[SOLVED]820-00164 no power

Jay

Member
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?
 

Jay

Member
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 :)
 
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dukefawks

Administrator
- 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

Member
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

Member
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.
 
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