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I'm repairing a HP 530 laptop with bad screen image. The image does not flicker, the corruption pattern is static.

If I connect an external monitor through the VGA port the image is fine, therefore I rule out the motherboard/GPU and I'm left with three components as the only suspects:

  • Flat cable
  • LCD inverter
  • LCD panel

Do you think I can rule out the inverter too? If I understand correctly what it does, if it fails I get no image at all, therefore a kind of on/off failure type.

I would rule out the flat cable too, I replaced it a million times on another laptop and it also causes a blank screen issue. Moreover, flat cable problems cause intermittent failure which depends on LCD hinge position too.

I could replace the inverter first and see what happens (it's cheaper than the screen) but I don't want to waste money if you can explain me how such failure cannot be caused by the inverter

Thank you

problem

inverter

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  • \$\begingroup\$ I don't think it's the inverter - but maybe get an o-scope on the output to check it isn't producing a stupid waveform that is somehow synced up to the lines on the screen. \$\endgroup\$
    – Andy aka
    Apr 7 '20 at 17:44
  • \$\begingroup\$ I too do not think it is the inverter. It's the controller or cable that causes every second line to go out. \$\endgroup\$
    – DKNguyen
    Apr 7 '20 at 17:44
  • \$\begingroup\$ I would rule out the inverter because of the way the image looks. This is a pixel-processing issue, so I would look at the chain of signal transmission. Try to squeeze the edges of the screen (carefully) or squeeze and move signal cable(s) to see if there is any change. There is a break somewhere on at least one signal line, but I cannot tell where for sure. It looks like a crack or break on the edge of the screen, possibly the ribbon disconnected from the screen in 1 or 2 spots. \$\endgroup\$ Apr 7 '20 at 17:48
  • \$\begingroup\$ Just because the VGA port works, doesn't mean there isn't something wrong on the LCD controller side. VGA and LCD are two very different protocols, they require specialized circuitry that may be bad for one, but OK for the other. \$\endgroup\$
    – Ron Beyer
    Apr 7 '20 at 17:59
  • \$\begingroup\$ @EdinFifić thank you, it makes sense to replace the ribbon first. After all it's the most stressed component in the chain. \$\endgroup\$
    – mfloris
    Apr 7 '20 at 17:59
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It is the LCD panel.

I bought an external controller model M.NT68676.2 that includes its own inverter and flat cable. I fed it the signal from a RaspberryPi and As you can see from the picture, the screen is corrupted the same way it looked when connected to the computer's motherboard.

enter image description here

And here's a picture of the setup, hope it helps.

image

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I think this is flat cable. Today, resolutions 1600x900 and 19200x1080 use odd and even lines. Оne of lines (odd or even) is broken. Some of other lines broken partially. Try to wrinkle the cable slightly. If image changing - it is а cable. Once I repared cable three times for good image.

Check the cable with a multimeter. Check RXEC+ (even clock plus) RXOC- RXEC+ RXEC- first (may be LCD have signs). When one clock pair is damage - picture in thin stripes. (1st line is even, 2st line is odd 3th line even etc) If check 8 RXЕ-lines and 8 RXO-lines is ok - then it's LCD panel.

The LCD inverter is OK. The damage to the inverter looks different than here.

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