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A1707 820-00928 erratic 5V+bootloop on USB-C

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vinaypundith

New member
Got an 820-00928-A (no liquid damage, but a crude battery replacement some time ago, was working until now). Doesn't charge - USB-C port stays at 5V 0.2-0.3A, and bootloops every few seconds. BUT - if I leave all power from the board disconnected for some time (like 15 minutes) then plug in the USB-C port, it will go up to 20V, 1 amp, and the screen lights up and shows a low battery icon. Still can't boot up the laptop, because it stays at 5V if I connect the battery, and with no battery it just shows the low battery icon.

PP3V3_G3H is at 3.38V, DCIN_G3H at 5.08V. I'm not sure what else to test.
All 4 ports behave the same - 5V, 0.3A, bootlooping.

Any help would be much appreciated!
 
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vinaypundith

New member
the resistance is much higher on a working board, i presume that short is my issue then. do you have any suggestions how to trace the short in that circuit?
 
2informaticos

2informaticos

Administrator
Staff member
How can be much higher on working board???
As per schematic, 2 ohm (+5/10 miliohm); multimeters show 3-4 ohm normally.
 
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vinaypundith

New member
My mistake. I did something wrong while measuring the other board. The resistance is about the same. What else should I check?
 
2informaticos

2informaticos

Administrator
Staff member
If battery is dead, or not connected, A1707 doesn't start with 61W charger in normal mode; only in SMC bypass!!!
 
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vinaypundith

New member
I changed the battery for another used one, and the laptop started working fine. The little screw on the battery BMS PCB that the motherboard's terminal mounts to was stripped. The battery had worked with my other A1707 motherboard, but not with this one - not sure why. Anyways, thanks for your help!
 
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