Contents
There is heavy equipment in the lab, and some of the materials we will
work with pose hazards. Therefore:
- WEAR CLOSED-TOE SHOES whenever lifting anything that could fall, and
whenever working with solder, potentially hazardous chemicals, or power tools.
- WEAR SAFETY GLASSES whenever working with tools or potentially hazardous
chemicals.
- AVOID LOOSE CLOTHING when working around any machinery containing
exposed moving parts -- this applies to power tools in general, and also
the paper tape transport, the Teletype (with its cover open), and the
ventilating fans inside the computer.
- SECURE LONG HAIR when working around any machinery containing moving
parts -- for the same reasons given above.
- STOP TO THINK before doing anything you have never done before.
Ask, is this safe? What risks does this pose? How can the risks be minimized?
- DO NOT USE TOOLS that you are unfamiliar with except under the supervision
of someone who knows their proper use.
The rack holding the computer weighs 225 pounds. The computer itself
(including the power supply) weighs 250 pounds. When the computer is
extended from the rack to the limit of its rack slides, it is dangerously
close to being unbalanced. The risk is greatest when the weight of the rack
is carried on the wheeled casters and the casters are pivoted toward
the rear. Therefore:
- NEVER WORK ALONE when the computer is extended from the rack.
Someone should be there to call for help if you drop a 500 pound computer
on yourself.
- NEVER EXTEND THE COMPUTER FROM THE RACK without lowering the front
leveling feet on the rack so they rest on the floor.
All of the rack-mounted equipment can be removed from the relay racks,
but some of it is heavy, fragile or both. Furthermore, careless work
poses risks not only to the piece of equipment being mounted or dismounted,
but to the adjacent equipment. Therefore:
- NEVER WORK ALONE when removing or installing equipment from the
mounting racks. At least one person should support the equipment while
another person loosens or tightens the mounting screws. (This does not
apply to individual circuit boards or cables.)
- PLAN AHEAD! Before moving anything heavy or delicate, make sure you
are adequately prepared to hold its weight, make sure that
you know where you will put it and make sure you have a safe clear path from
where it is to where you will put it.
This computer contains power supplies with outputs of up to 40 volts,
and the majority of the logic operates between a +10 volt bus and a -15
volt bus. These are hazardous voltages that are significantly higher
than the voltages used in modern logic. Furthermore, the 110-volt
power on the input side of the power supply is exposed on terminal
strips inside the machine. A current of 20 milliamps (0.02 Amps) can
kill a person. The capacitors in our computer's main 15 volt power supply
store 47.25 Joules (of energy), comparable to the amount of energy in the
most powerful air guns, or the energy in a 1 kilogram weight dropped
from 4.82 meters, or a 1 pound weight dropped from 34.87 feet.
- NEVER WORK ALONE if any part of the cabinet is open when the machine
is plugged in or has been plugged in within the last few minutes.
If you shock yourself, you want someone on hand to help.
- LEARN BASIC ELECTRICAL SAFETY. This video is a good intro,
despite its industrial emphasis and annoying "preview" graphic:
--
https://www.youtube.com/watch?v=IwI73x0ZLOs.
- LEARN CPR. You may never need this skill, but when it is needed,
it can save someone's life. This is a good half-hour first-aid video:
--
https://www.youtube.com/watch?v=9ttt4mO3cYk.
- WORK WITH DRY HANDS. Wet or sweaty skin is roughly 100 times more
conductive than dry skin. The hand dryer in the bathroom is feeble, so
either wait or towel dry your hands for an additional safety margin after
using it.
- UNPLUG OR TURN OFF everything before you leave the room, except
where there is a specific need to leave something turned on (for example,
a battery charger).
- UNPLUG OR TURN OFF equipment and let it sit a few minutes before you
make any changes to cabling or before you install or remove circuit boards.
(USB cables can be plugged and unplugged while machinery is turned on,
but antique computer equipment was rarely designed to allow this.)
- BEWARE OF ELECTRICAL CORDS. The retrocomputing lab has plenty of
electrical outlets. Always use the outlet closest to where you are
working. Avoid routing cords across an aisle where people might walk, if
at all possible.
This machine was built using tin-lead solder, and some of the chemicals we
will use in cleaning and restoring the machines pose potential hazards.
- WASH YOUR HANDS before you eat or drink anything after you come
in contact with solder or toxic chemicals. There is a bathroom around
the corner from the retrocomputing lab. Use it.
