What voltage readings should I get from my 60 watt Magsafe if I check the pins with a multimeter? My readings are all below 1 volt (I checked all combinations of pins), but I don't know if this is correct since there is no load. Also what pins should I check? My computer is a MacBook Pro 2011 early model.
MacBook – What voltage readings should I get from the 60 watt Magsafe
macbook promagsafe
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Best Answer
A good description can be found at Teardown and exploration of Apple's Magsafe connector
Below is taken verbatim from the above link.
The charger startup process
When the Magsafe connector is plugged into a Mac, a lot more happens than you might expect. I believe the following steps take place:
If the Mac is happy with the charger ID, it switches the power input to the internal power conversion circuit and starts using the input power. The Mac switches on the appropriate LED on the connector using the 1-Wire protocol.
This process explains why there is a delay of a second after you connect the charger before the light turns on and the computer indicates the battery is charging. It also explains why if you measure the charger output with a voltmeter, you don't find much voltage.