8203787 won't turn on

paky

New member
Hi guys, I have this mac that does not turn on, green led for 1 minute and then orange. I had an absorption of 0.22 and after replacing u7100 it dropped to 0.8. but still does not start. Some idea?
 

2informaticos

Administrator
Staff member
First of all, welcome to the forum.

We need some voltages and signals from power on sequence.
Magsafe light should switch faster from green to amber (in seconds).

Post exact voltage for PPBUS_G3H and 3V3_S5/SUS, if appear.
 

2informaticos

Administrator
Staff member
Post exact resistance to ground at PPBUS_G3H (ohm scale).
Allow 10-15s after power is removed, before measure ohm scale.
 

2informaticos

Administrator
Staff member
Do you mean 0.4 ohm (400 miliohm)?
That is pure short.
Check if you get same value in any big coil, from secondary supplies.

0.4 in diode mode is totally different thing...
 

2informaticos

Administrator
Staff member
What do you expect then, apart of pure short?

"Post exact resistance to ground"
Was not this clear enough?

Please post again all values; measure between corresponding coil and ground!
 

paky

New member
sorry I misunderstood
L7130 25.4
L7430 250.2
L9330 32.4
L9360 35.8
L7320 20.7
L7330 20.4
L7130 0.3
 

2informaticos

Administrator
Staff member
Then is safe to inject voltage, if short remains on PPBUS_G3H.
Start with 1V and go high slowly, if needed.
Set first the lab PSU amp limit to max.
Probably a big cap will heat on PPBUS_G3H.
 

2informaticos

Administrator
Staff member
Lower the voltage, to keep current bellow 5A.
For such pure short (0.3 ohm) you need powerfull PSU.
20A models posted on the forum.
 
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