Chosen Solution
A wet 5S came in and I washed the board in an ultrasonic cleaner. All it does now is flash the Apple logo and draw a steady 0.2A for a few seconds and then shuts off. Is there something in particular that I should be looking for (the board is visually fine) or do I really need to start testing components? Any help would be greatly appreciated and thanks in advance.
Realistically, if this phone was water damaged, you’d be lucky if a modular component would solve the issue. You still need to try though but once it’s clear it’s not a modular issue, then you’ll need to start probing the board. If you suspect a logic board issue, check PP_BATT_VCC, PP_VCC_MAIN and PP5V0_USB. I would start by checking to see if those rails are shorted to ground. If one of these rails is shorted to ground, then you will need to identify what is causing the short. It could be a bad decoupling capacitor, conductive debris or defective IC that is directly supplied by those rails. Then you move onto the PMIC and check the voltage rails it generates: The PMIC generates ~15 voltage rails. They are all important (for obvious reasons) but the ones to check first are as follows: PP_CPU, PP_GPU, PP1V8_SDRAM, PP1V2_SDRAM, PP_VAR_SOC, PP0V95_FIXED_SOC, PP3V0_Tristar, PP3V0_NAND, PP1V8_ALWAYS and PP1V0. The PMIC also generates, what I would consider secondary, yet still important voltage rails for the following sub-systems: PP3V0_MESA, PP1V8_VA_L19_L67, PP3V0_PROX_ALS, PP3V0_PROX_IRLED, PP3V0_IMU, PP3V3_USB and PP3V3_ACC
Start testing with / without components for example, boot with: Front camera unpluggedReplacement battery, try another charging port plug in temporarilyBoot with DC Bench power supply with appropriate iPhone battery connector adaptor for power supply.
