Chosen Solution
Hi, Ive got an iPhone 6s with previous water damage. Ive removed all the shields and carried out a full clean inc Ultra sonic. Ive tested VCC_Main , BATT_VCC & PP_5V0_USB with the board unpowered and powered no obvious shorts or low resistance readings. Ive tested The Various PMIC output Rails PP_GPU, PP_CPU, PP_SOC, PP_3V0_MESA etc all seem ok. When i connect the logic board to DCPS with voltage set to 4.2v the logic board doesn’t draw any amps until i short pin 2 on the connector, the board then seems to boot normally with a steady increase in amp draw for about 3 seconds then the amp draw becomes erratic jumping from as low as .003a to as high as 1.03a it then fluctuates between these values. With a screen connected i get no image & no backlight. Any ideas??
You say you checked “the various” PMIC outputs. Did you check them all or only a few of them. That does make a difference from a troubleshooting perspective. If you have and they all checked out okay, then I would check the outputs from U_PMU_RF as well. Problems with the BB PMU can also cause bootup issues. If everything looks okay, I focus on the charging circuit and make sure it functions properly and then replace Tristar to see if that helps. Report back!
