issue after touch ic replacement. &quot;curtains&quot;

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issue after touch ic replacement. "curtains"

ive done numerous touch ic repairs but this is the 1st time im seeing this. yes, i ran the jumper to m1 then insulated it with uv solder mask, and used coins as heat sinks as to not reflow surrounding components. my issue is lines on the screen and cant see apple logo. 1st i tried reballing the meson ic from the phone. when i got the lines i assumed a bad chip and used a new one. still same issue. any ideas what i can check? i already went down the lcd fpc in diode mode with multimeter and compared to known good board. everything seems right. then i pulled meson and turned on the phone still doing the same thing with the chip removed. just looking for ideas as to what i can try next.

Edit: I got it working, turns out it was a strand of the tape that covers the touch ic area partially shorting one of the resistors (r2434/r2435)

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lukerockhill @mobilemedic

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never have i been so stumped but i finally found out what the issue was! it was a tiny strand of the tape that covers the touch ic area touching r2434 and r2435. never seen that before, stupid strand had me pulling my hair out for hours....

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Thanks for the update!

5 de oct. de 2017 - de Joseph Hughes

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score 1 · Answer 1 · 2017-10-04T12:30:40-07:00

Minho @refectio

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You might want to check Chestnut and the surrounding circuitry on the flip side of the board. It does supply both the LCD and the Touch circuit. Despite your precautions, you may have caused some reflowing on the other side.

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i look under chestnut with microscope the balls looks fine, and i dont wanna remove it unless im absolutely sure thats the problem due to its close proximity to the cpu

well i replaced chestnut and nothing changed. i dont think i got the board too hot because the tape around the fpc connectors isnt melted or deformed in the slightest.

That's unfortunate. I would have probed around before changing it though. Have you checked all the voltage rails?

4 de oct. de 2017 - de Minho

both 1v8 and 5v7 lines are present.

i just picked out all the underfill from the components around the fpc connector to see if maby one of the caps or filters lifted off the pads from the heat on the other side, and they are all securely in their place.

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Kevin Lee @hotshot_repair Rep: 13 2 · Answer 2 · 2018-03-19T09:54:12-07:00

I wanted to chime in and say I had this exact problem. It was a dark looking thread bridging C1577 to R2434. I didn't even notice it until I had tried 2 chips, and then found this answer, in a fit of desperation. My problem was almost the exact same. I would get half screen zebra lines, on the original screen, and my aftermarket screens would backlight but no image.

If I removed Meson, the original screen would still have half screen zebra lines, but the after market screens would seem to look ok, no zebra lines, and the screen looked good, albeit without touch.

I found this thread, and removed it and cleaned the board, and I kept Meson off, and retested. The original screen now works without zebra lines. I am moving on to reballing and replacing the Meson chip. I will edit this if I run into any further problems.

joel rakich @ripper Rep: 257 4 1 · Answer 3 · 2017-10-04T16:35:40-07:00

joel rakich @ripper

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I dont like to assume anything so i have to ask, did you try another lcd? I didn't see if you mentioned whether you did or not. Also Im curious what temp do you use to remove the touch ic's. Ive been starting with 270 to get them off then 240 from there on out. Never had an issue with anything else getting damaged and I dont use tape or heatsinks to protect the other chips.

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yes i tried another known good lcd as well as tested the lcd that was on it on another 6 plus. the screen is working. as for temps, im usually right around 360c. and i have done 10+ touch ic's this is the 1st one giving me problems.

does the nonleaded solder even melt at 270c? lmfao you must sit there for a good minute with heat on it.

I would say takes about a full minute to melt the original solder at 270. Once I replace the chip or solder 240 works fine. Most lead free solder melts around 220. The leaded stuff I replace it with melts about 170.

5 de oct. de 2017 - de joel rakich