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Hi, hoping you can help with a weird problem. I have a 128 Gb iPhone 6 which doesn't boot or charge, and isn't seen by iTunes. I changed Tristar (no change) and then Tigris but nothing. When connected to DCPS the phone draws 15mA before prompt to boot, and when prompted to boot goes to about 110mA and then stops there. I checked the voltages around Tristar and all are fine. I checked the voltages around Tigris and most are good (VCC_MAIN, BATT_VCC, PMID_CAP and PP5V0_USB) and these are all good, however I'm getting a very low reading on the CHARGER_LDO line which connects to pin G4 under Tigris (should be 4.5v but is less than 1v). There are just 2 caps on this line (C1403 & C1410) so I removed them just in case one was partially shorted but no change. I took Tigris off and the short disappeared (but the phone wouldn't boot) but when I put 2 different Tigris on the short re-appears. This is weird, because according to both Phoneboard and the schematic there isn't anything else on this line at all? This line doesn't connect to PMIC or CPU or anything else that I can see, and I've removed the only 2 components on it but as soon as I re-install a Tigris I get this low voltage on the line. Do you have any idea what can possibly be causing this? Is it damage to the underlying layers of the board, and if so is there anything I can do to get round it or - as there's nothing on the line - could I just remove that pin on the Tigris IC? Grateful for any suggestions you can make on this.
Well, you have to understand that ICs, like Tigris, are circuits that contain diodes, transistors and other components, so if that line is shorting after you replacing Tigris, then maybe it's not that line that is bad in the first place? You'll have to look at the schematics to see what else that line connects to. Work your way backwards.