Mid 2010 MacBook Pro 15" will only charge with one charger

[jpow112]

Hi -

My reserve machine, which works well otherwise, is very fussy about chargers. It will only charge with a particular 3rd party charger. It won't charge with its old original charger, or any others. The original charger will however charge any of my other macbooks without a problem.

I've tried reseting the SMC, without effect.

Any other ideas?

 

[craig1024]

How dirty is the MagSafe port try cleaning the connectors also check if something is preventing the charger from going in all the way.

 

[jpow112]

I'll have a look at the ports with a magnifying lens - I guess there could be a physical difference between different chargers. Is there any handshaking with chargers, or is it purely a DC current?

 

[Awjvail]

I'll have a look at the ports with a magnifying lens - I guess there could be a physical difference between different chargers. Is there any handshaking with chargers, or is it purely a DC current?

There absolutely is handshaking with the devices. The magsafe performs a handshake before any power is delivered.

When the Magsafe connector is plugged into a Mac, a lot more happens than you might expect. I believe the following steps take place:

1. The charger provides a very low current (about 100 µA) 6 volt signal on the power pins (3 volts for Magsafe 2).
2. When the Magsafe connector is plugged into the Mac, the Mac applies a resistive load (e.g. 39.41KΩ), pulling the power input low to about 1.7 volts.
3. The charger detects the power input has been pulled low, but not too low. (A short or a significant load will not enable the charger.) After exactly one second, the charger switches to full voltage (14.85 to 20 volts depending on model and wattage). There's a 16-bit microprocessor inside the charger to control this and other charger functions.
4. The Mac detects the full voltage on the power input and reads the charger ID using the 1-Wire protocol.
5. 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.

The complex sequence of steps provides more safety than a typical charger. Because the charger is providing extremeley low current at first, there is less risk of shorting something out while attaching the connector. Since the charger waits a full second before powering up, the Magsafe connector is likely to be firmly attached by the time full power is applied.

http://www.righto.com/2013/06/teardown-and-exploration-of-magsafe.html

 

[jpow112]

Interesting stuff.

What confuses me is that the third party charger works, but not the official one. Apart from a physical difference with the pins, I can't imagine why a handshaking protocol would reject the more legitimate charger.

 

[tubeexperience]

You might need a new MagSafe DC-In Board.

 

[jpow112]

is that the small magsafe port here?

https://eustore.ifixit.com/en/Parts...through-Mid-2012-MagSafe-DC-In-Board-New.html

 

[Fishrrman]

I'd say, "use what works for you", and be happy with it.