On Wed, 2 Sep 2009 23:21:30 -0700 (PDT), wrote:

: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
ut 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
rotected during that period. I would have to guess that at least one
f 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

I doubt it is a standard diode. More like a zener or transorb.
Did you try the GESecurity website? I notice that if you have a login and
password you can get access to the reference manual for some of their FA
systems, eg. Fireworx;
http://www.gesecurity.com/portal/sit...true&seriesID=