How to revive a PDP-8e/f/m
- STOP! Do not re-insert any removed card. Don't
take out any cards with the idea of "looking at them" and then putting
them back in. If you have already removed some, leave them out.
- Remove the lid. Scrape the crumbly foam into the
trash. Use De-solve-it or other solvent to gooify the adhesive
that is left and scrape it off with a plastic scraper. Get it all
off, clean the lid thoroughly. You must not leave any bits,
especially stick bits that will fall back into the backplane.
- Vacuum out the box, the top of the cards and any open
- Write down the card numbers and locations, remove the cards
and store safely. Note the locations and orientations of those
little top connector blocks. Note the colors of the wires and
where they go. Core memory is in sets, do not interchange
identically-numbered cards between sets.
- Vacuum out the crumbly bits from the backplane and the rest
of the chassis. Dust the insides out, get all the bits.
- Undo the 2 hex head screws holding the knob on,
remove. Remove the 4 bezel screws, remove the bezel and front
cover. Undo the two screws holding the front panel in, remove the
wire(s), unplug it.
- Undo the power harness to the backplane, remove the hex
screws holding the backplane(s) down and remove them, remove the
- Pick up the foam pad under from the underside of the
backplane (it shouldn't be glued down), discard and vacuum again.
Get all the bits out.
- Use dried, compress air to blow any remaining debris out of
the backplane. You want it as clean as possible before getting it
- Examine dry backplane with flashlight and magnifying glass,
pick out any remaining bits of debris or fluff. If you see green
corrosion on the contacts, it's probably a lost cause, it will never
- Take the backplanes over to your sink. Invert them
(ie, upside down) and use your faucet squirter to spray into them
(while upside down) to flush out debris. Removing the tape that
circles the backplane pins, you can always replace it later with black
electrical tape if desired. If you don't remove the tape it is
very difficult to adequate dry the backplane.
- Allow the backplane to drip-dry for a few minutes.
Pour about 2 liters of 99% (not 70%, not 90%) isopropyl alcohol into a
shallow tray and submerge and slosh around the backplane. Remove,
shake off, dry thoroughly in warm air (a hair dryer works well, or a
- Clean and dry those little top connect blocks exactly as
above. Examine them for corrosion.
- Examine boards. If very dirty or exposed to corrosive
atmosphere or salt spray, consider cleaning, it's easy to do now.
Simply wash in water with your little squirter hose, drip dry, dunk in
alcohol, dry thoroughly in warm air. DO NOT CLEAN THE CORE
PLANE. Examine gold fingers, clean any gunk off. Green
corrosion is a bad sign. Look for component damage, in
particular exploded or deformed electrolytic caps. Make sure all
crumbly bits have been removed or they will fall into the backplane.
- Test power supply, an 8E is a linear supply and will work
without load. Test supply voltages, the -15/+15 are not very well
regulated, the +5 is tightly regulated, I think about 5.3v at the
connector is right. Note the is a DC-OK signal on the power
supply, this is probably about 4.3v to 4.6v. Adjust the power
supply voltages if necessary.
- Re-assemble after everything is dry.
- Have halon fire extinguisher handy.