Iphone 6 image issue

[keypuncher]

Hello and greetings from the Netherlands!

I am a microsoldering noob that just recently got into microsoldering and board repair, mainly as a hobby for now. I started hands-on practicing about a month ago by buying broken (mostly water damaged) iphone 6 phones. I've already managed to repair a few boards, which I think is pretty cool!

So now I'm working on this iphone 6 board which was severely water damaged. First thing I did was hook it up to bench power supply and immediately saw it was shorted as expected. I cleaned the board and verified short on main with my multi meter. I then knocked of the big ol' rusty cap next to wifi chip and that removed the short on vcc main. I replaced this cap with one from a donor board.

Next I proceeded randomly testing caps on the board and I found another short on PP5V7_SAGE_AVDDH. Since there are only three caps directly on this line I removed them one by one, checking for the short after each removal. With all caps removed from this line the short was still there. I proceeded by removing one of the ICs this line connects to (Meson). After removing this chip the short was gone. I reballed the chip and put it back. The short was back as well. I removed the chip again and replaced with a chip from a donor. Now the short was gone from this line! (I did put the caps back as well)

Going back to randomly checking caps on the board, I can't find any more shorts. I hook the power supply to battery connector, connect a screen and power it up. No smoke, good, aaand BAM backlight!.. image! But... All is not how it should be. I remember the boot screen to be white, and not pink! And the Apple logo has a shadow like band extending horizontally left and right to the edge of the screen. I tried another screen, same issue.

I turn the device back off. I take my multi meter and measure the voltage drop to ground on each pin of the display connector and compare them to a known good board from a previous repair. All pins check out. I do the same for the touch id connector and find an OL on pin 1 and 3. I guess this might be due to the filters on these lines, but I don't think this should give me a pink image and image artifacts.

What would be good way for me to continue troubleshooting the image problem?

[Jessa_the_Professa]

Replacing caps is something to be cautious of—I usually leave them off if it is one or two of many and their position is tight clearance. The chance that you damage something else is high compared to the minor contribution of a single cap to the board. however you do need at least two caps on the 5v7 lines.

Im surprised that a short to ground on your 5v7line was under meson. I don’t think I’ve ever seen that. It’s always due to water at chestnut. The most likely case is that you changing meson put enough heat on the board to disrupt corrosion under chestnut and that cleared the short.

if you have an image artifact now, change chestnut

[keypuncher]

Hi Jessa,

Great suggestion not putting caps back if there are many of them on a line. I guess it comes with experience knowing how many and which caps need to be a on a line for things to work. Are there guidelines I can follow?

I did as you suggested and replaced chestnut (with one from a donor). Unfortunately the problem persists, but it gets weirder. I tried again with another screen and this time the second screen gave me only backlight and no image. I tried with a third screen and that one didn't give me anything (no backlight, no image). I tried all three screens with my reference board and they all work fine. I tried each screens again and the different behaviors between screens seems consistently tied to which screen is connected.

I wonder if this could be be a connector issue. I do see some damage on the connector around pin 22 and its two adjacent pins. It also looks like pin 29 and 30 are very slightly recessed. What do you think? Is this a plausible cause?

[Jessa_the_Professa]

It’s not the connector, leave that alone. Remove meson. See if you have image.

[keypuncher]

No Meson, Yes Image! Why did removing meson give me image? I would have never thought of removing meson at this point. Is the meson chip itself faulty? Is it some interaction between meson and another component that caused an issue? So many questions...

[Jessa_the_Professa]

it is common for people to bridge the 5v7 line to something else under meson, especially with reballed chips. Sometimes the chip itself becomes internally bridged.

[keypuncher]

Ok, Thanks Jessa!