820-00138 not start

[Dozer]

hello friends

i just work on this board. it came in with"liquid damage" but i looked the whole board and nothing to see, its not cleaned.

i found a short PPbus_G3H to GND, After replacing U7310 i got a fanspin, but still no cpu vcore.

CPUVR_FCCM is zero. It has to be zero? in schematics is a inverted input to see.


ALL_sys_pwrgd (VR-on) is 3.3V on u7200, VDD and VIN is ok.

so is u7200 working?

SCLK is no clock to see in this moment.

need some assistance please what could be the next step.

 

[2informaticos]

If ALL_SYS_PWRGD is high, you should have voltage on all coils; maybe not on CPU ones.
Do you get voltage at pins 7 & 3 of U1950?

Damaged U7310 probably denotes dead CPU.
This looks like hopeless project...

 

[Dozer]

is it possible to get on U1950 pin 7 a High if CPUVR-PGOOD is LOW ?

 

[JohnB8812]

Dead CPU RIP. U7310 sent 12 volts to the CPU this is done.

 

[Dozer]

so if the cpu would be not dead there would be a clock on SCLK to see?

the short was in u7310, that was going hot, the cpu was not hot or warm.

 

[JohnB8812]

U7310 is the high side CPU controller. If it was shorted, it stopped turning 12.56 volts into 1.8 volts for the CPU and was sending 12.56 volts to the CPU. The CPU saw 12.6 and was instantly killed. You're wasting your time on this one sorry.

 

[2informaticos]

"is it possible to get on U1950 pin 7 a High if CPUVR-PGOOD is LOW ?"
Yes, because pin7 should go high first, in order to enable CPU power supply.
Pin 3 goes high only after VCORE is confirmed.

Your CPU has less than 1% chance to survive; case closed, don't waste more time...

 

[Dozer]

ok, thank you friends for your help, so i will give it back to customer. You saved my time.