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Released on September 19, 2014, this 4.7" screen iPhone is the smaller version of the iPhone 6 Plus. Identifiable by the model numbers A1549, A1586, and A1589.

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No boot - problem with Charger_LDO?

Hi, hoping someone can help with a weird problem (Minho??). 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 going up and down in value but never beyond this value.

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 each time. 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. Does anyone 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 on this.

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1 Answer

Most Helpful Answer

IIRC, Charge_LDO is at 0V when on battery power only and ~VCC_MAIN when charging

I think your issue is elsewhere and you need to take a step back and probe your board without making any assumptions. Tristar/Tigris is a common repair but sometimes we get blinded by that and forget to look at the rest.

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Minho is right on that LDO regulator. What is the phones history?

You should be getting 0V before prompt to boot.


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