iPhone 6 No Power

[Computer Cave]

I have an iPhone 6 that came in from another repair shop. The backstory is that "as they were replacing a battery while tired and a screwdriver slipped while replacing the battery connector cover, there was a spark, and now only the CPU gets hot". The phone looked perfectly normal with visual inspection no red water indicators, no big gouges in the solder mask. I removed all the shields in hopes of seeing a nice burnt component that would be the trail marker for the journey. Sadly this board keeps it's secrets closely guarded. With the shields of I first checked to see if VCC Main was shorted at the battery connector, no luck. When I connect the phone to the DCPS, and prompt to boot I get a solid 0.036 Amp draw at 5V. I have a baseline draw of 0.006 for the DC Power Cable "Octopus-thing" Eventually after 2 mins or so the CPU will get warm but not burn your fingers hot. I get 0.89V on PP_CPU and 273 Ohm resistance to ground on that rail as well (0.192V DM)

I am unfortunately worried that the CPU got zapped and this board is long for this world but I am hoping that my assumption is just a novices flawed logic! Thank you all in advance!

[Sly]

Hi,
Have you ask the other shop where did the screwdriver slipped? If they can remember it might give you an idea of what line got zapped.
The battery connector of the iPhone 6 does not have much components around it. Mostly shields and some underfill components near the charging port connector. Seems like it would be difficult to short something there while the screwing in the battery connector shield...

[Sly]

Does iTune detects it?

[Computer Cave]

iTunes does not detect it, the previous shop says they were screwing in the battery connector cover and the screw driver slipped I was thinking it might have hit one of the "gas gauge" capacitors by the connector but nothing seems out of place.

[Sly]

Since you have low current consumption from your power supply, you most likely dont have a short.

So you might be looking for an open line. A guess as to where to look would be a filter that has blown along any of the lines of any components located near the battery connector.

You could Check those lines, compare them to known good iphone 6.

Do you that would make sense? It would be nice to know your thoughts.

by the way, 5V might be a bit high for you dcps. Battery charge is between 3.8 to 4.3V

[crea2k]

5v is waaay too high, it's possible you've blown something up with the testing as a charged lithium ion battery is 4.20v. Usually the battery overcharge bms kicks in around 4.25v so 5v is hell of a lot more.

the gas gauge lines won't stop a phone turning on, only booting stable / charge state reporting.

[Computer Cave]

Sly, the possibility of an open line does sound more probable I will check for filters or resistors that may be way out of spec. I can’t believe I didn’t even think about why I was using 5V on the DCPS. I was just autopiloting and putting it at the USB charger voltage. iPhones and Macs may share logic boards but mancare they totally different worlds! I’ll keep you guys posted with my findings

[Computer Cave]

I still haven't found anything of value by closely observing the board and following the VCC Main line. I did notice however that the phone is not prompted to boot from the dock flex being connected to a computer only by the power button in a chassis. Is it worth checking to see if the Tristar chip was shorted?

[Sly]

I would say so, but maybe someone else has an other idea?

maybe take some voltage mesurments with a known good battery and prompt to boot via usb. Before changing it, does it have power going to it?

[crea2k]

I change tristar and Tigris for fun lol, as they are the cause of many many dead phones. I'd change them out as a pair to rule them out as if it's not prompting to boot from the dock something isn't happy.

[Jessa_the_Professa]

Ack--5v on DCPS? Never do that again!

If this phone was in front of me my thinking would be like this:
1--Do I see anything that looks burned? No---so screwdriver slip/spark is fake news.
2--Phone was working, then not working at a screen change---consider long screw damage somewhere
3--Phone was working, then not working with no physical damage---consider tristar fault.

I would not have taken the shields off on this phone in the absence of any water damage---that by itself is a variable, look very very closely for any signs of shield removal damage. I've seen phones dead after shield removal with a hairline crack at r0303, and with nudged vibrator driver, and of course CPU overheated from blowing hot air at edge of shield instead of top side of shield (never aim air at the edge of board sideways).

Your DC supply results sound unusual. I would repeat that test, using normal battery voltage only, and if you can't get a the phone to prompt to boot from usb---that's your biggest lead to follow. Why not? Troubleshoot that.

[Computer Cave]

I have replaced the Tristar and Tigris as a pair, the Tristar chip was getting 1.79V before replacing. Still will not boot from USB or even prompt the DCPS shows 0.006A baseline for my DCPS. When turned on with the power button there is a a constant 0.385A. When using a USB ammeter 0.01A draw. Even when outside of the chassis and 3.8V on the DCPS, and USB to PC the CPU gets hot without an increase in amp draw.

[Jessa_the_Professa]

I said before that your DC power supply test sounds unusual---which it sounds like you've cleared up by clarifying a typo, but let's be sure.

Earlier you said that your phone would prompt to boot with 0.03A steady current draw--a very low reading that doesn't really make any sense
Now you are saying it draws 0.385A which is a high reading that is clearly a short circuit.

So now you know you have a short circuit---that's a great problem to have.
You have no usb detection, despite changing tristar and tigris. There is very little required for a phone to make a connection to usb--so follow that lead.

You looked for 1v8SDRAM as one of the tristar inputs and it is present. Why not also look for 3v0 tristar? Some line on this phone is short to ground---probe around, see if you can find it. Signature problems says to rule out NAND power line shorts.