820-00239 dead ppbus cycling.

[Yoel Ren]

Hi, this board came in dead. board pristine, just a bit of dust.
when magsafe plugged in, its taking 20v 0.03Amp which cycle to 0 amp every few sec.
ppbus_g3h is around 3.8v, but every few second cycling to 13v for a split second then back to 3.8v
is this some kind of mosfet or u7000 problem ?
pp3v42 : 3.42v
i tried all port same behaviour.

 

[Yoel Ren]

ppbus isnt shorted on either side, and has diode mode of 0.400 with fuse attached.

 

[2informaticos]

Check for short on all big coils.

 

[Yoel Ren]

l7410 L7420 and l7430 is 2.5 ohm, is that normal? Other than that, theres no short on any other coil.

 

[2informaticos]

CPU has low values on its coils; you should compare readings with similar board.
Check for voltage pulse on all coils, at same time when PPBUS_G3H pulses to 13V.

Remove F7000 and check if get stable C7050 voltage.

 

[Yoel Ren]

ok somehow ppbus isnt cycling anymore,
but voltage doesnt go past s5.
ppbus_g3h 13v
pp5v_s5 5v
pp3v3_s5 3.3v
pp3v3_sus 3.3v
s5_pwrgd 3.1v
pp5v_s4 0v
pm_slp_s5_l 0v
p5vs4_en 0v

 

[2informaticos]

Trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L, at same time.

 

[Yoel Ren]

do you do this to make sure board receive signa to turn on ?
voltage 3.3v, when onoff shorted, pm_pwrbtn_l drop to 0.3v..

 

[2informaticos]

Now check if PM_SLP_S4_L pulses at same time...

 

[Yoel Ren]

while checking that, somehow mac improve itself..
voltage now is stuck at 20v 0.26amp, trackpad can click, but no brain
pm_slp_s4_l is 3.3v
ppvccsa_s0_cpu 1.05v
ppvcc_s0_cpu 0v.
pp5v_s0 5v
pp3v3_s0 3.3v
all_sys_pwrgd 3.3v

 

[Yoel Ren]

any pointer?

 

[2informaticos]

Try known good BIOS.

 

[Yoel Ren]

I dont have ppvcc_s0_cpu..
regardless I use another bios but turn out exactly the same behaviour.
pm_slp_Sus_l 3.3v
pm_rsmrst_l 3.3v

 

[Yoel Ren]

so im using thermal cam and see that c7714 is heating up.
voltage is 3v.
i replaced c7714 and c7708 which is also heating up, but voltage is 6v now.
i use same donor board to replace it.
how can I control the voltage to 1v ? ( the good value )

 

[Yoel Ren]

r7732 is broken, replaced, now 1.05v at c7714.
but still no ppvcc_s0_cpu

 

[2informaticos]

Did you really get 3V, next 6V at CPU core?
If yes, CPU is dead now; even if was for few seconds only.
I suppose it was a bad measurement only.

 

[Yoel Ren]

its a ppvcedram_s0_reg_f, does it count as cpu core too ?

 

[2informaticos]

Is the power rail for the internal CPU EDRAM.