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Fuse Blown After Transporting CRT Monitor

Discussion in 'Electronic Repair' started by [email protected], Feb 1, 2006.

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  1. Guest

    I have a Miro C2085 20" CRT monitor that was working until I gave it to
    my brother and he took it away. Now the fuse is blown within the power
    supply. When I replaced the fuse and turned on the monitor, the new
    fuse lit up instantly like a flash bulb as it also blew.

    There is definitely a short-circuit somewhere. The only way I can
    imagine that it came about was that monitor may have taken a hard
    bounce when my brother transported it in the back of his minivan. Yet I
    see no obvious damage to the surrounding external casing. Other than
    this, I have no explanation for why the monitor was once working but is
    no longer doing so.

    I don't remember what kind of CRT this was but the power supply board
    is a Sony part.

    Any and all advice will be welcomed.

    Thanks in advance.
     
  2. Gerard Bok

    Gerard Bok Guest

    Where does your brother keep his coins ?
    Any chance that your brother's premises are wired to a different
    voltage ?
     
  3. Guest

    My brother's house uses the same voltage as mine 120v. I'm in NewYork
    while he's in New Jersey but both are in the U.S. with the same line
    voltage.

    Anyway, he returned the monitor to me where I replaced the fuse only to
    see it blow again, so that's not at issue here.

    I did find a loose screw inside that I did remove. There was one
    missing for mounting the metal shielding just inside the plastic shell
    so that accounts for this. I had hoped that this would explain the
    short-circuit but I ended up blowing yet another fuse anyway.

    This monitor is much too large to be able to be shaken with ease so as
    to listen for any loose items rattling. I DID stand it up on different
    ends to see if this MIGHT happen but no. This thing is built pretty
    solid.

    BTW, the monitor uses a Sony Trinitron tube
     
  4. b

    b Guest

    if the unit was taken from a cold van into room temperature and
    switched on, condensation may have formed and shorted the power supply
    rectifier or HOT.
    you'll need to see the repair faq for trouleshoting this one:

    www.repairfaq.org.

    READ and observe the vital safety info as there are lethal voltages in
    these sets even after the plug has been pulled.
    -B.
     
  5. James Sweet

    James Sweet Guest


    The screw probably shorted something and blew a part in the power
    supply. If the fuse blows immediately I'd start by checking the rectifier.
     
  6. Guest

    It's quite possible this screw may have shorted something out within
    the power supply but I think that it is unlikely. The power supply has
    it's own metal cage and, when I disconnect all of the cables, can be
    completely removed from the monitor. Also, its PC board is positioned
    in a vertical orientation when mounted within the monitor while this is
    normally standing. The screw wasn't likely touching inside there. The
    scarier possibility is that it shorted out something near the flyback
    transformer.

    Now that I think about it, disconnecting the cables will isolate the
    power supply from the rest of the monitor. This should allow me to see
    if the power supply is still working properly by itself. Or at least
    not blow another fuse.

    What risk would I take for creating further damage to the monitor if I
    were to play with this?

    There are four connectors to the power supply. Five, if you include the
    AC power cord. Two are for ribbon cables which are most likely for
    low-voltage stuff such as logic chips. The other two are for heavier
    guage wiring obviously for high-voltage stuff. Of these, one is a
    two-pin connector while the other is a four-pin.

    One of these have to be for the monitor on/off switch. Which of these
    two? I'm not sure. My first guess would be the two-pin connector but
    the on/off switch could be a double-pole switch used to completely
    isolate the monitor electrically while turned off.
     
  7. b

    b Guest

    you need a load on the power supply . don't try to connect it without
    one or it'll probably die !
    replace any obviously shorted components, put it back in the set and
    power up with the 60w light bulb in place of the fuse as per the FAQ.
    Beyond this there's little you can do if you aren't expèrienced in
    this work. May be easier to get another monitor as there are planty of
    cheap used CRTS around these days for peanuts.
    -B
     
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