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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Note: You may check out his previous post in the below links:

https://jestineyong.com/bad-viper-12-a-power-ic-in-induction-cooker/

8 Comments

1. 

   Albert van Bemmelen

   February 7, 2020 at 8:39 pm

   Good job Suranga, but what exactly made you suggest that the power IC was still good after seeing all connected components that needed to be replaced?

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   • 

     Tayo

     February 7, 2020 at 11:59 pm

     I have the same question as well. Especially when a bad power IC could blow his newly installed component(s) again. Perhaps Suranga couldn't get his hands on a replacement IC and decided to roll the dice. But, from my experience, a blown MOSFET is often indicative of a signaling problem so replacing the IC is par for the course. Also, that IC could be failing intermittently. Works today... misfires tomorrow. But Suranga has a lifetime more experience at this than I do and is probably in no short supply of caps, resistors and mosfets to replace these with in case they did blow up again. But still I'd love to know what made you take that chance.

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     • 

       Yitbarek

       May 8, 2020 at 1:48 am

       I have related problem with ic2030.in My HIFI home theater,one ic2030 have blown and I replaced with the same ic,but when I hook the bass speaker the replaced ic become overheating, where as the other ic normal,what can you suggest me to over come this problem please!!?

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2. 

   Parasuraman S

   February 7, 2020 at 8:46 pm

   That was a nasty blow to the power supply and surprising that it withstood! But let it be anything, when it comes to you, it would get a life and that is your creditworthy service!

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3. 

   Lynn Blakely

   February 8, 2020 at 3:16 am

   Good job Suranga, That FET shorted may have saved the power IC, plus the fuse opened quickly, did it's job.

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4. 

   Yogesh Panchal

   February 8, 2020 at 3:33 pm

   Good job! Suranga.
   Agree with lynn Blakely....just confirm for the short circuit of IC if not - take a chance.

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5. 

   ulises aguilar

   February 13, 2020 at 12:59 pm

   good job Sir and happy new Year

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6. 

   Justice

   August 5, 2020 at 5:12 pm

   Good work Suranga thanks

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