Chosen Solution
Hello. I have a strange problem with an iPhone XS motherboard which I recently began working on. When the power supply is plugged into the motherboard, it immediately draws a ton of amps and gets EXTREMELY hot. I separated the motherboard, and narrowed it down to the U3300 chip. I put some rosin smoke on it, and noticed that there is only one pad of the chip which gets hot. I replaced the chip, and still, the short was there. The pad which gets hot is on the PP_BATT_VCC line, which tests fine with a multimeter. Does anyone know how to fix this issue? All the other capacitors look fine on the line. I have come across this same issue multiple times on some iPhone XR motherboards but I couldn’t figure out how to fix it. Thank you for your help Update: I think the board is shorted to ground by the one pad that overheats but i’m not sure how to fix it.
hello Colby, it is extremely important how many amperes it is and at what point you notice the short circuit. Start by making friends with your multimeter. It is really a friend of every microelectronics. If the short circuit appears immediately after turning on the voltage, you probably have a shorted PP_Bat line. You have to confirm it. If not, you’ll probably find it in a different baseline right after you try to run it (when you turn on the voltage). On the other hand, use a multimeter to check the pads under the Tigris IC that you suspect are short-circuited. Enter the measurement result here, I will try to help you interpret it. If it is actually PP_Bat the result will be close to 0.000 and you will look for the short elsewhere. It is also likely that you have a problem with a properly seated chip. It really takes training - it won’t come by itself :-) (get a time for it). If I’m right, the measurement in the PP_Bat line will be around 0.400 -regards and fingers crossing
The U3300 itself not shorting the capacitor on the line is shorting. Check it and find a faulty one.
