Atomrepair
Member
This board has no visible damage. It seemed like a straightforward issue, as I found PP5V_S5 to be shorted to GND. I traced it to C8270, which had shorted for unknown reasons. After removing it, the short was gone, but still no power on PP5V_S5. I replaced U7650 with a good looking one from a donor board. Machine turned on and I got an image on screen, but it shut down mid-boot and wont turn back on.
Measured: PP5V_S5 is 'jumping around'. It has a sawtooth pattern on my scope.
I first suspected U7650 - may have been a bad chip or poor soldering. I took it off and replaced it with another one. No change.
Other components on the PP5V_S5 rail look fine. No liquid or other damage found anywhere.
Measurements:
PM_SLP_S5_L is mostly 0V but has little spikes up to ~1.5V
P5VP3V3_VREF2, S5_PWR_EN, P3V3_S5_EN and S5_PWRGD are all showing a block pattern on scope.
PPBUS_G3H is at 8.7V
Where to from here?
Measured: PP5V_S5 is 'jumping around'. It has a sawtooth pattern on my scope.
I first suspected U7650 - may have been a bad chip or poor soldering. I took it off and replaced it with another one. No change.
Other components on the PP5V_S5 rail look fine. No liquid or other damage found anywhere.
Measurements:
PM_SLP_S5_L is mostly 0V but has little spikes up to ~1.5V
P5VP3V3_VREF2, S5_PWR_EN, P3V3_S5_EN and S5_PWRGD are all showing a block pattern on scope.
PPBUS_G3H is at 8.7V
Where to from here?