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Pre-Burn Assembly Instructions
Before the boards are shipped out, they are placed in an oven at an
elevated temperature to stress the electronics and artificially age them.
The theory is that this weeds out boards that would've likely failed in the
test machine, perhaps one or two years down the road. Instead they fail in
the lab and everybody has less to worry about in the long run.
To prepare a board for burn-in, remove the clock and any other jumpers
besides the standard clock and LED jumpers, construct a support sheet, and
place it in the for-burn section of the particle board rack.
Constructing a support sheet:
- Obtain a metal sheet of the right dimensions for the board you want to
fit on it from the wood crates under the shelves filled with components.
- There are pre-drilled holes on the test board for the support
screws, which are matched by a set of holes on the support sheet. Fill
in the screw holes with screws from bin #7 and nuts from bin #9. Don't
forget to fill in the holes below the mezz card. There is actually some art to tightening these screws, so here goes:
- You can hand-tighten the nuts and then use the socket wrench to
further
tighten them. Beware that if your hands are not weak, it's easy to
overtighten the nuts and start to strip the screw. That's obviously a
problem. An easier way is:
- Tighten the screws using the electric screwdriver. Remember that you
have to hold it parallel to the screw's axis for the driver head to not
strip the screw as it tightens and don't be afraid to give it some
pressure. Until the nut makes contact with the board (and friction between
them holds it in one place) use your finger to keep the nut from rotating.
The electric screwdriver has a built-in torque limiter that's set to the
lowest point, and is just right for this purpose. The screwdriver will make
clicking sounds when it can't tighten the screw anymore.
- If your hands are strong enough, it's not out of the question to hand
tighten the nuts by turning them yourself, using the socket to give you
some leverage.
- When the screws are in, take a cloth or your hand or something and
wipe the front and back of the board clean. As the screws tighten, small
metal shavings pile up which may at some point come into contact with the
board and cause an impossible-to-find short.
- Lay the board on the mounting screws and gently add a second nut on
the corner screws. The reason they're only put on the corner is because it
will very probably be necessary to take the board off the support sheet for
the second round of tests.
Place the board into the to-burn stack in the particle board rack. The
exact place for this tends to vary, so ask around.
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Matt Matolcsi (madhat@ucla.edu); Last revision: 2003/07/17