Chosen Solution
Hi all!! I have an iPhone 6 that took a bath in the toilet. Before it turns forever into a “$@$*!&” phone, I started to repair it but now I have few problems that maybe some good users can give some help. Here are the steps I did so far: 1 - I have disassembled the main board and took all the EMI shields out. The damage is clear and I could see a lot of corrosion marks in some main capacitors. 2 - I started cleaning the hole board with a good and proper solution and everything looks fine now. 3 - Then I have tested the VCC_MAIN and it was short. I tested with a good power supply with the current limit set to 1.5amps and it was obviously short because the power supply reaches immediately the limited current. 4 - I took a look on the VCC_MAIN line and I found some dead and short capacitors which I have removed already. Q1 - Now I have no short anymore but the VCC_MAIN resistance is between 20 and 30 ohm. Is this a normal value? Before it was 0 ohm = short. 5 - after that I tried to power the board again and the current dropped to 0.6amps, which obviously means that there’s still a problem elsewhere. 6 - I have found that the U1501 was heating (no other IC was getting hot) by dropping some flux over it, even with those 0.6amps. 7 - then I have followed all the capacitors in the power lines supplied by that IC and I have found some more shorts which I have also removed, but still I am having a short somewhere and I dont know where. Q2 - should I remove the IC U1501 and test the VCC lines before I end with no caps? Q3 - After removing that IC the VCC_MAIN should give a higher resistance value? What would the next steps? Thank you very much and if you could help me I would really appreciate.
VCC_MAIN at 20-30 Ohms is too low. You should be reading approx. 0.350V in Diode Mode. You still have a partial short that you will need to find. Even if one cap on a line is short, they will all look short. Finding a VCC_MAIN short can be a pian in the you know what. It may be another cap but if U1501 was in bad shape, I would remove it to see if that removes the short. Otherwise, You will have to remove stuff one by one until you find it.
