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| Galaxy S7 No Image | |
|---|---|
| Device | Galaxy S7 |
| Affects part(s) | Motherboard, Display |
| Needs equipment | Microscope, Multimeter |
| Difficulty | ◉◉◉◌ Hard |
| Type | Soldering |
Problem description
The device turns on but no image is display on the screen.
Symptoms
- Device turns on but no image is displayed.
Solution
There can be 2 causes for no display on this device a bad screen or a motherboard fault.
Diagnostic Steps
The first step is to always start with the basics try a new display before assuming you have a faulty motherboard.
If a new display fixes the issue then all that is needed is a screen replacement.
If a new display does not fix the issue then we confirm the problem is on the motherboard.
The first step is to do a visual inspection of the motherboard under the microscope especially near the display FPC, look for any water damaged, burned components, and physical damage like a ripped component.
The next thing that should be done if nothing is found damaged is to measure diode readings on the components next to the display PMIC it common to have a short here.
When taking diode readings of the FPC, if you measure a line that should read, for example, 0.500V but get 0.100V or 0.000V, it indicates a short on that line. The best way to trace the short is to inject voltage into the line with a DCPS and use a thermal camera to identify which component heats up. Fallow this guide how to find the short Short Circuits - Repair Basics the small ic will most likely be the issue.
If you measure a line that should read 0.500V but get OL (Open Line), it indicates a disconnection in the circuit. To trace the issue, consult the board view to follow the line’s path.
If everything looks ok here next thing to do is to check if 2 important voltages are present, if any these voltages are not present replace the small display PMIC.
Repair Steps
If by replacing by trying a new display the image fault is solved all you have to do its to replace the display.
If there is a any physical damage to the FPC the solution is to replace it. The best method is to use a hot air station to desolder the old FPC, clean the old solder from the motherboard, apply new solder, align the new FPC, and use the hot air station to solder it. Be careful not to use excessive heat, as you may cause a solder bridge under the motherboard.
When taking diode readings of the FPC, if you measure a line that should read, for example, 0.500V but get 0.100V or 0.000V, it indicates a short on that line. The best way to trace the short is to inject voltage into the line with a DCPS and use a thermal camera to identify which component heats up. Fallow this guide how to find the short Short Circuits - Repair Basics
If you measure a line that should read 0.500V but get OL (Open Line), it indicates a disconnection in the circuit. To trace the issue, consult the board view to follow the line’s path.
If the PMIC is shorted the soluction is to replace it, this chip is a MAX77838 and can be found online and is not expensive the chip is also used on the Galaxy S8.
This is a BGA chip and must be replaced using a hot air station, the new ic ussualy comes reballed.
Final Testing
After assembling the phone, ensure every function is working as expected, not just the display.