[SOLVED]820-3437 PPbus_g3h unstable/pulsing

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Hi,
I've got a 820-3437 board here that won't turn on. Magsafe light is on, but nothing else happens. PPBUS_G3H is around 8.56 volts but isn't stable. Replaced ISL6259, didn't help.
Any suggestions where to look next?
Thanks, Rick
 
R7105 measures fine. Tried the machine with it's own battery (status unknown) and this seems to stabilise PPBUS_G3H at 8.67V. I'll try and find a properly charged battery next. Any suggestions as to what this means and what my next step would be? Kind of lost on this one.
Thanks, Rick
 
Nope, know good battery doesn't change a thing compared to above. So info so far:

* PPBUS_G3H is around 8.56 volts but isn't stable (stabilises at 8.67V with battery attached)
* Resistance ISL6259 (replaced):
- 17/18: 3 ohms
- 27/28: 20 ohms
* PPDCIN_G3H: Varies slightly between 16.65 and 16.66v (stabilised when ISL was removed)
* No S5 rails present, they are fluctuating because of PPBUS_G3H. None of them are 0V.

Any suggestions?
 
Never mind, I just fixed this one. PP5V_S4RS3 was shorted on C7553. Repealed and replaced it and now it's working again. Thanks for your suggestions people.
Cheers, Rick
 
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