[SOLVED]820-3115 No V-core

[ALB-Repairs]

820-3115 with no V-Core.

Origianly damage to the TON resistor (TON A AND TON B) Replaced these resistors and U7400.

The resistor values are correct but pin TONA and TONB is 0v

ive seen this caused by the pch before but this isnt a 100% certain solution as i have tried on other boards and not made any progress.

Enable and VIN are both present.

 

[arghhh]

So the fan spins on this board and you have a green light? What's the voltage on PPBUS_G3H?

 

[ALB-Repairs]

Yes, Yes and 12.6V

We are only looking at the V-core circuit. We have ALL_SYS_PWRGD, which is one of the last signals to come up before the V-Core circuit is enabled.

 

[arghhh]

Well TON comes from PPBUS_G3H, so check for a broken trace to those resistors.

What's the voltage on either side of R7402/3?

 

[ALB-Repairs]

The Traces are normal. 12.6V on the PPBUS_G3H side, 0V on the TON-A and TON-B sides.

 

[arghhh]

Remove U7400 and see what the voltage is then.

 

[arghhh]

No I haven't but I will take your word for it. What's the voltage on CPU_PROCHOT_L?

 

[dukefawks]

Resistance to GND on pin 1 of R7402/3. Are you sure there is 12V on pin 2?

 

[larossmann]

For me it's always some corroded solder ball under PCH if not U7400 that reflow fixes. It's hard to see under that chip with a microscope due to position.

 

[ALB-Repairs]

Physical damage by previus owner. L2451 replaced L2406 replaced. Both supply the PCH with voltages.

all problems solved.