Assumptions: The right side means the side on your right when you're looking at the instrument's CRT, similarly for the left side.
1. Remove the 4 screws (Torx T20) in the rear rubber feet.
2. Stand up the scope on its rear rubber feet (the rear cover is now loose).
3. Grasp the left and right lip of the front bezel with your fingertips and pull straight up. Using a helper to hold the sheet metal case. I use the tips of my shoes when there is no helper.
4. The inside of the scope should be completely exposed, lay it on its bottom on the work area.
5. Remove 3 long screws (T15) from the top board.
6. Remove a long screw from the middle of the board on the right side. This screw goes through the scope and clamps the power supply.
7. On the top PC board turn two of the plastic expanding clips 90 degrees to loosen the two expanding finger. The two that need to be loosened are on the top, front left corner and rear left corner. (These work by rotating 90 degrees to expand and -90 degrees to loosen. After the two fingers are loose I usually compress them a little with pliers, with age they become brittle and tend not to loosen much.)
8. Pulling up slightly on the left edge of the top PC board alternating between front corner and rear corner (usually called the top sandwich board because it's two boards with a piece of plastic sandwiched between them). You want to swivel the two circuit cards up like a trap door. The hinge is on the right edge.
9. I usually rotate the scope so that the left is towards me and the right side is about 6~8 inches from a wall so that the circuit boards can be rested against the wall when swiveled open. This will prevent the ribbon cables from being stressed.
10. The inside is now exposed. Disconnect the GPIB LEDs mylar cable.
11. Use a socket driver (size ?) to remove the 2 standoffs in the center off the aluminum plate, mark where they go so you don't have a mixup.
12. Remove all screws on the aluminum plate, one screw is perpendicular to the others. Two more screws are on the back of the scope near the BNCs. You'll have to experiment, it should be obvious which two to remove from the back.
13. The aluminum plate over the supply can now be removed.
14. Pull off the ribbon connector (40 cond?) from the power supply.
15. Pull off small ribbon connector from the power supply. This is near the neck of the CRT area. Push the cable and connector into the small hole under the CRT.
16. Pull off the 120/240 voltage selection wires from the spades on the board. Use long needle nose pliers.
17. Pull off the 2 AC input wires. Same method as above. Note these two must be reconnected to the correct spades, do not reverse them when reinstalling.
18. There are 4 plastic compression clamps like the ones on the top PC boards, these must all be loosened by turning 90 degrees. Press the two expanding fingers slightly with needle nose to relieve some pressure and make it easier for the board to pop out.
19. This step I'm not sure how many T15 screws there are holding the PC down also. I believe it's 1 or 2.
20. The power supply can now be removed. Starting from the front edge of the power supply start pulling up. The hardest part here is to get the supply past the 4 plastic (expanding) standoffs. Getting it back on these standoffs can be a bear also.
That's it.
If I missed anything please feel free to add. Remember this is from memory so I could have missed something.
–Victor Silva