ATTENTION: Opening the AC adapter means you are voiding the warranty provided by Apple. In case of any accidents, fires or mishap, you will hold me harmless against all liabilities, lawsuits, etc.
Work Steps that I’ve taken
We will desolder the two terminals in this part. The original Apple ac adapter has a green wire soldered to the positive (+) and a black wire soldered to the negative (-).
My replacement charging cable used white colour to denote the positive terminal and black colour to denote the negative terminal.
We need to verify the replacement charging cable’s polarity before soldering the replacement cable onto the adapter.
To do so, connect the probes from a multimeter with continuity function or continuity checker to the charging points. You should get a similar pattern to mine (illustrated below)
Now that you have ascertained the polarity. Time to desolder the old charging cable. Let us have a quick recap on the terminals we need to desolder.
Using the soldering iron, heat up each point at a time and remove the flux using the solder sucker / desoldering wick.
You should get this. Two clean circles where the original points were .
You will be able to see this from the underside. Notice there is white gunk surrounding two connectors, you should not see this if you didn’t remove the gunk – and you should not remove this ‘gunk’.
Soldering the replacement charging cable back on the two terminals.
Testing time. But first to put the adapter block back into the casing. Remember to cover the two re-soldered terminals using the orange tape.
Gently slot the adapter block back into the white casing, as shown below. Note there are grooves in the replacement charging cable stopper (flange) that needs to be aligned with the two halves of the plastic casing for a good fit.
Lets see if it works.
Next to Part 4 for adhering the two halves of the adapter together.