Surprised That The Power IC Did Not Blow
This Konka 24″ LED TV was sent into my workshop for repair with the complaint of no power. Although no power symptom usually related to the issue in the power supply, it can also caused by bad mainboard. The reason for it is the front power LED signal is coming from the mainboard and not the power supply.
This means if the power supply is good and the mainboard is bad there will be no light at all from the power LED.
Once the cover was removed, the first thing I did was to look at the main fuse and it was burnt in darker color.
When the main fuse burnt (seethe above photo), the next component that I wanted to check was the bridge rectifier and the power FET. The bridge rectifier was working fine but the power FET was shorted when tested the leads on board.
For your information I almost missed the main capacitor. It was slightly bulged! I also found the current sense resistor had a crack at the out layer but the power IC was intact.
Usually in this kind of situation I would just direct replace the power IC and retest it but in this case I have decided not to replace the power IC AND retest it and see how it goes.
I was really surprised that the power supply came back to life. Even though there are four components already bad and the power FET was shorted, the power IC remained good!
Conclusion- Assuming after powered On and the power supply still refused to work, I would replace the power IC and retest it again. If you would like to be able to troubleshoot and repair power supplies effectively I can recommend Jestine Yong Ebook’s on power supplies repair. You can click here to check it out.
This article was prepared for you by Suranga Bandara who owns an Electronics repair shop in Anuradapura, Sri Lanka.
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