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weiser1
 
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Default Schottky Diode replacement question


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

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Arfa Daily
 
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"weiser1" wrote in message
...

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

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


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weiser1
 
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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



On Sun, 25 Sep 2005 16:24:09 GMT, "Arfa Daily"
wrote:


"weiser1" wrote in message
.. .

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

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


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Jim Adney
 
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On Sun, 25 Sep 2005 04:15:10 GMT weiser1 wrote:

Can I replace a BAT85 rated at 40V, 1Amp with a 1N5822 rated at 40V,
3Amp?


That should be fine, if there's room for it.

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?


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.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------
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