On Thu, 17 Jul 2008 02:35:44 -0700 (PDT), Myauk
put finger to keyboard and composed:

Actually, it is just a 4093 IC using all four gates inside it, with
resistors and capacitors mounted around it. It is easy to replace the
gates if they are faulty.

I have some experience in power supplies and PWM circuits but trying
to repair the alram cards is new experience.
This is my first time trying to repair the alarm cards.

I have repaired one alarm with a faulty CMOS gate. That's the limit of
my experience. :-)

Coincidentally, my faulty part was also a 4093:
http://groups.google.com/group/aus.e...4?dmode=source

Can I assume that it happened because of the faulty gates?
I will try replacing the gates today.

I would think that CMOS inputs would be more prone to damage because
they are connected to the outside world.

Can anybody suggest me some idea for testing such SR NAND latch
circuits?

Best Regards

Your testing method seems fine to me, ie apply all combinations of 1s
and 0s to the inputs and test for the correct outputs.

- Franc Zabkar
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