[SOLVED]820-2915 ppvcore_s0_cpu

[G.Beard]

Hi.

No visible liquid damage at all. Was told liquid but the board is clean (other than skin flakes, carpet hair and bogies).
No power on.
About 5ohms on PPVCORE_S0_CPU
No working board for reference but I would say 5ohms is too low?.

 

[dukefawks]

5 ohm is fine. The usual PPBUS, 3V3_S5? You using a REAL 85W charger? Battery charging?

 

[G.Beard]

5 ohm is fine. The usual PPBUS, 3V3_S5? You using a REAL 85W charger? Battery charging?

Yes real Apple 85W charger.
Battery... OUCH! fuck me I just picked up the board, found short on U7300 TPS51916 IC itself is burning.

Will try sort that out and get back to you.

 

[G.Beard]

OK, CPU burning my finger now so I'll test board.

3 beeps. I'll check the rest of the circuit.

 

[G.Beard]

Still beeping x3.
1.56V coming from L7330. ALL_SYS_PWRGOD is 3V3... OK I'm lost.

Go back to the start and test power rails?

What should I be testing here please?

 

[dukefawks]

You tried both RAM slots one at a time with known good RAM? If yes then replace Q7330

 

[G.Beard]

You tried both RAM slots one at a time with known good RAM? If yes then replace Q7330

Checked and got 1.56V from L7330.... Still replace Q7330?

 

[dukefawks]

Yes, because the other option is a dead CPU. Do you van RAM slot testers?

 

[dukefawks]

Hold on, you did check 0.75V on pin 3 of U7300 output?

 

[G.Beard]

Hold on, you did check 0.75V on pin 3 of U7300 output?

OK it's working now but

1, I was using carp RAM I found at the bottom of a box so tested with different RAM and OK.
2, I only have one working slot

Any saving that bad slot?

 

[G.Beard]

No image or backlight now.

 

[aprendiz]

if you hear the chime, do a PRAM reset..

 

[G.Beard]

I does chime.
First thing I tried was PRAM reset.

Not getting any signal for LCD_PWR_EN.
Nothing on PPVOUT_S0_LCDBKLT
Nothing on (scope) BKLT_PWM.
No output to external monitor.

No PM_ALL_GPU_PGOOD
U9800 shorted to ground, R8911 in the Mohms range

 

[G.Beard]

OK, had to replace U9800 and stick an LCD backlight fuse where R8911 should be. Working now.... You think fuse be OK in place of a 1ohm to VCC of U9800?
Only one RAM slot working but otherwise looking good.

Anyway to bring the 1 broke RAM slot to life?

 

[dukefawks]

Don't bother, leave it like it is and be happy. Take it to Apple when the GPU dies in 3 weeks.....

 

[G.Beard]

Don't bother, leave it like it is and be happy. Take it to Apple when the GPU dies in 3 weeks.....

LOL, right you are

 

[dukefawks]

It needs to die before 12-31 though, program ends.

 

[G.Beard]

Evil plotting. Mwooohahahahaaa!

And thank you for you help.

 

[G.Beard]

Both RAM slots now working.
Please mark as solved.

Cheers.