"Tom Gardner" Mars@Tacks wrote in message
...
I got me Pro-Face PLC back from the manufacturer today. I had posted about
the failure a few weeks ago. It turns out that there was some sort of
corrosion on the main board and the video board. The PLC is in a gasketed
enclosure with three Greenfield cables coming in. The machine or the
control box never got wet and there is nothing in the air. The heat goes
from 65 day to 55 night with overhead gas furnaces.
Could just the Greenfield be letting moisture in? How do I prevent it
from happening again? A light bulb running all the time? A vent fan?
Maybe the thing shouldn't be that well sealed?

Here are some pix of the PLC, and enclosure.

http://i954.photobucket.com/albums/a...pse545a784.jpg

http://i954.photobucket.com/albums/a...psb1238b22.jpg

http://i954.photobucket.com/albums/a...pscbe73616.jpg




Something corrosive is outgasing and being trapped in your tightly closed
box. When PVC breaks down it can outgas HCl. Some silicones outgas acetic
acid. Other plastics can outgas formic acid or formaldehyde.