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Shorted Cap In Scalar Board Caused No Display In SONY LED TV KLV-29P423D

By on May 27, 2023
led scalar board repair






led scalar board repair

This TV was picked up by me from one of my techie friends’ shop, as he sought my help to resolve an issue of no display, with VGH & AVDD missing. As he had already opened and cleaned the set, it saved my time.

The booster IC used in this TV was, data of which was obtained from my techie group: CM508 ic

Now let us have look at the scalar PCB and bit of inside for those who might be interested:

cm508 scalar board

My techie friend, who always helps and guides me, told me to first of all isolate the concerned pins and its delivery end to the panel and check for any short either in the IC, Panel or that track.

I isolated the panel at the extreme end where it goes to panel and did not get a short in the panel. So rejoined it. Then isolated the track from the IC:

how to fix led scalar board

The short was traced to the rest of the track, which had series of SMD caps. In order to find out which was the culprit, my friend suggested applying 5V 5A to the track, after rubbing soldering flux on all the caps in the track. I saw one cap fuming when I did it and easily located it and removed it.

shorted smd capacitor

As you can see, it was reading 12.2 Ohms! I took one such cap of around 10uF and fixed it in the place.

Reconnected the tracks and applied power and was happy to see Sony logo displayed on the screen:

sony display led

Fed my usual Video of Sherlock Holmes and allowed the TV to run for several hours before giving delivery to my friend.

how to fix a broken scalar board son

Mission accomplished with double satisfaction gathered to the collection!


This article was prepared for you by Parasuraman Subramanian from India. He is 72 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.

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You may check on his previous article on Loose Contact In Power ON Button Caused Dead Condition In Mr Light Phantom 32




  1. Albert van Bemmelen

    May 27, 2023 at 7:07 am

    Rubbing soldering flux on all questionable smd caps to find the heating up shorting cap fuming is an interesting way to locate the culprit! Although also using a finger to locate the heating up shorting low resistance cap is a good method too.

    • Parasuraman S

      May 27, 2023 at 4:11 pm

      Many thanks for your comments and observations! I am always hesitant to touch components with my finger, especially when the boards are such.

  2. Mark

    May 27, 2023 at 1:57 pm

    Well done Parasuraman as usual.
    Interesting technique to find the shorted component. I'll remember that for another time

    • Parasuraman S

      May 27, 2023 at 4:12 pm

      Many thanks! All thanks go to my techie friend who is always ready to find a way out for me, whenever I grope in dark!

  3. Waleed Rishmawi

    May 27, 2023 at 2:59 pm

    yes very interesting approach to finding shorts. This month I purchased a thermal camera to help me in such issues. yes it is expensive but worth having. already helped me in many laptop repair issues or even shorted tv panels. thanks for sharing and have a blessed day

    • Parasuraman S

      May 27, 2023 at 4:12 pm

      Many thanks for your comments and encouragement, dear friend!

  4. Yogesh Panchal

    May 27, 2023 at 11:24 pm

    Good Fix! Sir
    very professional approach for troubleshooting.

    • Parasuraman S

      May 28, 2023 at 10:22 am

      Many thanks, dear Yogesh! All the very best to you!

  5. Tito Kanshulu

    May 28, 2023 at 1:04 pm

    Well done Mr Parasuraman. The method applied is quite interesting. Thanks for the technique

    • Parasuraman S

      May 28, 2023 at 9:38 pm

      Many thanks for your comments and encouragement!

  6. Gregory Brettell

    May 29, 2023 at 1:57 pm

    I wonder if a thermal camera would work as well…

    • Parasuraman S

      May 29, 2023 at 9:02 pm

      No idea! I have not tried! Waleed Rishmawi has mentioned about it in his comments above. Many thanks for your comments!


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