This is a case study on a 'sudden death' A2141 unit brought in for service.
USB-C meter is @ 5v with ~0A current draw.
a) Disconnected battery. No power to the machine. Applied the Qianli Tail tester with the USB-C connector. Each USB-C power connector was green with the diode mode of testing. CD321x are not defective as originally thought.
b) PPBUS_g3h is not shorted but is a low voltage due to the low INPUT voltage of 5v being boosted. On a random power up attempt, PPBUS_g3h was at the expected 12v63 range AND input voltage was observed to be @ 20v for a few seconds. Power cycling between the 5v / 20v for a few seconds.
c) Upon probing assorted board voltages, observed that the PP2V5_NAND_SSD0 @ L9580 = 0v. Is the enable pin at the correct voltage for this TPS62180 (U9580) regulator?
Monitored the (too) tiny 0201 SMD resistor @ R9598 for SSD0_VR_P2V5_EN signal. This signal resistor is @ 1v8 on each side of the (too) tiny resistor. So the logic board is wanting to turn ON.
d) Next, is the painful removal of the logic board process. Once the board was dismantled from the (abused) enclosure - observed the regulator for this SSD as follows:
The SSD0 power rail has a normal resistance of ~57R ohms to ground. For this reason, still worth the effort to replace this common point of failure regulator from TI. Part can be sourced from Digikey / Mouser / Aliexpress (suggest in this order). Our DK package is lost in transit but expect it to arrive tomorrow(?). Will update this thread after the surgery.
SSD1 power rail is fine and stable @ 2v5 to ground. Also with ~57R ohms to ground.
USB-C meter is @ 5v with ~0A current draw.
a) Disconnected battery. No power to the machine. Applied the Qianli Tail tester with the USB-C connector. Each USB-C power connector was green with the diode mode of testing. CD321x are not defective as originally thought.
b) PPBUS_g3h is not shorted but is a low voltage due to the low INPUT voltage of 5v being boosted. On a random power up attempt, PPBUS_g3h was at the expected 12v63 range AND input voltage was observed to be @ 20v for a few seconds. Power cycling between the 5v / 20v for a few seconds.
c) Upon probing assorted board voltages, observed that the PP2V5_NAND_SSD0 @ L9580 = 0v. Is the enable pin at the correct voltage for this TPS62180 (U9580) regulator?
Monitored the (too) tiny 0201 SMD resistor @ R9598 for SSD0_VR_P2V5_EN signal. This signal resistor is @ 1v8 on each side of the (too) tiny resistor. So the logic board is wanting to turn ON.
d) Next, is the painful removal of the logic board process. Once the board was dismantled from the (abused) enclosure - observed the regulator for this SSD as follows:
The SSD0 power rail has a normal resistance of ~57R ohms to ground. For this reason, still worth the effort to replace this common point of failure regulator from TI. Part can be sourced from Digikey / Mouser / Aliexpress (suggest in this order). Our DK package is lost in transit but expect it to arrive tomorrow(?). Will update this thread after the surgery.
SSD1 power rail is fine and stable @ 2v5 to ground. Also with ~57R ohms to ground.