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[Sticky] iPhone XR Heavy Liquid Damage, Reboot, Hang, Shutoff  

 

iTesla
(@idea)
Archetect Admin
Joined: 8 years ago
Posts: 10342
Topic starter  

Have received this heavy liquid damaged device and decided to repair because customer need data, the device was rebooting, hanging and shutting off.

Took off the CPU and PMU shields with low melt alloy, but bottom ones used dental burs attached to my dental dremel to scratch the welds in those specific area (must be careful to not go through and cut something) and then low melt solder added with a thin soldering copper tip.

Have looked inside and found this.

What i decided to do first is:

  1. clean soft glue around connectors (found additional poop)
  2. resolder corroded connectors legs
  3. resolder all corroded components (using acid based flux which does a great job, not recommended around IC's without glue, better used where IC's are glued)
  4. replace corroded capacitors and resistors, some resistors had wrong values higher or lower!
  5. clean the LB after rework in thinner

After this steps decided to test the LB and to my surprise it was dead, no DFU no detected at PC, the reaction at DCPS was 0.040/0.050ma was playing like that and by this i have understand the PMU or CPU does not get initiated, i was partially correct, my 6th sense was telling "hey this is related to CPU Quartz you have touched it with soldering iron at 400C of temp" but i did not pay attention, so this what i did.

  1. tested AP voltages all of them and they were all important generated meaning PMU was fine also because he is protected very good with glue and it can be excluded.
  2. tested all connectors readings (except Debug one) and found many wrong readings related to strobe, Cam PMU voltages, LCD voltages,MIC's but also found 2 LCD MIPI traces were short at the 4 leg filter, did a resold and was back to normal.
  3. have reballed this IC's which had corrosion around them: Yangtze Charger re-balled/replaced, Chestnut, Cam PMU, Rigel Driver, Bottom Speaker Driver, Taptic Engine Driver, BB PMU re-balled/replaced, both Strobe Drivers, LAT IC and CPL_K

After each IC work i was testing but no change, i observed that after i try power on the device consumption was showing that it tries to initialize to power but very hard after some seconds it show the 0.040/0.050ma playing, so again into my head appears the other person which we call "intuition" and says "fuck you it's the CPU Quartz you have touched it with soldering iron a couple of times during re-soldering process" well this time i have listened to my "intuition" and took the Multimeter and tested the 2 positive traces and to my happiness one of them was short to GND, even after i unsoldered the quartz it was still short on one trace, so i took the CPU Quartz from iPhone 6 (the replacement on XR LB was done using soldering iron, no heat gun!) because i know apple never changed it's frequency for CPU even on old models and voila the phone booted until swipe up to unlock, have ordered the other parts and will test further the other functions and let you know, but also will take photos after i reworked on the LB.

It's not excluded there were allot more faults and i have solved them because the device falls to 0.000 in standby as it should.

I hope this story will show you how much of persistence is needed into this type of repairs, and from what i remember i have touched many Quartz in the past but never had them short in this way maybe this one was weak after liquid damage, who knows, nothing is excluded.

P.s. i don't regret reballing those IC's there were poop under them and the readings came back to normal at connectors after reball, only Audio Codec remains but i hope it will not be required to reball him.

Will keep you updated!

Do not wait that i feed you with the tea spoon, the site is full of info, have patience to search and read other peoples topics, because this is a great way to learn from others.


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iTesla
(@idea)
Archetect Admin
Joined: 8 years ago
Posts: 10342
Topic starter  

Have received all new parts, battery, LCD and housing, everything assembled and was preparing to Restore, it was connected at PC and suddenly the image disappeared like losing power or contact, took off tested at DCPS looking like it was booting but no image, did some tests and decided to replace the Chestnut IC that powers the LCD, took it from iPhone 6 cause of same part number and preparing to test if image solved, pressing power button seen like begin to power on but no image at some point FUCK and it got shorted and heating, after testing found out VDD MAIN got around 0.760 readings. Then i think to myself WTF i tested this board a couple of times and all was fine now after new parts it's dead and yes most importantly the PMU got shorted and heating, then i decided and tested the Chestnut coil and found out it had around 60OHM which is very bad, the good coil have 0.05OHM tested on other LB and replaced it from that good LB but too late the PMU already is fried.

Now after all this i don't know WTF happened, i never had before such weird stuff, but i think that it is very possible the PMU was barely breathing after such heavy liquid damage and after longer time being on he just gave up and the Chestnut Coil was out, there seems some connection but i can't get it, the Coil is connecting with VDD MAIN and the Chestnut was still good so not sure how it went to short the PMU entirely.

I decided to replace PMU but can't buy new one the Aliexpress after COVID have only expensive shipment to me, so i think to harvest the PMU from iCloud LB possible will do some vids, hope everything goes well, will update if something pops up.

Do not wait that i feed you with the tea spoon, the site is full of info, have patience to search and read other peoples topics, because this is a great way to learn from others.


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