Idle voltage at 17 Volt instead of 6.8 V after changing MagSafe cable

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Albert Emil @albertemil

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发帖于: 2019年6月16日

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Idle voltage at 17 Volt instead of 6.8 V after changing MagSafe cable

I replaced my broken MagSafe 1 cable with a replacement cable and get some weird idle voltages:

After desoldering the broken cable from the two pins on the PCB, I checked the idle voltage. My multimeter gave me a reading of 6.84 V which is in accordance to the ifixit guide and Wikipedia.

However, after attaching/soldering the replacement cable to the two PCB pins, I get an idle voltage of around 17 V. As far as I understand, this is the regular charging voltage at load, but not at idle. Since I ordered two of these replacement cables, I tried the other one, but got the same result: ca. 17 V at idle.

My MacBook Pro is charging with the repaired cable, but does not light up the green LED inside the magnetic connector when fully charged. I assume that this is due to the power supply not reducing the voltage to the required 6.8 V at idle.

Does anyone know how to fix the idle voltage and get proper charging behaviour?

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Dan @danj 声誉积分: 479.3千 Self employed contract worker 35 329 971 · Answer 1 · 2019-06-16T05:38:25-07:00

I personally don’t recommend trying the fix the charger.

Theres a bit more going on here than meets the eye! The MagSafe connector has a small circuit which ID’s the wattage of the charger so the cable you got is likely not the correct value. Here’s a bit more Teardown and exploration of Apple's Magsafe connector

These cables are very suspect! As Apple never offered any parts for the charger and these cables are either recovered from the cloned MagSafe chargers or may not even have the needed circuit which could put your system at risk of damage! OEM MagSafe Chargers vs Cheap Imposters: Teardown for Truth

Don’t get me wrong here Apple’s MagSafe charger design should have had a removable cable from the get go! Like what we now have with the USB-C charger design. But, even its design is flawed! As what made the MagSafe design so good was the break-away connection on the system which is now missing on the USB-C systems.

So Apple went from bad to bad! Maybe the next systems fix this failure.

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Idle voltage at 17 Volt instead of 6.8 V after changing MagSafe cable

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