An old man brought his laptop and the power supply for repair. For some reason, the laptop was not powering on. It could be either the power supply or the laptop itself has problem. I tested the output voltage on the power supply and I got a reading of 22 volts. The output voltage should be 19. From experience, I knew the problem right away. The main problem was the power supply.

An easy way to pop this power supply open is to use a sharp knife and follow the line around it. When done the right way, you can use four drops of super glue on the corners of the two sided plastic covers to glue it back together.

Once I cut it open with nice straight line around the power supply, I could see the inside of it. One side of the power supply shield was soldered to ground. Once I de solder that side, the shield will come right of.

A quick look and I can see that all capacitors are in good shape.

Once I de-soldered the shield off and looked to the other side of the board, this is what I found. The line that goes to the AC line to the bridge rectifier is slightly broken. It was very hard to find. I have used my new microscope to check it out. I used an isolated wire that I took out of an old transformer. They are the best wires to use. They are isolated and I can scrape the edge of it when I solder it to the board.

Remember I mentioned before that I was reading 22 volts? That was a fake 22 volts. They do not exist when a load is applied to the power charger. For example, I put a car light bulb that works on 12 volts and the light bulb did not come one.

After fixing the trace I could see 19 volts and steady. I put a light bulb to the negative and positive terminals of the power supply. The light came one.

I connected the output wire to the laptop and I could see the laptop coming on.

Mission Accomplished.

This article was prepared for you by Waleed Rishmawi, one of our ‘Master Authors’ and currently working in the Bethlehem area of Palestine repairing electrical and electronic equipment.