820-00165 PPBUS_G3H 0.9v

[MUUK]

820-00165

second post today (sorry no easy boards for me today)

PPBUS_g3h - 0.9v short to ground.

removed f7700 - short not on LCDBKLT side
removed f7140 no short on pin 1 (if apply power with this removed voltage is 8.5v)
short to ground on system side (pin 2 F7140 onwards)


tried removeing q3080 no change
removed q5500 no change.
replaced u7100
removed C7582 C7540 as got hot, no change
removed R5450 -went from diode mode 0v drop to 0.022 drop with R5450 removed ppbus_g3h goes to 7.4v
replaced with donor R5450 get short again (0v drop diode mode pin2 F7140)

looking on my schematic i can't find R5450 - although it is present on the board. Looks like its labelled R5400 on the schematic.

Tried removing U5450 (brd) U5400 (schematic) no change

Injecting voltage it took 2A and 0.6v and Q7430 got boiling hot, i removed it but the short still remains.

Any suggestions gratefully received.

 

[aprendiz]

Measure resistance between PPBUS_G3H to L7310 and L7320, there is a big chance that this board is a donor board now......

 

[larossmann]

All of the haswell quad cores are complete pieces of shit when it comes to liquid around the edge. The slightest hint of liquid and CPU shorts PPBUS_G3H to ground.

 

[MUUK]

Thanks guys. Resistance (not diode mode) between pins 1 on 7310 and 7320 and PPBUS_G3H (F7140) is 22ohms. Diode mode voltage drop to ground on pins 1&2 of L7310 and L7320 is 0.012v

 

[dukefawks]

I can say quite certain this board has been thoroughly fried, rabbit hole to hell, avoid.

 

[MUUK]

Ok. Thanks Duke.