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Sharp TV - Blue Screen - Blows HOT

Discussion in 'Electronic Repair' started by Arnold Stewart, Dec 4, 2005.

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  1. Sharp TV Model(Chassis) CJ27D30 Manufactured July 1997
    TV came into the shop with a blown fuse and shorted HOT. After doing
    some tests, and some soldering, I decided to replace the HOT & fuse. TV
    worked fine for three days. Then suddenly, on day four, after being on
    for about a half hour, the TV lost picture & sound. A blue screen
    appeared, then faded to white. I tried connecting A/V connections. No
    change. Then the HOT shorted and blew the fuse.
    Before doing anything more with the set I thought that maybe somebody on
    this group may have experienced this problem before and could share his
    knowledge, which could save me a lot of time.
     
  2. Guest

    Sharp bought a bunch of Zenith picture tubes around that time. I have
    seen the Zenith made shorting picture tubes in Sharp 25" sets do the
    exact symptom you described. Possibly the 27" tube is shorting,
    causing excessive current, and blowing the HOT.
     
  3. Guest

    I think maybe you have used a sub standard part... please to convince
    the master why i shouldnt think this...?
     
  4. The only thing that I changed was the HOT and the fuse. The fuse is
    certainly not the cause. Before changing the HOT I got a data sheet. I
    replaced it with an exact same part with the same specifications.
    However I don't think the HOT is the cause of the problem. I think that
    the picture tube is shorting causing the blue raster, then putting a
    load on the HOT causing it to fail. I've isolated the filament pins on
    the tube circuit board and used Mr. Goldwasser's trick of having a
    floating cathode circuit (wrap a wire around HV transfo ferrite). If the
    short is to the cathode then the TV is fixed. Has been running now for
    three days.
    (If the master is not convinced about substandard part being used, can
    he explain?)
     
  5. Art

    Art Guest

    Disconnect the crt board and see if again it draws enough current to blow
    another horiz output.then ring the LOPT.
     
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