Chosen Solution
Hi, I have an iPhone 6 board which seems to have all the PP_LDO lines missing (all of them). They are not shorted, as the resistance to ground reads in megaohms, but when the board is powered on (screen shows restore with iPhone) the lines are absent. I want to ask if this is normal when the phone is in the DFU mode? More or less everything is disconnected from the logic board. Unfortunately I do not have a known good board to check that.
Those lines should be active when you power up the logic board. Have you also checked the VREG_SMPS1 (2/3/4) lines to see if they are generating any output voltages? I would start by confirming that VBATT_S1 (2/3/4) are present and not shorted (they shouldn’t be because they are directly connected to VCC_MAIN). If none or most of the outputs voltages are present, then I would suspect the PMICRF first. Be careful when you replace it because there is a trailer park’s worth of caps right next to it and when they start shifting around, they tend to bridge easily and it’s hard to separate them.
