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Discussion in 'Electronic Repair' started by onyxx, Oct 19, 2005.

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  1. onyxx

    onyxx Guest

    Hi, here is the thing...

    with the HOT removed and power on, I measure 0V(this is not good
    right?)at both B and E (remember, HOT removed)and 113V at C (this is a
    15 inch color monitor so 113V B+ seems proper)When I connect the HOT
    back on, I measure 0V at B and E and OVER a THOUSAND VOLTS at C!!!!!!
    I have the monitor connected with a 150W light Bulb in series, I can
    hear the click click click of the PS trying to start but that is
    it...nothig else.
    I´ve measure the HOT (C4769) with my DMM and i get what it seems to be
    a short, but looking at the diagram from the transistor´s datasheet, I
    see other components in there that might indicate that the 50 Ohm
    reading i get, is correct.
    Can anyone point me in the right direction here?

  2. Guest

    Me thinks you are way over your head here.... you should go to the
    website for this newsgroup at
    there, with some searching, you will find a wealth of troubleshooting
    tips, component testing methods, repair proceedures and IMPORTANT
    SAFETY information that will keep you alive while you are poking around
    inside your very dangerous television.
    Your test results with the HOT removed are completely NORMAL... no
    voltage on the B and E terminals where the HOT was installed and B+ on
    the C terminal that goes to the primary of the flyback which the other
    end is connected to the regulated B+ in the power supply.... HOWEVER,
    the reading of 113 volts seems low..... maybe it should be a little
    higher, maybe like 125 to 145 volts depending on the design of the
    television. You should not attempt to measure the C terminal voltage
    when the HOT is in the circuit and the television is turned on.... the
    very high voltage you are reading is due to the back emf of the flyback
    windings getting fast switched by the HOT... and can easily damage your
    meter... It also sounds like your HOT may be faulty... test again
    and go to the repairfaq and learn more before proceeding.
    ========== ============= ===========
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