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[email protected][_2_] captainvideo462002@yahoo.com[_2_] is offline
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Default Surface mount diode identification

On Sep 2, 5:19*am, Ross Herbert wrote:
On Mon, 31 Aug 2009 05:18:42 -0700 (PDT), wrote:

:On Aug 30, 3:28*am, Ross Herbert wrote:
: On Sat, 29 Aug 2009 11:53:54 -0700 (PDT), "
:: wrote:

:
: :I have an alarm board with two shorted surface mount diodes. These are
: :about the size of a quarter watt carbon resistor only just a slight
: :bit fatter. They are marked: MX6AA and MX50AA. Can anyone please
: :identify these for me? Thanks, Lenny.
:
: Are they glass MELF style or moulded plastic similar to either of these
photos?http://img.alibaba.com/photo/1078070...LL4007.jpghttp...
:
: My first guess would be 1W zeners so perhaps you can check to see if they
have
: 6V and 50V ratings respectively (assuming they are not dead).
:They are not round more like flat and they are definitly shorted.
:Lenny

'Fraid you are stuffed then.. Other than figuring out the function by tracing
out the circuit around those devices and then making some intelligent
deductions...

No manufacturer ident (on the board or the system) you can approach?


The board is a fire alarm main board and is manufactured by GE
Security probably off shore. These diodes could be anyones I guess.
The thing is, this exact failure, that is these two diodes shorting
out has happened many times before on this security installation. It
usually occurrs after a bad lightning storm. For the time being GE has
repaired these units under warranty but the warranty period is coming
to an end. These boards are no longer in production so it also
involves sending the board out for repair and so the premises are not
protected during that period. I would have to guess that at least one
of these diodes is accross the input reversed biased to ground because
when it shorts out the unit displays "Ground fault" and the zone is
knocked out of commission. Would you think that this is probably a
zener or perhaps just a standard run of the mill diode? Lenny