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Released September 25, 2015. Model A1688/A1633. Repair of this device is similar to previous generations, requiring screwdrivers and prying tools. Available as GSM or CDMA / 16, 32, 64, or 128 GB / Silver, Gold, Space Gray, or Rose Gold options.

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iPhone 6s Water Damage


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??

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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!

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Minho thanks for your reply,

I checked the following PMIC outputs & got the following readings;

PP_1V1_SDRAM - 1.1v PP_3V3_USB - 3.2v PP_3V0_TRISTAR - 3v

PP_1V8_SDRAM - 1.8v PP_1V8_VA - 1.8v PP_0V8_Owl - 0.8v

PP_3V0_NAND - 3v PP_3V0_Prox_Als - 3v PP_0V9_NAND - .9v

PP_3V0_Prox - 3v PP_1V8_Always - 1.8v PP_3V0_MESA - 3v

PP_1V2 - 1.2v PP_1V8_MESA - 1.8v PP_Fixed - 0.9v

PP_CPU_SRAM - 0.8v PP_SOC - 0.8v PP_CPU -0.9v

PP_VCC_MAIN - 4.4v

I found a couple of rails that were showing no voltage, i assumed this was perhaps because the phone wasn't booting up.?





I will have a look at the outputs from U_BB_RF when i get a chance after work tomorrow.... i refuse to be beaten by an iPhone!!

Many thanks.


Certain iPhones will beat you, unfortunately.

PP_GPU only activates when the display is required. So you need to either push a power button or connect the dock to a charger or iTunes. That activates the display and then you can measure PP_GPU.

PP3V3_ACC is on for only a fraction of a second and isn't required or necessary to a properly booting phone. You'll want to follow up on PP_1V8_LDO8 though as it feeds the BB.


Evening Minho Thanks for the info,

Ive Managed to check the outputs from U_PMU_RF and all the readings are 0v. It seems like the BB & BB PMU or not receiving power. No lines appear to be shorted and resistance readings around BB are around 90ohms. Ive replaced BB_PMU with a known good and still no voltage on the output side. Im getting Vcc Main & Vcc Batt voltage at the switches before BB_PMU. Could this be CPU related? When Connected to the DCPS and booted it now pulls a constant 0.06a.

Any ideas?

Many thanks


So all of the U_PMU_RF outputs are at 0V and none of them are shorted to ground? Can you compare diode measurements of these outputs to known-good?

Assuming everything looks okay, I would check out the reset signals on U_PMU_RF such as AP_TO_BBPMU_RADIO_ON_L, PMU_TO_BBPMU_RESET_L and PS_HOLD_PMIC. Also check the reset output from U_PMU_RF (PMIC_RESOUT_L) to see if it corresponds to the inputs or the state of the IC.


Yeah they all measured 0v. I'll comprise some diode measurements from a known good board and then compare and see if anything obvious shows up. If not i'll check the reset signals as you've suggested and report back!

Cheers buddy.


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