Chosen Solution
Hello All i Have an iPhone 7 that No Power Up I testet its Logic board for any short but it has no Short I test all the voltages they was ok when I connect it to charger its draw 0.41 miliAmp but its not detected by computer, SO the problem isn’t the NAND! i try to use DC power,when i press the PWR Button it draw 0.06, 0.8, 0.11 and repeat this circle….,No image, No heat… can anyone help pleasse?and sorry for my bad english.
Hi I have seen this a few times. If the DCPS is going back to 0.00 then it sounds as if one of the RESET lines is being triggered. These are IC’s that can cause a reset to the main PMU e.g. TRISTAR_TO_PMU_HOST_RESET. It could be many things but I have seen this caused by TRISTAR, failing that it may need a CPU reball. Has it had a drop or anything? I would also double check for shorts on the NAND power.
I have a phone which was run over, but the board looks to good condition. No obvious bend in it. I trigger the device to boot via the dock and hooking up a USB cableThe device shows some current being drawn and the pattern repeats, between each pull it drops to 0A. The approximate values are 0.8A, 0.6A, 0.3A, 0.2A, 0.1AAdditionally, the USB meter shows 0.00A throughout. On a rare occasion it goes to 0.40A and then 0A I started to learn the various power lines on the board and checked a few. VDD_MAIN pulls approximately what the DCPS suppliers i.e. 4.1VVDD_BOOST appears ok as well without any short.The above power lines, per my understanding are pre the PMIC. On this output side, it supplies the NAND, SDRAM, CPU/GPU (SOC) with 1.8V.When checking the voltages, I don’t see anything on the CPU/SOC/GPU. They are all 0.0V (PP_CPU_VAR, PP1V1_SDRAM, PP0V9_SOC_FIXED), but I do see a small voltage spike on the NAND line PP3V0_NAND. It seems to be relative to the current my DCPS pulls. The most I see is 0.08V, much lower than the expected 0.85V??? Can this be caused by a bad Tristar? Looks like a reset line may be pulled between each current draw.
