Retina 15" Late 2013 820-3787-A Green/Orange Light on Magsafe no fan

[Razertech]

Hi everybody,
I'm working on a retina board for a graphic issue at the begining
So I reflowed the U9300 and after that at first boot fan for 3 seconds then stop and now nothing,

I checked

U7100 between 17 and 18 = 3.5Ω
U7100 between 27 and 28 = 21.5Ω
U7100 PIN2 = 20V

PPBUS_G3H = 1.67volts
PPDCIN G3H = 20,43v
PP3V42 G3H = 3.43v
PP5V_S5 = 0.851v
PP5V_S0 = 0.455v
PP3V3_S5 = 3,3v

I can't find a solution for this board I can try to replace U9300 but do you think that this component can cause this ?
Or something else is burned now ? I used a Chinese adapter so perhaps that have nothing with U9300

Thanks for help

 

[phuketmymac]

PPBUS_G3H = 1.67volts

Should lead you to think you have either a short on that rail or the ISL is bad...

 

[Razertech]

Yes I will try to change it,
but I have also
PP5V_S5 = 0.851v
PP5V_S0 = 0.455v

So I have to change Both ISL U7501 and U7100 ?

Or this problem can be caused by U9300 as it's the only thing touched on this motherboard before this failure.

Thanks for help

 

[JohnB8812]

Resistance to ground on PPBUS? If U9300 was messed with, this could be bad.

 

[Razertech]

The resistance on PPBUS_G3H is 19Ω
The U9300 seems to have been resoldered correctly when I check on the microscope everything seems to be perfect.

 

[2informaticos]

Do you get the same value (as PPBUS_G3H) on any big coil (from secondary supplies)?
You can also lift F7140/41 to see where the low value remains.
Do not power up the board again, untill find the culprit...

 

[Razertech]

Ok so I have changed U7100 and problem is the same
Green light and orange light with no fan.

I've Lifted F7140 and 7141 and resistance to the ground of PPBUS_G3H is 16.4Ω

Where are the coils from secondary supplies ?

Thank you really much for help.

 

[Razertech]

So I removed U9300

When I remove R5400 the short is still there on PPBUS_G3H with 17.8Ω

and not anymore on PPVIN_S5_HS_COMPUTING_ISNS

But I've a short on PPVIN_S5_HS_GPU_ISNS => 18.6Ω
There is a short on PPVIN_S5_HS_OTHER3V3_ISNS => 19Ω
There is a short on PPVCC_S0_CPU_REG => 20.7Ω

 

[dukefawks]

Measure resistance from PPBUS to all coils starting with L9330. I bet there is a 0 Ohm short there.

 

[Razertech]

Hi Duke thanks for your answer, you're right, I checked and there is a short between PPBUS_G3H to L9330 I found 0.5 Ohm
What's the solution ?

 

[dukefawks]

Replace U9300 and Q9330/31 and pray the GPU wasn't killed by the 12V it got.

 

[Razertech]

ok so I replaced U9300 + Q330/31 The fans was spining, no shorts anymore, so I tried to reput the board into the computer , and again no fan , with the same short than before.
I don't understand how it's possible.
Do you have an idea Duke ?