- WEAR GLOVES when working with paint, glue or solvents.
- TAKE IT OUTSIDE before using degreasing agents or solvent-based glues.
OK, a small spritz of WD40 is OK in the lab, as is a dab of glue,
but for large-scale use, ventilation matters.
Circuit boards and power supply wiring on this machine were assembled using
tin-lead solder. We will have to connect and disconnect a small number of
solder joints during the refurbishment of the power supplies, and it is highly
likely that we will have to repair some circuit boards. Lead is toxic and
the melting point of tin-lead solder is over 360°F or 180°C, hot
enough to cause severe burns. Therefore:
- DO NOT SOLDER unless you have proper training or you are closely
supervised by someone who has the training.
- UNPLUG ALL SOLDERING TOOLS AND VERIFY THAT THEY ARE COLD before you
leave.
- WASH YOUR HANDS after soldering, regardless of whether you believe you
came in contact with any solder.
- CLEAN UP YOUR WORK AREA after soldering. Small splatters of solder
should be swept up and discarded properly.
The PDP-8 computer in the retrocomputing lab is one of only a handful of
surving rack-mounted PDP-8 systems. We do not know of any surviving PDP-8
systems that include an A-D converter. Beside the value of the system itself,
the test instruments and tools we will be using in the lab have value.
Therefore:
- LOCK THE DOOR before you leave. Leaving to wash your hands is OK,
but the last one out of the lab should make sure the door is locked before
leaving the building.
- TRY THE KNOB to be sure you locked the door. The lock on the
Retrocomputing Lab provides very little feedback to tell you whether you
actually did anything by turning the key.
- RETURN YOUR KEY when you are done with it.
- DO NOT LOAN LAB KEYS.
- ASK BEFORE BRINGING GUESTS into the lab.
- GUESTS MUST SIGN IN in the log book.
- GUESTS MUST REVIEW THESE RULES before they act as a second
person for the "never work alone" rules.
- DO NOT REMOVE ANYTHING FROM THE LAB without logging the transaction in
the log book. Record your name, contact information, the reason for the
removal, and the intended return time.
- DO NOT LEAVE TOOLS IN THE LAB unless you intend that they be
available for the use of others working in the lab.
- DO NOT REMOVE OTHER PEOPLE'S PROPERTY from the lab.
- LABEL ALL PERSONAL PROPERTY left in the lab. Labels must be
prominent, easy to read, and difficult to accidently remove.
There is a log book in the lab so that we can track both the status of
the project and maintain lab security.
- LOG YOUR WORK. Nothing should be done without leaving a record of
who did it and what was accomplished (or not accomplished, as the case may
be). Before you leave the lab, write a very very brief description in the
log book that identifies the date, who you are, what part you worked on,
and the condition you left it in. Before the day is over
(or, in the worst case, the next morning) E-mail any photos and more
detail to jones@cs.uiowa.edu for inclusion in the on-line log.
- REVIEW THE LOG before working on anything. Check to see what was
done since you were last in the lab.
- DO NOT REMOVE THE LOG BOOK from the lab.
Our goal is to restore things to working condition. If we lose or misplace
parts, this will be difficult. Therefore:
- LABEL THE PARTS after you disassemble anything. We will keep a stock
of luggage tags and envelopes on hand so you can do this easily.
- PUT SCREWS BACK IN THEIR HOLES after you unscrew them to dismount
a part. This is the best way to keep track of what screw went where. Failure
to do this tends to lead to large numbers of loose screws and no idea which
screw went where when the time comes to reassemble something.
- TAKE PHOTOS to document the steps in disassembling anything, so you can
follow those steps in reverse to reassemble it.
- DO NOT REMOVE ANYTHING FROM THE LAB without logging the transaction in
the log book. Record your name, contact information, the reason for the
removal, and the intended return time.
The University has long ago cut back on custodial support, and
some parts of old computers, most notably the foam used in cabinet gaskets,
sheds considerable dust when disturbed.
Therefore:
- CLEAN THINGS UP. We have provided a broom, dust pan and trash can.
If you make a mess, sweep it up, if you are annoyed by crud on the floor,
sweep it up.
- EMPTY THE TRASH CAN if it fills. Don't rely on cusodial services for
this. There are larger trash cans in the hallway that are routinely emptied
by the custodial staff.
- THE TRASH CAN IS NOT FOR RECYCLABLE PAPER. There are big recycling bins
out in the hall. Use them for paper.
