15 Aug
2012
15 Aug
'12
11:09 a.m.
Message: 2
Date: Tue, 14 Aug 2012 11:20:58 -0700
From: Earl Evans <earl at retrobits.com>
To: "General Discussion: On-Topic Posts Only" <cctech at classiccmp.org>
Subject: PDPs in the garage
Message-ID:
<CAMDAk4d3sfqET1Rj3Yw45ctgg+2BLHr=aSvyVqBxnGurveNhHA at mail.gmail.com>
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Hi folks,
I'm a little concerned about the load that my PDP-11 cabinet (rack mount,
dual RL02 drives) is putting on the floor in my daylight basement. Also,
I'm thinking that recovering the space might be nice, so I was considering
moving the PDP-11 system back to the garage.
If any of you have a PDP or other big-iron systems in the garage, how do
you deal with temperature extremes (hot in summer, cold in winter)? Do you
simply not operate the computer when it's too hot or cold? Do you think
it's a risk to even store the system in the garage?
My location is Portland, Oregon, so it doesn't really get super cold in the
winter. I think the coldest I've measured in the garage is 50F. But
summer can get pretty warm. It's scheduled to get 85F today, and we had
100F a week or two ago. Of course the garage doesn't get as hot as outside
temps, but it can get up there.
I realize heat can be a big enemy of computers/electronics. Also, since
the RL02 drives are mechanical and precision devices, they might not take
well to temperature shifts.
Thoughts?
- Earl
I could tell you a story about an 11/780 at Fort Monmouth that ran
without air conditioning and with the windows upen for 3 months.
Serious intermittant problems sprung up. The humidity had rust on the
TU45 tape drive motors.
The problem isn't heat -- it's the rate of change. You get serious
expansion cracks in the boards when the etches expand and contract.
The faster the rate of change in temporature when running (both up and
down) the worse the issue.
The machine was flaky as hell. The thing would crash VAX/VMS about 5
times daily.
I actually would boot the machine and hit each one with my little
brass hammer. If it crashed... the board was replaced. Swapped
about 6 boards in the data path and cache sections and the box was
then stable for over three years.
The 11/34's a lot lower in power draw and slower. It's probably less
sensitive with some larger etches.
I'd worry more about the peripherals. Disk drives with rusty parts in
them are probably a bad thing.
I know the tape drives would have a problem. The RL02's might even
have a different flying height depending upon the temperature which
could end in head crashes.
If you kept the internal temp under 100 degrees you're probably ok...
but if the outside temp's above 100...
The real trick is to keep the temp as steady as possible. Perhaps
strategic fan placement to keep it from getting too hot in certain
places.
Bill
--
d|i|g|i|t|a|l had it THEN. Don't you wish you could still buy it now!
pechter-at-gmail.com