I acquired this Apple //c with issues from a local collector without any power adapter.
The Apple //c is powered with a 7-pin DIN connector, according to apple specs, 12v to 21v volts, about 2A max at 15v.
The barrel jack on the USB-C PD cable was cut and replaced with a DIN connector; both were bought from TaoBao. The cable’s output was 12v even though the website says it is 20v; either way, it is within working range.
The rubber shield of the DIN needs to be sanded down to fit the //c connector due to the poor production of the connector I bought, as I don’t have a problem with other 3rd party power bricks.
Overall, this mod makes the Apple //c portable and runs for about 2 hrs with a 10,00mAh battery. I might replace the DIN power connector with a USB-C socket to reduce the bulk and use regular USB-C cables.