Test Laptop AC Adapter
Step 1- Disconnect the power power cord.
Disconnect the plug from the wall and the computer as you will be testing the wires for continuity.
Step 2- Disconnect the power cord from the AC adapter power supply.
Disconnect the power cord side from the AC adapter side. Now you have two separate pieces, the power input cord, and the power supply with the thinner cord that plugs into the laptop.
Step 3- Test resistance though the plug prongs.
Connect your meter while in the Ohms setting to the two main prongs on the power cord. With the cord isolated from the power supply, you should get an open or infinite Ohms. Note: If your adapter does not disconnect in the middle, then you will be reading through the power supply, but you should still get an open on the test.
Step 4- Read from plug ground to outer shell of laptop side.
Connect the power cord and AC adapter together again. Connect one meter lead to the ground prong of the wall plug, and the other meter lead to the outer shell of the laptop side plug. You should get a reading of continuity here, or zero Ohms. If you don't, then your ground is defective.
Step 5- Be sure the cord is not plugged into the power outlet.
STOP: Make sure the cord is not plugged into the wall, severe shock could occur or meter damage.
Step 6- Jumper the inner contact of laptop side.
Make a jumper wire that will fit into the adapter tip. You can also wrap a piece of safety wire around the meter lead, and use that to insert into the contact.
Step 7- Test for a short on laptop side contact.
Check for a direct short between the outer shell and the inner contact of the laptop side plug. You should read an open on this measurement.
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