I think we can learn sometning from why the electric fence unit broke. (my recent post "Urgent ST FJ0916CI datasheet"):

The IC supply radial cased electrilytic cap has become loose because the rubber gasket had expanded and pulled the solder joint broken.  I guess then the PWM got crazy and destroyed the power FET.  The tracks of that is the IC, Power FET, and a resistor got blown.

The original failure reason i tink is that the cirquit board is covered with some grease, and it seems something in the grease diffuses into the gasket which then expands.

I have also found another radial eletrolytic cap on the cirquit board hich has also pushed itself out.

Lesson: Never use grease coating toghether with rubber part components!
(such as electrolytics)

I always use silicone coating.

The unit is twelve years old, but more than ten of them was on the shelf, so it served only one season.

/Morgan

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listserv@mitvma.mit.edu with SET PICList DIGEST in the body