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Schottky Diode replacement question

Discussion in 'Electronic Repair' started by weiser1, Sep 25, 2005.

  1. weiser1

    weiser1 Guest

    Can I replace a BAT85 rated at 40V, 1Amp with a 1N5822 rated at 40V,
    3Amp?
    Are these like fuses if the amp rating is higher than the original
    specs, it burns up the cicuitry before it blows?
    Or will the diode blow at 40V?

    Thanks
     
  2. Arfa Daily

    Arfa Daily Guest

    It shouldn't burn up in the first place. A failed Schottky diode should blow
    a fuse, or if it's on the secondary side of a switch mode psu, normally
    cause the supply to go into cyclic shutdown.

    There should not be a problem substituting a 1N5822 for a BAT85 in terms of
    basic circuit operation. Both types will fail if more than 40v is placed
    across them in reverse. The BAT will fail if the following circuitry tries
    to draw more than 1A for too long, and the preceding circuitry lets it.
    Likewise, the 1N will fail if the following circuitry tries to draw more
    than 3A for any length of time, but as I said above, I would hope that
    whatever circuitry came before the diode, would not allow the circuitry that
    comes after, that amount of current via the diode.

    Arfa
     
  3. weiser1

    weiser1 Guest

    These diodes were in a GE corded/cordless phone hit by lightning. The
    rest of the phone operations still work fine, except when you plug in
    the phone line, it immediately says Line in use. It also blew a BZX
    27 (27V/1.3W Zener). I removed one lead of all the diodes (about 15)
    and found 4 BAT85 and 1 BZX27 tested shorted. With out a schematic, I
    would guess the surge on the line, took out the onhook and ring detect
    circuitry.
    Thanks for the reply Arfa
     
  4. Jim Adney

    Jim Adney Guest

    That should be fine, if there's room for it.
    Diodes are not generally sized to blow as fuses. They are sized to
    carry all the current and voltage that they should ever see under
    normal conditions.

    OTOH, if yours has blown, you might want to wonder why. This might
    just be a random failure, or a poorly choosen OE part, but it's more
    likely that something else is wrong downstream. You'll want to find
    that something else, and fix it, too.

    -
     
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