/URL] with lots of images if it helps anyone.

    I'm suspecting IC532 might be bad as well - the ground terminal heats up quite a lot when manually running the board with a bench supply. Has anyone replaced this and got it working?Re: Dell U2713Hb won't power on.

    Hi all, have any of you made
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  • drjaydenm
    replied to Dell U2713Hb No Display
    in Troubleshooting Computer Displays
    Re: Dell U2713Hb No Display

    Forgot to mention that I pulled the heatsink off the CPU to check the model. Turned out to be model STDP9320-BB. I can only find a databrief sheet though, so not much help.

    It is strange, it looks like the CPU gets the input for power on, but does not output the PS_ON signal. Is there a way to check if the CPU is working at all?...
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  • drjaydenm
    replied to Dell U2713Hb No Display
    in Troubleshooting Computer Displays
    Re: Dell U2713Hb No Display

    I have traced back both the power button and PS_ON connector to the CPU on the logic board. There is 0V on the PS_ON (CN1/12) wire both before and after the power button is pressed. There aren't any opens along this path. Everything seems OK here.

    On the power button side (J12/1, J12/2), J12/2 sits at 2.56V and gets grounded to 0V when pressed. However TP_Unamed (next to R176) shows 0.82V potential when the button is pressed.
    Is this going to cause issues with the CPU identifying the button is pulled to ground?...
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  • drjaydenm
    replied to Dell U2713Hb No Display
    in Troubleshooting Computer Displays
    Re: Dell U2713Hb No Display

    Thanks, I'll start working on the logic board and see if anything is going wrong there.

    I measured the filter cap and it was at 400VDC when the power was first turned on, then went down to 320VDC over about 10 seconds and sat there.
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  • drjaydenm
    replied to Dell U2713Hb No Display
    in Troubleshooting Computer Displays
    Re: Dell U2713Hb No Display

    Here's a schematic for the LED power supply area involving the 4 wires - pins 10-13 (blue, orange, purple, white) coming from the main board.

    It looks like pins 10 and 12 aren't connected to anything (missing resistors or caps that were never soldered on).

    Do the labels of on/off and brightness for those lines look correct here? If that is correct, then I will start tracing pin 13 through the main board....
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  • drjaydenm
    replied to Dell U2713Hb No Display
    in Troubleshooting Computer Displays
    Re: Dell U2713Hb No Display

    After more checks on the LED back light, I've probed each pin and I get the following voltages on the connector:[LIST=1][*]0V[*]0V[*]33.1V[*]33.1V[*]0V[*]0V[*]0V[*]0V[*]33.1V[*]33.1V[*]0V[*]0V[/LIST]

    I've found the datasheet for this model of panel [URL="https://www.dropbox.com/s/qvb1owwydn9bux5/Panel_LG_Display_LM270WQ3-SLA1_0.pdf?dl=0"]https://www.dropbox.com/s/qvb1owwydn9bux5/Panel_LG_Display_LM270WQ3-SLA1_0.pdf?dl=0[/URL]

    Two questions that I'm trying to answer now:[LIST=1][*]On page 7 it states that the voltage...
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    Last edited by drjaydenm; 09-01-2018, 02:03 AM.

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  • drjaydenm
    replied to Dell U2713Hb No Display
    in Troubleshooting Computer Displays
    Re: Dell U2713Hb No Display

    I am seeing 12.6Vdc on all four red cables in the main board connector. The 2 black and 2 brown cables are both grounded. The other 4 coloured cables all show 0Vdc. Is it normal that all four red cables would be live without the power button being pressed?
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  • drjaydenm
    replied to Dell U2713Hb No Display
    in Troubleshooting Computer Displays
    Re: Dell U2713Hb No Display



    [B]So if you toggle the power switch, do other touch buttons' light go on and off when power switch toggle?[/B]
    The touch buttons light up as soon as the monitor is plugged in and you touch one of them - irregardless of the power button. Pressing the power button then has no effect - the buttons stay lit up.

    [B]'it can be that the BL-On signal from the logic board is not present, or the Boost converter is not working, etc.'[/B]
    How do I go about diagnosing the BL-On signal? Which wire would that be sent across...
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  • drjaydenm
    replied to Dell U2713Hb No Display
    in Troubleshooting Computer Displays
    Re: Dell U2713Hb No Display

    Thanks for the guidance. I've checked the voltage of that brown cap and it is sitting at 33.3V - even when the monitor has just been plugged in without the power button being pressed.

    However whilst doing that, I noticed the power LED doesn't light up after pressing the power button - but the other touch buttons all light up. I checked the buttons ribbon cable was seated correctly and can see 0R over the two power wires on the ribbon when the button is held in - so I would think it should be sending the signal to turn on.

    Whilst...
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  • drjaydenm
    replied to Dell U2713Hb No Display
    in Troubleshooting Computer Displays
    Re: Dell U2713Hb No Display

    I forgot to mention what I have tried so far:[LIST][*]Re-seating all connectors and reassembling - no difference[*]Powering on without the USB board - also no difference[*]Testing ESR for electrolytics using the Blue ESR meter in-circuit. There were no outstanding ESR values - even on the suspect USB caps[*]The 250V fuse is OK. The 3A fuse on the logic board is also OK[/LIST]
    • Re: Dell U2713Hb No Display

      I forgot to mention what I have tried so far:[LIST]
    • Re-seating all connectors and reassembling - no difference
    • Powering on without the
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    Last edited by drjaydenm; 08-25-2018, 07:42 AM.

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  • drjaydenm
    started a topic Dell U2713Hb No Display
    in Troubleshooting Computer Displays

    Dell U2713Hb No Display

    Hi all, I've recently got a hold of a broken Dell U2713Hb monitor and am trying to diagnose the issue and fix it. Unfortunately it's just outside of it's warranty.

    The symptoms are that when the power button is pressed, the power light comes on, but there is no display (no display and no backlight). When the other touch buttons are pressed, they all light up and stay lit up until the monitor is powered off.
    I have been told by the previous owner that the USB ports on the side were used to charge a mobile phone daily. I checked out the USB board and it does look to have some...
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    Last edited by drjaydenm; 08-25-2018, 07:28 AM.
  • drjaydenm
    replied to New Members - please post your introductions here
    in Announcements & Related News
    Re: New Members - please post your introductions here

    Hello from Australia, just hoping to learn some more and maybe fix up a monitor I have lying around.
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