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This is the device page for the Samsung Galaxy J7. The OS that comes stock to the device is Android OS v5.1.

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Screen goes black after 2 hours of use, LCD works fine

Hi! I have a Samsung Galaxy J7 2016. I dropped for 2 seconds in water a week ago but I dissemble it and clean it. Everything went well for a week but now after extensive use, the screen goes black. It goes on again after a few attempts but goes black again. If I let my phone to rest for 2 hours, it works. Any ideas what is wrong with it?

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Hi @alin93 ,

How did you clean it?

Did you use Isopropyl Alcohol 99%+ (available from electronics parts stores) with a soft brush to gently brush away all traces of corrosion and water?

Did you remove any metal shields that may be covering components and check under them, as the water may have got in under them and corrosion is occurring there?

Did you disconnect all flex cables and clean the cable ends and the connectors as well with IPA?

These are just some of the things that have to be done when water comes into contact with electronic devices, especially those that have the power connected to them all the time, such as mobile phones.

Unless the battery is disconnected from the systemboard, there is always power available at certain points on the board, even when the phone is off, as the Power button is not a power isolating button. Think of the phone as being in an extremely low power state when it is off and not that it is totally disconnected from the battery.

Water, electricity and electronics are not a good mix. The impurities in the water creates corrosion and provides paths for the electricity that were not in the design of the phone and can damage the components. The corrosion starts immediately and is ongoing until it has been all correctly cleaned away.

Here’s a link that may be of some help. Electronics Water Damage

You may have to open it up again and check that you didn’t miss anything when cleaning

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Yes, I did everything you said but...I only cleaned the motherboard and all the connector cables, I didnt removed the touchscreen to check. I opened again and there is no corrosion. I think the cable connecting the LCD and motherboard may be overheating and I dont know why.


Hi @alin93

As I suggested it may be under the shields.

The LCD and touchscreen are integrated so if the problem was there you would have to replace the display assembly as a unit, LCD + digitizer (touchscreen)

As I DIY repair, without the schematics (I can't find any for the model) you can only temporarily replace the display assembly and check if the problem stays or goes.

If the problem is still there it is on the systemboard. If it now works OK it is in the display.

You could always try screen mirroring and check if there is a display when the screen turns black. I don't have a Samsung so not sure if this will work but worth a try maybe. If the external image stays on then the problem most likely is the display but maybe not. As I said I'm not sure how it works in your phone, but if it also fails then I'd say it is the systemboard


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Alin sarà eternamente grato.
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