Released on September 19, 2014, this 4.7" screen iPhone is the smaller version of the iPhone 6 Plus.

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iPhone 6 power consumption fluctuating and not powering up

I have a customer who brought me an iphone 6 with a story that it was working fine until a 2' fall from his computer tower which resulted in it not powering back on. first thing I tried was a couple hard resets (No Change). I put my USB Detector on to see if it was taking power and it is taking .51 and then jumping to 0 in a couple seconds then back to .51, then 0, then .51, .39, .14, 0 and back to .51. (Repeats indefinitely)... Some sort of power loop? Anyway, I tried a different Charging port and battery with same result. Confused by it, I tried a new U2 and still no change. There doesn't appear to be a short on VCC and I am stumped... Any suggestions on what to check? I'm not sure if PMIC would be the guilty one or not and thought I'd post to a few experienced techs to see if anyone else has had this issue. I asked him if there was previous water damage and he assures me there wasnt, but the water mark tape by Sim tray is red and missing from the other spot on board. No visible damage or corrosion. Any tips would help...

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Chosen Solution

Does iTunes recognize the phone? If it does, then it would indicate that Tristar is probably okay. Remember that Tristar is above all else a communications chip. TIGRIS is responsible for charging.

I would start at the beginning and check the main rails (which you probably did already). Then I would move onto the rails that the PMIC produces. Look to see if there are any shorts (careful, PP_CPU & PP_GPU are low resistance, they may "beep" but that doesn't mean they are shorted) or low/missing voltages. That could help point you in the right direction.

You could try the shotgun approach and indiscriminately replace IC but Changed U2 chip and phone displayed dead charging symbol then stopped. in that. Sometimes you don't have a choice but I like to understand what's going on first.

So start probing and get back to me by commenting on this answer.

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Nice bench by the way ;>)

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Thank you :) And Thank you for your reply... No, Itunes does not see it. I have replaced Tristar with 2 new IC's but still same results. No shorts on the main rails but Batt VCC still shows the fluxuating in voltages... they measure correct around Tigress and Tristar for a split second and then start the fluxuation. I haven't replaced Tigress yet.... new IC's come in today

I haven't learned the process of measuring the rails around PMIC yet, but going to search for tutorials on how to do it. I have ZXW, so shouldn't take too long to learn.

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Put your black probe on a ground point and then use the red probe to measure the voltages. For example, use ZXW to look for C1243 to measure P1V8_SDRAM.

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Okay, I figured out the different rails to test and found similar issue happening on all test points. CPU, GPU, and others... Voltage shows good for a second and then drops to 0 repeatedly on all rails.

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I ordered a new PMIC believing good voltage on VCC Main (Incoming) but outgoing voltage from PMIC is fluctuating. If it was only on one rail, I wouldn't believe it was PMIC, but since it is all rails, am I right to believe there's a good chance that PMIC is the guilty component?

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