Re: A1708 820-00840 no power
My bad...thank you for the correction. Too many netnames in my fading head.
Remove all power. Measure the resistance to ground @ F7000 (pad # 1).
This should be with F7000 fuse removed.
Next, measure the VOLTAGE to ground for:
SMB_SMC_CHGR_SDA
SMB_SMC_CHGR_SCL
the above SMBUS (I2C) lines are used to communicate with the ISL9239 @ U7000 to allow for this IC to become either a BOOST or BUCK regulator.
Since you have 20V as input, this regulator should enter BUCK mode (high input voltage; low output voltage).
My bad...thank you for the correction. Too many netnames in my fading head.
Remove all power. Measure the resistance to ground @ F7000 (pad # 1).
This should be with F7000 fuse removed.
Next, measure the VOLTAGE to ground for:
SMB_SMC_CHGR_SDA
SMB_SMC_CHGR_SCL
the above SMBUS (I2C) lines are used to communicate with the ISL9239 @ U7000 to allow for this IC to become either a BOOST or BUCK regulator.
Since you have 20V as input, this regulator should enter BUCK mode (high input voltage; low output voltage).
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