820_3115 b a1278 No power

syslan

New member
Hello,
When it got here the first time Trackpad was not working so we inyected voltage to u5805 , Got hot , after that , the mb stopped turning on.

have this Right Now
- Green Light on
- PSU consumes 0.01A
- PP5V_S3= 0
- P5VS3_EN_L=3.42 , but P5VS3_ENTRIP=0
- 5V3V_REG_EN= 3.22 , but PP5VS5_LDO=0
- P5VP3V3_REG3=0

What could it be?
Is it possible to turn it on without u5805
 

2informaticos

Administrator
Staff member
First of all, welcome to the forum!

Injected voltage on U5805 which pin and why???

Post diode mode to ground at 5V_S5.
If short (or low value), remove R5805, L5800 and check again.
Do you get 3V3_S5/SUS?
 

syslan

New member
Thanks for the welcoming.

Injected in pin 1 to see if it strated to get hot. Which it did.

5V_S5 is not in Short . value reads 630 in diode mode.

3V3_S5/SUS = 0.36
 

2informaticos

Administrator
Staff member
Do NOT inject voltage without reason for the future.

Post basic voltages for U7200; pins 16, 13, 3, 8, 17, 1, 6.
 

syslan

New member
Update: It turns on but no Video nor USB activity :( . Tried another Bios too and no help.
Im getting theses values.

L7510/20 = 1.12V

PLT_RESET_L=3.32V

CPU_MEM RESET_L=0.67V

mem_reset_L = 1.5V

Is it possible that CPU is bad?
 

2informaticos

Administrator
Staff member
You must discard other options first.

When board really boots, VCORE should drop from 1.12V to 0.78V aprox.
Try one good DDR module at a time, each slot.
Be sure all resistors around U7400 are good, as traces too.
Check all SPI Bus Series Termination resistors and traces.
Finally, heat PCH and/or CPU with good flux; no more than 180-200 degrees, for 15-20s.
 

syslan

New member
Hello friend,

The resistors near the u7400 are all good,

RAM slots are OK!
We also heat the PCH and CPU.

Nothing new happend

but Im not sure with the SPI values .

R5120 - 3,20V
R5121 - 0V
R5122 - 0V
R5123 - 3,19V


R5125 - 3,32V
R5126 - 0V
R5127 - 0V
R5128 - 3,16V
 

2informaticos

Administrator
Staff member
You must check ohm value for the resistors and their traces continuity.
Should be good to test RAM slots with dedicated post card.
 

syslan

New member
all resistors are OK , But I was checking a good M.B and got

CPU_IMVP_FBA_R= 0.78 V ( TURNED ON , WORKING MACBOOK)
CPU_IMVP_FBA_R= 1.1V ( NOT WORKING MB)

Is this anything? We also got PPBUS_G3H=12,55v . I dont think this is anything to be concerd off. Im trying to find a Diagnostic Post Card , we did not have one.
 

2informaticos

Administrator
Staff member
VCORE drops from 1.1V to 0.78V when board really boots.
This is a basic test, to confirm CPU is running.

Be sure to test with known good BIOS.
 
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