Why should you pay attention to the compatibility of spare screens!

Have you ever installed a new or refurbished original iPhone 7, 7+, 8 or 8+ LCD screen in your customer's phone to find that the touchscreen does not work? Or maybe everything was functional when you checked it, but your customer always comes back the next day saying that it has stopped working? You could simply think it is from the screen but it is not so easy.

Different manufacturers and different calibration settings.

Three companies manufacture LCD screens for iPhone 7 and 7+; LG, Toshiba and Sharp. Although the LCD screens themselves are manufactured to strict Apple specifications, compatibility between the iPhones varies widely. If you look at the serial number behind the backlight, there is a long serial code that doesn't seem to mean anything, but can be decoded as follows: The first three letters identify the manufacturer of the LCD and touch screen 3D and the remaining digits are the unique serial numbers on this LCD screen. 

If the iPhone has been calibrated for a Toshiba or Sharp LCD screen and you are performing a cross installation between these 2 manufacturers, there is approximately a 5% chance that the calibration will not be good. If the iPhone was originally calibrated for an LG LCD screen and you are performing a cross installation with a Toshiba or Sharp LCD screen, there is a 50% risk of tactile problems because LG's calibration sensitivity is very different from these 2 manufacturers. Without a calibration machine, you will have problems unless you install an LG LCD screen. it might be the reason why if you install an LCD you find touch problems, then install another LCD it works ! You will automatically assume that it was a bad LCD. However, it is possible that you have just changed the manufacturer and you were lucky as if you use the so-called bad LCD screen during the next repair, it will probably work without any problems!

Additional complications - Refurbished screens

To add other problems to the equation, it is not uncommon for reconditioners to replace the 3D touch panel of another LCD during a screen reconditioning. Damaging the flexible home button cable is very easy, especially on the iPhone 7 - Apple designed it to tear easily. If the LCD screen works, many recyclers would recover a good 3D touch screen from a bad LCD screen. It's great because they use an original Apple part instead of a Chinese copy, but if they have a Toshiba LCD screen and install an LG 3D touch screen, it can cause all kinds of problems.

It is said that if you keep the LCD and 3D touch screens the same, you should not have any problems unless you are working on an iPhone calibrated by LG. If you install an LG 3D touch screen on a Toshiba LCD screen, about 10% will not work. If you install a Toshiba 3D touch screen in an LG LCD screen, 60% will not work.

In summary

It is therefore very easy to assume that the LCD screen is defective as it has touch problems when installed on an iPhone. However, it is possible that external factors are causing the problem as you have seen.

It should therefore be observed that they are the first 3 letters behind the backlight of the screen to change to replace a screen of the same brand:

The factory codes are:

Toshiba : C11, F7C (preferably to be observed)
LG : DTP, CF3 (to be observed more strictly under penalty of having concerns)
Sharp ： DKH, C0N (preferably to be observed)