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[SOLVED]820-3437 PPbus_g3h unstable/pulsing

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rvanpruissen

Member
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
 
R

rvanpruissen

Member
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
 
R

rvanpruissen

Member
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?
 
R

rvanpruissen

Member
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 Repealed and replaced it and now it's working again.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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