Introduction

Have you ever installed an original refurbished iPhone 7, 7+, 8 or 8+ LCD into your customer’s phone only to find that the touch isn’t working? Or perhaps the touch was okay when you checked it, but your customer still comes back the next day saying it has stopped working? It’s easy to blame this problem on a faulty screen, but it may not be as simple as that.

Different Manufacturers- Different Calibration Settings

There are three companies who make LCDs for the iPhone 7 and 7+; LG, Toshiba, and Sharp. Although the LCDs themselves are made to Apple’s strict specification, compatibility between iPhone devices varies greatly. If you look at the 3D touch panel, there is a long serial code which might not look like it means anything but can be decoded to the following. The first three letters identify the maker of the LCD and 3D touch panel and the remaining digits are the serial- unique to that LCD. This information is also contained in the QR code on the back of the LCD and is recorded in Apple’s GSX server against the IMEI and the serial number of the device. This is one of the ways Apple can tell if the iPhone has ever had the LCD changed.

It would be fair to say that if Toshiba manufactured the LCD they would also manufacture the 3D touch panel that is attached to the LCD. This would be the same for LG and Sharp. When the iPhone is made in the factory and the first LCD is installed, Apple uses a special calibration machine to calibrate the iPhone to work with the LCD. We believe a similar machine is used if you ever take an iPhone direct to Apple for a screen replacement. At this point, it doesn’t matter whether the iPhone gets an LG, Toshiba or Sharp LCD as the calibration machine will make sure it is configured correctly. Where the problem occurs is when the screen is replaced by a 3rd party- who certainly won’t have access to the calibration machine.

If the iPhone was calibrated for a Toshiba or Sharp LCD and you cross install between these 2 manufacturers there is roughly a 5% chance of bad touch. If the iPhone was originally calibrated for an LG LCD and you cross install with a Toshiba or Sharp LCD then there is a 50% chance of touch problems because LG’s sensitivity range distribution is very different to these 2 manufacturers. Without having the magic calibration box to tell the iPhone you’ve installed a different manufacturer’s LCD you are going to have trouble unless you install an LG LCD. This probably explains why, if you install an LCD and experience touch problems, then install another LCD and it works, you’d automatically assume a bad LCD. However, it is possible you’ve just switched manufacturer and got lucky. If you used the suspected bad LCD in the next repair it would more than likely work with no issues.

Further Complications- Mixed and Matched Screens

To add further problems to the equation, it is not uncommon for refurbishers to replace the 3D touch panel from another LCD. It is very easy to damage the home button flex cable as- specifically on the iPhone 7- Apple has designed it so that it tears easily. If the LCD is working, many refurbishers would salvage a good 3D touch panel from a bad LCD. This is great because they’re using an original Apple part instead of a Chinese copy, but if they have a Toshiba LCD and install an LG 3D touch panel it can cause all sorts of problems.

It is said that if you keep the LCD and 3D touch panels the same you shouldn’t encounter any problems unless you’re working on an LG calibrated iPhone. If you install an LG 3D touch panel into a Toshiba LCD around 10% won’t work. If you install a Toshiba 3D touch panel into an LG LCD then 60% won’t work. Unfortunately, we don’t have any data for mixing Sharp LCDs or 3D touch panels.

Conclusion

So, in summary, it is very easy to assume the LCD is faulty because it has touch problems when it is installed in an iPhone. However, there is the possibility that external factors could be causing the issue. It would be prudent to try and swap the LCD on a like for like basis and match the 3 letter code. If you do experience touch problems with a refurbished LCD then before returning it as faulty, try it in your next repair and it may just work.

Toshiba LCDs and 3D touch panels start with C11 (left) or F7C (right).

LG LCDs and 3D touch panels start with DTP (left) or C3F (right).

Sharp LCDs and 3D touch panels start with DKH (above) or C0N (not shown).

Torn home button cable (left), separated 3D touch panel (right).