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No power, no led light. Rear projection tv

Discussion in 'Power Electronics' started by Echo26, Jan 19, 2021.

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  1. Echo26

    Echo26

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    Jan 19, 2021
    Badly needed help and had been troubleshooting for 4days. I have a Sony Kpf43m91 rear projection tv, i gues was built jn 2007 . Everything's fine until we heard a hiss and a pop on it, opened and saw a 22uf cap blown. I replaced it with a new one, still no power or led light response. Cant even get into service mode. I have the service manual and schematic , found no voltages on standby and low voltage on the relay line. Primary Power supply is active and properly supplies 240v.
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Fuses?
     
  3. Echo26

    Echo26

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    Jan 19, 2021
    No blown fuses. Had it checked first, i thought the same thing. But its actually fine. Cord was fine. Primary powersupply is active.
     
  4. shrtrnd

    shrtrnd

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    Jan 15, 2010
    Trace connections to your blown cap. You probably lost a semiconductor and saw a current surge through that cap.
     
  5. Echo26

    Echo26

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    Jan 19, 2021
    I'll chekc it out . Does it really affect the secondary power supply? The blown cap was around the horizontal section.
     
  6. shrtrnd

    shrtrnd

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    Jan 15, 2010
    Let me think.
    Your fuses are OK (I hope you found all of them).
    You heard a hiss and a pop, and found a blown 22ufd cap, which you replaced.
    But you still have no power and no LED light.
    Yes, it would seem to me that something else in the 22ufd cap circuit is not quite right.
    I would be looking for a component that allowed smoke to escape from your 22ufd cap, burned 'open-circuit' now, and is therefore denying voltage to the affected circuit.
    Good luck.
     
    Last edited: Jan 21, 2021
  7. Echo26

    Echo26

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    Jan 19, 2021
    Seems
    yeah I mean, I know a bit on voltage acheckin and trouble shooting but that cap is too far from the h.out of the yoke, and the primary and secondary supply was on the second board. I'll have to check it out again. These TV's are so complicated not just like regular Crt tvs. I'm still waiting for my new multi tester, i have blown my old one.
     
  8. shrtrnd

    shrtrnd

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    Jan 15, 2010
    Be careful in there. Not worth a trip the the hospital if you're unfamiliar with this circuit.
     
    Martaine2005 likes this.
  9. Echo26

    Echo26

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    Jan 19, 2021
    Yeah, i remember putting always one hand on the pocket. Seeing a 30kv dc in a schematic is mundane.
     
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