On Wed, 19 Mar 2014 14:19:19 -0500, Jon Elson
wrote:

wrote:

Thanks so far Cydrome, Matt, and Jon for reading and replying with
suggestions for finding the board problem. Last night I identified
every device on the board and made a list.

OK, not an opto anywhere, so my idea is toast! So, is it clear that
powering off doesn't fix it, but reseating the board DOES, at least
temporarily? If so, that pretty much indicates a connection problem.
Most of this stuff was wave soldered, so it is not real likely there
are bad solder joints on the chip-board connection. What type of
connectors are on the board-backplane connection? If Elco Vari-lock
or similar contact, they need to be squeezed. My old Allen-Bradley 7320
control was all Elco Vari-Lock contacts without the plastic housings
on the board contacts. This allows them to get bent apart when the board
is wiggled out. Elco vari-Lock contacts are hermaphroditic, and sort of
a narrow fork. The close faces of the tines are angled, and wipe against
the other contact, assuming the tines are parallel.

So, I have no idea whether your control uses this type contact, but I
definitely ran into this on that old A-B. Card edge contacts can get dirty
or sprung after many insert/remove cycles.

Jon
It seems like there is a heat problem and some sort of removal and
replace problem too. When the machine is run with the cabinet closed
it alarms out faster than when it is run with the cabinet open. I have
been so busy running the machine and working around this problem that
I may be wrong about removing and replacing. Today I'm a little less
busy and I'm going to try a couple experiments.
Eric

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