Water Damaged not booting tried lots looping with 70mA draw
Hi I have a water damaged iPhone 6 that has come to me for repair. There was been a previous repair on it but I do not know if it is related. C5202_RF has been replaced and although electrically sound is very messy.
Taking of the shields all is clean except for the speaker IC which is heavily corroded. I have removed this IC and replaced the bad and shorted CAPs around it. It was all on the PP_BAT line....
With bench PSU connected it draws current without being prompted to boot. I then removed the VIB motor IC and now no current draw until prompted to boot. When promoted it draws around 70mA for a few seconds and then goes back to 0mA and continually loops. I have noticed during this cycle that the major lines from the PMIC are all OK but nothing out of the BASEBAND power chip - perhaps too early for that in the boot cycle. VC_MAIN is good at 4v but it does drop to around 3.8v shortly after power up and I am wondering if something is bringing the line down or not causing it to restart continually.
I have replaced Tristar, Tigris and the PM IC (as they all use PP_BATT and that took a big hit) and also the BASEBAND PM IC. Also ultra sonically cleaned PCB - no other visible damage.
Still no difference in the looping every few seconds of 70-80mA
Any ideas? have spent a lot of hours on this one replacing a good 10 components and made some progress.... currently Speaker and VIBE IC's and C5202_RF are all removed everything else in place.....
Help much appreciated and hope this will lead to a good reference for others with this fault.
I have not had any responses :-( but I have still been looking for answers so this may help someone with a similar problem. If anyone out there can help or add to my problem I would still be grateful to learn.
70mA according to Jason and Jessa has pointed towards I2C signalling problems. I2C is a standards based signalling protocol explain HERE Basically for each I2C communication line there are a a pair of lines, a clock and data line, and they operate more or less at 1V8. There are three main I2C lines in the iphone 6 and I have tested all of them and they are fine. Here is an extract from the schematic showing the addresses of each Chip on each line, for my problem I think it would have revolved around I2C0 or I2C1 where Tigris / Tristar / PMU live. Common problems are the pull up resistors on this lines or I guess being grounded. As I say for me they are all good.
My problem is still that I get 70mA after prompt to boot and this resets itself after a few seconds and continues on it merry cycle. All PMIC voltages look good when VCC_MAIN is up.
I only had a Tigris from a donor board - I have some more coming in and will try a brand new Tigris when I get them and update again.... I also suspect something may be bringing down VCC_MAIN at boot time
but this may be very hard to find.....thanks for reading / contributing.
Cette question est-elle utile ?