I have received the email below from several people over the years, so I decided to post the answer here:
Dear Sir,
I have Commodore 64k computer. which power supply is damaged and i cannot find new one in Pakistan . so please send me circuit diagram of power supply so that i can made it.
C64 power supplies are plentiful almost everywhere in the world. I suggest you try eBay or your local thrift store. They are worth very little.
However, if you really need the diagrams here is the "internal power supply":