Month: August 2016

So, you repaired the backlight on your iphone 6, but the brightness doesn’t go fully bright anymore? You probably replaced the diode and maybe several of the big capacitors that make up the backlight circuit, right?

Does your iphone 6 look like this?

Backlight diode repaired on left — still dim; full bright iphone 6 on the right

We finally found a solution to this problem. The backlight coil is the problem. So, here are the steps that I take when diagnosing what’s at fault for an iphone 6 backlight problem:

1. Test backlight filters for continuity (FL2024, FL2025, & FL2026)
2. Test backlight capacitors for a short to ground or low resistance to ground (C1505, C1530, C1531)
3. Test backlight diode (D1501) in diode mode on multimeter (should be ~.2V one way and OL the other way).  If it reads 1.8V in one direction, then replace caps above and check again.  If it still reads 1.8V, then replace diode.
4. Test backlight coil (L1503) by putting multimeter in ohm mode on the anode side of the diode and C1597 or C1552 (first two caps in the row).  If it reads ~.6 ohms, then replace it.  A good coil should read ~1.0 ohm.
5. If voltage and resistance readings are still wrong above, then replace the backlight IC (U1502).

If you take the steps above, then all iphone 6 backlight problems will be resolved.  Here’s a video that I made of the repair on Youtube:

By now, we’ve all heard about the touch IC disease that has plagued the iPhone 6 plus. How about the iPhone 6S and 6S Plus Touch IC? How come we haven’t had any problems with touch IC disease on these newer iPhones? Well, the touch IC (Meson) on the 6S and 6S Plus is a newer chip (343S00014) that is built into the screen. It also serves an additional function, which is the 3D force touch. Now, every time the screen is replaced, the touch IC chip is also replaced. So there is no more touch IC disease in the newer iPhones.

Here are some pictures of the newer touch IC chip on the iphone 6s screen.  The chip is located at the top of the back of the screen.  Since this chip is located on the screen, it also means that if the force touch doesn’t work after a screen replacement, then it’s most likely the screen that is at fault.  A new screen should fix most touch and force touch problems.

iPhone 6S Plus touch IC chip is built-in to the display

iPhone 6S Plus Touch IC and Force Touch

It looks like the chip is held onto the screen with some pretty strong epoxy, so soldering a new chip on is probably not a very feasible thing to do.  With the iPhone 6S screens currently selling for around $100-$130 and the 6S Plus selling for around $160, replacing the chip is probably not very cost effective.  Replacing the screen would be faster, easier and cheaper.  I guess this spells the end of the touch IC disease as we know it. I’m pretty sure that something else will pop up in a few months, especially if it’s an iPhone.

If you have an iphone that doesn’t turn on and doesn’t draw any amps through the usb charging cable, then one of the first things that you should check is a short on PP_VCC_Main, which is the main power line for iphones. Here’s a picture:

In the ZXW Tools picture, you can test for a short on VCC_Main by flipping the logic board over (on an iphone 6) and put your multimeter in diode mode to test for continuity. Continuity testing is essentially testing to see if one point on a logic board is connected to another point via something metallic. If the two points are connected, then your multimeter usually beeps to signify continuity.

For a short, a beep is bad because it says that one of the components, like a capacitor or a resistor, is not doing it’s job correctly. It’s good for us repair technicians because it tells us that something is broken along that power line.

Here’s a short video of me finding a short to ground on PP_VCC_Main on an iphone 6 and resolving the problem through deductive reasoning.

Since there are so many components on the PP_VCC_Main power line, it’s not very efficient to test every component one by one. If you do that, then the time cost outweighs the cost of the repair, so you have to find ways to maximize efficiency, if you want to make money in this business.