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Deawoo 28" crt

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    #1

    Deawoo 28" crt

    Got a phone call from my dad last night saying his TV has packed in, when he turned it on it made a loud crackle n pop then went off and smelt funny,

    popped down to have a look and all i could find was one 1000uf 35v cap that has some how broken loose of its tracks that its soldered to!!!! not a dry joint as the solder is still connected the the legs but its taken the track off the pcb

    nothing else looks damaged, just this one cap that is loose/ not connected, stuck the mutlimeter on 200M ohms and its very slow to start building up resistance after being shorted shorted, other caps i'v done this to are quite quick.

    anyone else known caps to brake loose like this?

    Regs
    Rich
    Tags: None
    #2
    Re: Deawoo 28" crt

    little update, the cap in question isn't a problem and must of always been like this,

    started looking on the 240v input side as the fuse had gone, using the dmm i found that the resistance on the supply is about 100ohm?

    found the switching transistor is fried also a resistor that goes to pin 2 (source)

    whats the chances of just the Off-line Quasi-resonant Flyback Switching Regulator and the resistor being the only problem?
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      #3
      Re: Deawoo 28" crt

      It could very well have died of old age (inadequate heatsinking), but when you replace it do insert a light bulb in series with the mains. Use a 60W unit for minimal damage, should be enough for the power supply to go into standby mode. If the bulb stays lit full brightness you still have something shorted.

      Also check the horizontal output transistor and B+ supply.
      Originally posted by PeteS in CA
      Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
      A working TV? How boring!

      Comment

        #4
        Re: Deawoo 28" crt

        Originally posted by Th3_uN1Qu3 View Post
        It could very well have died of old age (inadequate heatsinking), but when you replace it do insert a light bulb in series with the mains. Use a 60W unit for minimal damage, should be enough for the power supply to go into standby mode. If the bulb stays lit full brightness you still have something shorted.

        Also check the horizontal output transistor and B+ supply.
        It's 8yo so probably age, good idea with the bulb, using a dmm I found it shows a short over live and neutral supply but only if the degaussing coil is plugged onto the board, traced this to a 3 pin little block that has resistance between it's live and neutral input but a short between live and coil output (coil return goes back to neutral) couldn't find much on degaussing circuit on net! Is this normal? I read that the little block could be a thermister to trigger the degaus when the tv is turned on and resets once power has been off long enough, guess the resistor gives off heat to keep it turned off, or I could be completely wrong lol

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          #5
          Re: Deawoo 28" crt

          Originally posted by Mr_Bodgit View Post
          Itraced this to a 3 pin little block that has resistance between it's live and neutral input but a short between live and coil output (coil return goes back to neutral) couldn't find much on degaussing circuit on net! Is this normal?
          Yes it's normal. That is the PTC thermistor. It goes high resistance once it heats up, and it stays that way. But since it is a part that runs hot all the time, it could have died. They usually fail open though so yours is probably good.
          Originally posted by PeteS in CA
          Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
          A working TV? How boring!

          Comment

            #6
            Re: Deawoo 28" crt

            sounds like the fly arced.look it over.hot probably went and took the reg with it.

            Comment

              #7
              Re: Deawoo 28" crt

              Cheers Tu, thought I'd worked it out correctly,

              Kc, will look at the reg,

              got to find a supplier for the fly lol google just throws up data sheets

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