No Power in ATX Power Supply Repaired-3 Components Replaced
Received one Desktop PC with no power symptom- diagnosed as follows:
Checked power cable found ok with 230 v at the other end, checked computer ON/Off switch found ok. There was burnout smell in the SMPS and I concluded the problem is in SMPS and not in the motherboard. Now disconnected the SMPS from Motherboard and took it out for further diagnosis. After opening the case I used a blower to blow away the dust.
After cleaning I did not find any burnt mark on PCB. As for the main fuse, it was blown into pieces. Next, with my visual inspection test with the help of a magnifying glass, I saw one burnt resistor- see the photo below:
I began to check on the components in surrounding area and I have found one Mosfet CM 2N60F and STC945 NPN transistor open circuit. If you want to learn how to check electronic components, you can check out Jestine Yong’s ebook HERE. Below is the location of the bad components.
Here are the three faulty components:
I replaced the parts and tested it using a 100 watt bulb to make sure no more short circuit in the circuit board. I had to connect it to a ATX power supply tester. The result was good because the bulb lights up for 5 seconds and then went off. The fan started to turn. After that I checked on the output voltages and all were within range.
Once I found that the power supply was working fine, I turned off the supply and removed the light bulb and put in the main fuse. I then assembled back everything and retested again the power supply before sending it back to the customer.
This article was prepared for you by Yogesh Panchal who works as a Computer Hardware Engineer in Mumbai India.
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