On Thu, 24 Jan 2013 00:14:14 -0500, Tom Gardner Mars@Tacks wrote:

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


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Hey Tom,

We had a multi-lane bi-directional stepper switch ( 18P25T ) in a salt
plant, that would corrode to un-usability every six months, and the
switch and our labour to replace it was considerable. It sat in a
closed but not sealed cabinet, and there was no direct heat in the
machine room, so the temperature varied quite a bit by season. I put
a Plexiglas window in the swing lid of 12" X 12" X9" deep gasketed
cabinet and a 60 watt "Rough Service" light bulb with a simple light
dimmer to make the bulb just glow at about 25 watts. Took twice as
long to do this the one time, including installing, moving, re-wiring,
and caulking the wire-cable so the box was essentially air-tight. In
the 9 more years that I was still in the trade, the switch stepped
without failure, and used the same light bulb.

Worked for me.

Brian Lawson