820-00923 pulsing S5 rails

[ajdoc]

Board clean.

PPBUS_G3H 13.05V
PP3V3_G3H 3.4V

PP3V3_S5 and PP5V_S5 voltage pulsing.
lifted one side of L7660 and PP5V_S5 is stable (both side of L7660 stable 0V) so fault is on 3V3 rail?

Diode mode values:
PP3V3_S5 0.350
PP3V3_SUS 0.327
PP3V3_S4 0.326
PP3V3_2V7_NAND_VCC 0.304
PP3V3_S0 0.290

Any idea?

 

[2informaticos]

820-02016 board doesn't have Intel parts.
How did you find PPBUS_G3H in that schematic???

 

[ajdoc]

Sorry - I enter wrong board model.
Correct board model: 820-00923

 

[2informaticos]

Disabling 3V3_S5, power on sequence breaks.
That doesn't point to a failure related with 3V3_S5.
The problem can come from other secondary power supply, in S3, or S0 state.

Check diode mode to ground on all coils; compare with good board.

BTW, did you test in SMC bypass mode?

 

[ajdoc]

Hmmm Dont know why but have stable PP5V_S4 and L7600 gets hot (85C, 5V and diode mode value correct)
Replaced L7600 and is not hot anymore.

With battery connected I have 20V 2.85A (board only 20V 1A) so system 'boots'? and battery is charging, fans spins.
Caps lock not workig, no chime, CPU warm. Target Disk mode not working.
PPVCC_S0_CPU 1.14V
U7210/20 warm (65C)

 

[2informaticos]

When board really boots, CPU core voltage should drop to 0.65V aprox.
PCH, CPU and BIOS are involved in this process.