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CTC187 dead

Discussion in 'Electronic Repair' started by Mike Bates, Jan 30, 2006.

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  1. Mike Bates

    Mike Bates Guest

    I got this set, friend wants it fixed.

    He said the power button is messed up, and it doesnt turn on. well, I seen
    that it was a ctc187, I know thats not the case. I got the set, and pressed
    the button, it presses fine. I immidiately thought in my head, since I
    worked on these before, the 10uf cap in the SMPS primary is gone, fuse is
    gone, and STK is wasted. thats what I first thought.


    I took it apart, only to confirm my suspician, the fuse is wasted.


    I pulled it out, here is the rundown so far: caps look normal, no bloated or
    exploaded caps like on most of the ones I worked on.

    The fuse is gone, the HOT is shorted, and 1 of the 2 secondary diodes is
    shorted. The one that feeds the flyback and associated circuits is shorted.

    Ok, question. What caused the HOT to blow in the first place? flyback
    possibly bad?

    I got another board identical to it, that had a bad STK, and all the power
    supply caps. Everything was recapped, but the woman said she tossed it, and
    didnt want it fixed, so I never got the STK, and ended up robbing the caps
    and the NTSC processor for another set. The HOT and associated circuits are
    still OK.

    I wonder if I should just pull the flyback and HOT, with the diodes, and
    some blue pincussion caps and change them out?

    any thoughts would be appriciated.
     
  2. Guest

    Simple ring the flyback to find out if it is bad.
    Check the horizontal driver transformer solder connections, could also
    short HOT.
    Tuner ground problems or corrupted eeprom due to same can also blow
    HOT.
    Arcing back crt could also cause failure.
    Failure in the smps main b+ diode can blow the HOT.

    Lots of different possibilities, start doing the basic troubleshooting
    for that type of failure, then continue troubleshooting once unit can
    be powered up with the main b+ current limited.

    David
     
  3. Vince

    Vince Guest

    Make sure the diode that supplies the HOTr is good or bad, if its good the
    HOTr is bad , you have to unsolder one or the other, either one could cause
    the fuse to go.
    Vince
     
  4. Vince

    Vince Guest

    Hi!
    I have found that i can be either the diode that fernishes the power to the
    HOTr or the HOTr.unsolder to check, either one of these or the regulator can
    take out the fuse.
    Vince
     
  5. Mike Bates

    Mike Bates Guest

    the HOT is fine, I snipped the diode, and its indeed bad, and that means the
    STK is bad, and the 10uf cap in the primary caused it.


     
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