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RCA F27732SB TV Blows Fuse

Discussion in 'Electronic Repair' started by [email protected], Feb 11, 2008.

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  1. Guest

    Hi everyone,

    I have recently encountered a problem with my RCA 27" TV. The TV blows
    the fuse every time it is plugged in. I am unable to do voltage tests
    as there is NO power. I believe the problem is within the first few
    components (filter capacitor, diodes, chopper transistor, etc). I have
    not really taken a very good look at the set, but would like some sort
    of direction before I go ahead and start.

    Can someone direct me to the right direction of which are the most
    likely failed components?

    Thank you

    P.S. THE CHASSIS IS: CTC169CK5
     
  2. James Sweet

    James Sweet Guest


    Sounds like you pretty well nailed it. Check the chopper transistor and
    rectifier diodes on the input first, and keep in mind that if one of those
    checks bad, other parts in the area may be bad as well.
     
  3. Guest

    I have tested the 4 rectifier diodes and they all seem to be opened
    (VOLTAGE DROP IN BOTH DIRECTIONS). Do you thing that these shorted
    diodes could have shorted the IC regulator and the chopper transistor?
    Thanks
     
  4. b

    b Guest

    replace the diodes, remove the chopper transistor AND the PTC, and
    power the set up with 100w bulb in series int he mains line. be wary
    if it glows brightly. if it is dim or fades, you will know your
    rectifier is probably ok now.
    -B
     
  5. James Sweet

    James Sweet Guest

    Are the diodes shorted or are they open? Did you test them out of circuit?
     
  6. Guest

    I believe the diodes are shorted as the voltage drop appears in both
    directions. I tested them in the circuit. Do I get false readings if
    they are in the circuit? Thanks.
     
  7. Do I get false readings if
    Very often - depends on the other components in the circuit. Only way to
    know for sure is to test them out of circuit.

    Mark Z.
     
  8. Meat Plow

    Meat Plow Guest

    Unsolder one leg of each device and retest using your meter's diode check
    function. Often, in circuit tests can deceive.
     
  9. Guest

    In or out of circuit, bridges, if not short usually good, also take a
    look at the output transistor next to the flyback on a heatsink, and
    cold solders on the horiz. drive transformer. also older rca's have a
    lot of bizarre problems due to their "on board" tuner, if you do
    manage to get it on just go over the tuner to avoid future problems.
    Shane.
     
  10. Guest

    Thanks
    I will retest the diodes and I will try to replace them. I will also
    test the chopper transistor along with HOT.
    Also I have found 1 other diode shorted right near the chopper
    transformer. Hmmmmm
     
  11. Meat Plow

    Meat Plow Guest

    Consider yourself lucky it's not one of the older RCA sets that used two
    SCR's to derive flyback scan.
     
  12. Guest

    Hi
    I will try to test some HV components to determine how bad the short
    really is and I will post again.
     
  13. Guest

    Hi again,
    I was wondering, what could have caused all 4 rectifier diodes to
    short?
     
  14. Meat Plow

    Meat Plow Guest

    What else have you found wrong? Is the set working now?
     
  15. Guest

    Hi
    I am still working on the set. I have not gotten around to check it
    out. At the moment I have removed all 4 rectifiers. I will test the
    HOT and chopper today.
     
  16. b

    b Guest

    could be several things - mains surge, bad ptc, bad chopper, shorted
    mains capacitor... being common reasons in my experience. usually,
    however, a fusible resistor opens first in the case of problems
    further into the power supply .
    -b
     
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