How to fix a Power Supply.

Got an email from a long lost friend asking how to fix a Power Supply?
His Question is.......
My Canon Fax broke down yesterday.
After using it for four years, it finally dies off.
No power lights... nothing at all.
So I fetched my toolbox and finally dismantled out the power supply unit.
Took a look at it and found the fuse shorted black in color.
Replaced the fuse, switched on and it blows again.
What shall I do next?

My answer to him was.......
When you checked the fuse, take a good look at it.
If it is burnt black, there's always some other components shorted as well.
You have to do a throughout check.
If you find the fuse is open but it is colorless or slightly yellowish,
that means you can straight away replace the fuse and test out the machine.
WHY? because the yellowish open fuse dies off due to old age.

Well, when I get a reply from him again, I will let you know the rest of the story.