A1706 Can not Boot when Press Power Button with Abnormal Standby Current

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A1706 Can not Boot when Press Power Button

Motherboard No. : 820-00239-A

Malfunction : Can not Boot when Press Power Button with Abnormal Standby Current

Troubleshooting:

Remove the back cover, disconnect the battery and measure the current to see if the current changed.

1.If the current is not change, it means the problem is from the standby circuit.

2. If the current is change, it means the problem is the from the battery, as we know, if we do not charge the battery for a long time, the voltage of the battery will be very low, and the battery voltage over-low protection system will be active.

In this situation, we can change another battery.

We disconnected the battery and check the standby current again.it was still abnormal.

For new type-c circuit, there is a detective circuit for adapter, we can check the whole  power supply steps, the voltage should be from 5V to 20V. Because the standby current was abnormal, so we should check if the PBUS was generated. We opened the schematic and bitmap, found out the Page PBUS Supply and Battery Charger circuit. 

A1706 2016 can not boot up

On the first page, we could find out this circuit is in page 66.

A1706 2

Step1. We checked the diode value and voltage on charging inductor L7030, normal diode value should be around 305, voltage value should be around 13.1V.

Step2. We checked the diode value and voltage value on both sides of Fuse F7000, the normal diode value should be around 423, normal voltage value should be around 13.1V. The voltage on the right side of F7000 is PPBUS_G3H.

The diode value on L7030 and F7000 was normal after we checked, but the voltage value was 0, which was abnormal.The Public Power (PPBUS_G3H)wasn’t generated, so the standby current was abnormal. The PPBUS_G3H was generated by charging IC. Then we continued to check the charging IC.

A1706 3

Charging IC is ISL9239, when we plugged in the charging adaptor, the voltage on PPDCIN_G3H was 5V, the working conditions of the charging IC are as follows:

Main power P_IN:  5V,

VDDA: 5V,

VDDP: 5V,

EN_VR1:3.3V.

All the values were normal after we checked, the enable signal PM_EN_P3V3_G3H was generated from pin EN_VR1 of charging IC, and then transfered to U6903, then U6903 works, and generated PP3V3G3H_LX, and then transfer to L6900 to generate the PP3V3_G3H.

A1706 4

A1706 5

We checked the output voltage of L6900, it was normal value 3.3V , PP3V3_G3H supply power for SMC(U5000). When the input power was 5V, Type_c control IC (U3200)comunicate with SMC via I2C_UPC_X_SDA2I2C_UPC_X_SCL2, and out put the signal USBC_XB_CC1USBC_XB_CC2 to the power connector J3300, to boost PP20V_USBC_XB_VBUS the 5V to 20V.

When we checked the fuse of F3001, the voltage was 20V, it means the working process bettwen Type_C IC and power adapter was normal.

A1706 6

A1706 7

The mosfet Q3200 was controlled by Type_C control IC U3200, when the voltage raise from 5V to 20V, the mosfet was conducted. The PPDCIN_G3H line was devided into two rails, one is to the P_IN of charging IC U7000 via current detective resistor R7020, the other rail is to AUX_DET of charging IC via R7015. We checked the voltage on the two pins, voltage on P_IN was 20V, voltage on AUX_DET was 5V, both were normal.

A1706 8

A1706 9

Then we continued to check the voltage of AUX_OK on SMC_AUX_OK, the value was 3.3V, which was also normal, it means the input detective signal of adaptor was normal.

A1706 10

 

After we checked all the voltage above, it means all the working conditions of charging IC U7000 were normal, the diode value of charging inductor L7030 and fuse F7000 were normal, but the PPBUS_G3H still could not be generated, it means the charging IC was broken.

A1706 11

macbook A1706 boot up issue

We replaced a new charging IC U7000 and checked the PPBUS_G3H on fuse F7000 again, the value was 13V, it’s back to normal. We assembled all the parts, turned on the macbook and tested, everything back to normal, problem was fixed.

Summery: 

The PPBUS_G3H wasn’t generated because of the charging IC was broken, and then the macbook cound not be trun on.

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