Accidental overvoltage - any repair suggestions?

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1

I accidentally applied near 12v to the 5v input of my Nextion 4.3" enhanced… twice!
Yes I burned 2 screens… my buck regulator circuit puts out 5v most of the time, but occasionally puts out 12v… resulting in this damage.
Im back on a reliable 5v source now, and trying to repair my screens.
Both screens respond to serial messages, so something is working, but the display is dead.
I have checked U7, the linear regulator close to the power input.
It is still putting out 3.3v.

Can anyone suggest anything else I can try to repair these 2 screens?

Model number NX4827K043_011.

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2

Possible dead gpu. Check it

3

There is no GPU on this Nextion HMI. Just a LCD driver IC. But since the 3.3V are intact, I’d say it has survived.
I’d rather look into the backlight boost converter. But in general, with a minimum of self-esteem, your working time to diagnose and fix it will be more expensive than buying new and reliable stuff.

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4

I had the same fault and that was it, I also received voltage but the ic got very hot

5

In the end, it was one of the backlight LEDs was burned, disabling all of them. My assistant was able to patch it by shorting out the bad led, and the rest were still ok. One part of the screen is slightly dimmer than the rest, so we cant use it for production, but we will keep it for test rigs.

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6

Hi , New to this forum, looking forward to learning from you all,
I have the same issue as michael_1,
The Nextion (NX8048K050_011 actually still functions including touch BUT the LCD is blank!
Please Help !!
I’d really like to know how your unit was repaired.
Does anyone have a schematic for this screen ?
I’d love to be able to fix it,
It’s a unbelievable that these Nextion screens have no power protection circuitry, the company is aware of the issues people are having.
Regards

7

If you look along the edge of the screen, right under the glass, there is a metal surround with perforations where it all clips together. Use a tiny screwdriver or tweezers to pry these clips apart, and you will find a thin cavity behind the liquid crystal (which is attached to the glass). Around the edge of the cavity are white LEDs that shine on the back of the cavity, creatind an even spread of white backlight. If you hold the glass up to a bright light, you may see your screen data, very faintly. One or more of the backlight LEDs are blown, and they are in series, so they all stop working. If you short them out one by one with your tweezers, when you find the bad one, the others will all light up. Then you can choose to either replace it, or solder a wire over it, permanently shorting it out, leaving a barely noticeable dim region on your screen. We have done this twice and each time it worked the same.

8

Thanks very much, I’ll give it a go,
cheers

9

Hi,
Sadly after delicately dismantling the LDC and checking all the Leds, I didn’t find any that were faulty.
I managed to faintly light up each LED in succession by using the Diode setting on my meter.
I was really keeping my fingers crossed hoping that this would be a dream fix, not to be :frowning:
If anyone has any other ideas I be happy to hear them.
Thanks for your time
Regards