Client came in with no power to A1465 that worked fine yesterday - no liquid spills. Green / orange light ok on the magsafe.
No fanspin.
Check fuse F7140 -> blown. PPBUS_G3H ok from ISL side.
This means there was a short circuit event to blow the fuse. Removed battery / no power -> F7140, pin #2 (downstream side) to ground = 0.3 ohms (!!!).
Have the proper PPBUS_G3H voltage on F7140, pin #1 (producer side).
This means a damaged cap downstream (consumer side).
Used our SHORTKILLER (could have used a lab power supply) @ 0V7 (0.7 volts) -> applied onto pin # 2 (F7140; with red probe); black probe to metal ground. This tool is able to inject spikes of 30A.
Must keep the voltage for injection lower than the lowest - just in case CPU is shorting here to this rail.
Consumed ~7A and smelled a burn smell but unable to locate the fault. Forgot that we now own a thermal camera so dug it out (Qianli).
Hovered around the board with the camera during these pulses with the SHORTKILLER tool. Saw capacitor C7540 glow like a Christmas Tree. Repeated and found this cap glow like Rudolf's nose, again.
Plucked this defective cap but saw that the top side was cracked and lifted.
No more short circuit. Replaced the fuse from a donor. Board repaired.
No fanspin.
Check fuse F7140 -> blown. PPBUS_G3H ok from ISL side.
This means there was a short circuit event to blow the fuse. Removed battery / no power -> F7140, pin #2 (downstream side) to ground = 0.3 ohms (!!!).
Have the proper PPBUS_G3H voltage on F7140, pin #1 (producer side).
This means a damaged cap downstream (consumer side).
Used our SHORTKILLER (could have used a lab power supply) @ 0V7 (0.7 volts) -> applied onto pin # 2 (F7140; with red probe); black probe to metal ground. This tool is able to inject spikes of 30A.
Must keep the voltage for injection lower than the lowest - just in case CPU is shorting here to this rail.
Consumed ~7A and smelled a burn smell but unable to locate the fault. Forgot that we now own a thermal camera so dug it out (Qianli).
Hovered around the board with the camera during these pulses with the SHORTKILLER tool. Saw capacitor C7540 glow like a Christmas Tree. Repeated and found this cap glow like Rudolf's nose, again.
Plucked this defective cap but saw that the top side was cracked and lifted.
No more short circuit. Replaced the fuse from a donor. Board repaired.
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