Reset Retry on Sun Xylogics Controller - Revisited

[Brian Kantor]

A few weeks ago, I posted a message asking for help with this problem.
Thank you to all who responded with helpful advice (there were many of
you).

What I finally found the problem to be is one of cooling.  In our
configuration, the SUN 170/FS is mounted in a rack with an Eagle disk,
an Archive cartridge tape, and some other equipment that isn't running
yet.

What appears happens is this:  the eagle draws in room air through its
front panel, cools itself (and warms the air) and blows it out the back
of the eagle.  Right above the eagle is the air intake for the SUN
170/FS.  So the hot air from the eagle gets used to 'cool' the boards in
the sun.  Combine this with the fact that there was another card 
in the sun right next to the xylogics, and with the low velocity fans
that Sun uses in the 170/FS, and you have a severe heat problem.  In
fact, I burned my fingers on one of the PALs on the Xylogics board.

What I did to cure it:  I put a sheet of cardboard under the sun,
covering as little of the screen as possible, whilst deflecting the air
coming out of the Eagle away from the screen where air is sucked into
the sun.  I replaced the two wimpy fans in the 170/FS with a couple of
high-velocity units from our local electronics junk store.  I moved the
xylogics board over one slot so that there was a blank slot on the
component side of the controller to improve air flow.  I put a cardboard
baffle on the side of the cardcage (next to the power supply) so that
air doesn't spill out into the rest of the 170/FS cabinet until its
passed over the cards.  I put gaffer's tape (like duct tape, but doesn't
get slimy) over the bottom of the card cage covering unused slots so
that air had to travel up through the cards.  And finally, I moved the
Archive drive up one racknotch, so that the screen holes on the top of
the 170/FS had about an inch of clearance to let air out.

Things are running a whole lot cooler inside now - cards only feel warm
to the touch, not hot.  And I haven't seen the problem at all in the
last two weeks.

An awful lot of electronic equipment is undercooled.  I've added fans to
the top of our racal-vadic modem racks and cut the failure rate way
down, put fans on terminals, printers, tape drives, and whatever was
running hotter than I can touch comfortably.

Sure it makes more noise.  But this room has a vax 780 and 750, a couple
of eagle drives, an RM03, and a bunch of CDC disks.  Not to mention the
air conditioner blowers.  Next to that, a few more fans in the sun aren't
noticed.  (I think a 780 sounds like a Boeing 747 trying to hover - but 
at least its cool inside!)

	from the land of cool breezes...

	Brian Kantor	UC San Diego
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