820-2915-B: 8V on PP5V_S5

[stef4n]

Hello
I started working on a 820-2915-B. When charger was plugged, I had a green light, but no fan spinning and no boot.

C7200 was missing on the logic board. Found the feet of the cap in place but the cap's body was gone. Plus, C7203 seemed partially damaged.
I replaced them, and plugged the charger*.
Fans started spinning, but not chime, no boot. I turned it off.
Turned it on again, took a few measures here and there, suddenly fans stopped spinning.
Almost back to the starting point, but with:
- PPVIN_S5_HS_OTHER_ISNS showing 12.54V,
- pin 1 of C7203 showing 2.5mV. That's too low.
- PP5V_S5. pin 1 of C7205, shows 7.5 to 8.15V. That's too much.
(- pin 2 of U7201 (PP5V_S3_ISNS_R) shows 0.1mV but that's a S3 and I have issues with S5 so not a surprise)
- pin 21 of U7201 (P3V3S5_EN) shows 3.42V
- pin 12 of U7201 (SMC_PM_G2_EN) shows 3.43V
- pin 14 of U7201 (PP5V_S5) shows 7.2-7.6V. That's too high
- pin 20 of U7201, and pin 2 of R7941 (S5_PWRGD) show 3.419V
- pin 26 of U7201 and pin 1 of C7264 (P3V3S5_VBST) shows 7.2 to 8.3V. That's too much too.

U7201 should give the 5V_S3 and 3V3_S5

Dead U7201 ?

Currently not possible to get the fans spinning again. No reaction when pressing ON/OFF.

*Now that I give it a second thought, perhaps should I have wondered why these caps exploded, before plugging in the charger

 

[2informaticos]

"pin 1 of C7203 showing 2.5mV. That's too low"
Should fix that first.
Be sure the trace to pin 22/U7201 is good.

"pin 14 of U7201 (PP5V_S5) shows 7.2-7.6V. That's too high"
That ppoints to bad U7201.
Be sure first to measure correct points and have good contacts.

"pin 26 of U7201 and pin 1 of C7264 (P3V3S5_VBST) shows 7.2 to 8.3V. That's too much too"
No high at all; don't bother with it, once/if you get correct 3V3_S5.

Be sure C7224/64 are good, as their traces too.