[SOLVED]820-00164 no power

[Jay]

820-00164 has a light on the magsafe but no power. No liquid damage or other kind of damage.
PP3V42_G3H is 3.4V at L7095
PPBUS_G3H is 0V at several places I measured.
Checked for a short to ground and get 0.001 - 0.000 which means there's a short right? (never dealt with a short to ground before).
Now I don't have a power supply to inject voltage and see what gets hot so what would be the best way to go about tracking down the short?

 

[dukefawks]

You should go and get a power supply, it is a pretty essential piece of kit.

 

[Jay]

Alright, just ordered one. Anything I can do in the mean time?

 

[dukefawks]

Not unless you want to rip off every component on PPBUS, you can inspect all the caps for signs of damage.

 

[Jay]

Got the power supply, looking for usage tips. Can't find anything good in Louis' channel or via google. + - and GND, GND is self explanatory but other wire goes to + or -? Will stick to voltages and amps as displayed on OEM Apple power brick depending on model but if Louis did a video on this that I just can't find or if there is a good writeup on how to use a power supply to find a short and how to wire it up, that'd be great. Also, got several magsafe plugs here I want to use with this external power supply, again need to know if I use + or -. I read mentions of + but prefer to take the word of someone here with experience over Wikipedia

 

[dukefawks]

- to GND of course and + to the shorted rail. Then start at 0v and slowly increase and monitor current draw. Of course NEVER go over the voltage that the rail normally receives. At 1-2 Amps something will usually start heating up.

 

[Jay]

Thank you Duke, will tinker with it this weekend

 

[Jay]

Injected power, up to 8.6V at 2.5A, nothing gets warm. Power supply outputs no more than 00.30V at those settings. This is the second board I inject and the second one that does not get warm, am I doing something wrong here? - to GND and + to the shorted rail, as you said. In this case + goes to R5430 pin 2. Heatsink is off of the CPU too. You mentioned something should heat up at 1-2amps so I am hesitant to go higher than that, can I go higher though? And how high can I go?

 

[Jay]

Thanks to a tip from jadao on another post, Found the short. Had to set the Amps to max (5.1) and then start raising the Volts.