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Is it repairable. TV struck by lightening.

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  • Is it repairable. TV struck by lightening.

    So a friend gave me a free tv. It had been damaged when lightening hit the power line outside his house. It is a flat screen and was about 2 years old at the time. I don't really want to spend anymore than maybe $20 on this thing, but I would like to fix it if possible.
    TV would not power up when I got it. I opened it up and found the internal fuse to be black like the filiment vaporized (to be expected). Other than that, there is only one scorch mark on the board and that component seems to be ok. No other visible damage. I replaced the fuse and plugged it in. I heard one loud "snap" and that was it. Still did not power up. I took it apart again and inspected for damage (again). No visible damage.

    Where do I go from here?

  • #2
    $20 wouldn't repair a transistor radio these days. Check the fuse in the power supply module. You might get lucky. If you have to buy any modules or take it in for repairs, you'll need to dig deeper.

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    • #3
      Forget it. If the fuse blew from a surge then most likely every semiconductor is toast. I have seen lightning damage a number of times. Sometimes it is mostly invisible. On one occasion it destroyed the 20 amp surge protector components in a metal box I built to protect a machine. The parts in the box disappeared with only black oily smudges and melted globules of metal left in the box. It also vaporized the breaker on that circuit in the main panel. Strangely, the $10 K machine survived.
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      • #4
        I'm not giving up that easy guys. I'd like to at least try to find a problem before junking it.

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        • #5
          You are wasting your time. The ICs on the board will be fried by overvoltage of only a few volts. 100,000 is more than enough to cook all of it. You mentioned a scorch mark on the board. It's totally fried. The "snap" was the fuse blowing again. The boards are multi layers, as many as six layers on some boards. They cannot be inspected or fixed if there is trace damage inside the board. The parts on nearly all new technology are unrepairable.
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          • #6
            I'm afraid I have to concur, and I am the obsessed "fixer", but even I know when I'm licked. That voltage spike could, and likely, took out 10+ solid state components that you have no clue, until you fix the first one, then the second one, then.......... It doesn't stop. I've managed to "repair" the power portion of lightning struck units only to face a myriad of other components that aren't functioning. It's like opening doors to a continuous maze that never ends. Sometimes you have to admit defeat. It's a tough decision, but trust me, it will whip you to your knees.
            Wayne

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            • #7
              The scorch mark was on a solder joint right by the power plug. The "snap" was not the fuse. The new one I put in is still good. Normally when I hear a "snap" I find a capacitor or something visibly damaged. That is not the case this time and has me stumped.

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              • #8
                Check the main switching transistors and diodes on the power supply. Replace any that act as 3 way shorts or 3 way open (for transistors/mosfets) in both directions.

                Replace any diodes that arnt diodes anymore.

                If that doesnt fix it, then yes damage has progressed past the PSU and is likey to be in unobtainable components and widespread and nearly impossable to find out where.

                Lightning is also basicly a worse case occurance, Lightning is millions of times more powerful then typical surges if it occured anywhere close.
                Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                • #9
                  I have found some evidence of life. I'm getting 3v now at the cable that goes from the power supply to the next board. This is an LCD tv, I've got no idea what voltage it should be running on....
                  If memory serves....the transistors are going to be the rectangle, three legged things on the heat sinks. Correct?

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                  • #10
                    Back in the 60's I repaired dozens of TV's struck by lightening.
                    Those old Tube sets would come back to life every time.
                    The tuners had an input balun (coil) in the Tuner that would fry, and sometimes the antenna lead-in would be vaporized.
                    I watched my neighbors outside antenna get hit. Next day I was over there making $5.
                    It was common practice to disconnect the TV's antenna during storms.
                    If your worried about a Solar Flair or a Electromagnetic Pulse (EMP), a battery powered Tube Radio is something to have squirreled away.
                    Tom M.

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                    • #11
                      As Evan suggested, many components these days won't handle much overvoltage. One of the main reasons I gave up electronics as a profession is the abundance of tiny surface mount chips you find on everything these days. In flat screen tvs, there are hundreds of them, and I did at one point try to change the bad ones to get the thing working again. Sometimes it worked out, but they would blow again. Maybe a minute later, maybe after a day of test running- there are so many things that interact on a modern circuit board that it's virtually useless wasting time trying to get one back up and running. Replace the board instead, and if that didn't fix it, replace another board. Then replace both boards at the same time because the fault on one blew the other one. Then replace both those boards, plus another one, because they all interact- then after losing 1500$ worth of boards, go buy a new tv for 400$.

                      Power supplies in modern equipment often have several mosfets in parallel in parts of the circuitry. You can check with an ohmeter and maybe find a short, but to narrow it down to one part, you have to start removing parts. Good luck with that, with the double sided boards and impossible access to individual parts-

                      I wish you well in your efforts to repair this, if you are that determined to try.
                      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                      • #12
                        Agree with the others. In my experience, lightning can do a lot of invisible damage, and it doesn't respect many of the rules that more civilized electrons do. I troubleshot a board once with lightning damage. It vaporized some traces and a transformer, but a small signal diode in the same circuit was still good. Farther downstream, about a quarter of the semiconductors were damaged, though they looked OK.
                        For just a little more, you can do it yourself!

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                        • #13
                          You can do as you like...... but lightning usually does visible and invisible damage.

                          The visible is "easy".... the invisible you can chase for days. And even when you "fix it" it may pop up a week later.

                          I have better things to do....... if it were a tube type, or even a discrete transistor type, I'd fix it too. But these lat screen and 3 huge IC tvs are not worth the effort....
                          1601

                          Keep eye on ball.
                          Hashim Khan

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                          • #14
                            No problem,
                            It will be the little red and blue thingy, next to the black and silver thingy
                            .

                            Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                            • #15
                              I give up. I now have power everywhere, but it still won't turn on. No display, not even a power light.

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