Compaq Portable (Original)

The Compaq portable was one of the first of the IBM PC clones. It came in a "luggable" form factor, with a built in green monochrome monitor, PSU, dual 5.25" floppy drives, and internally connected detachable keyboard.

Causes

 * The Portable made use of a "foam and foil" key switch design, a type of capacitive switch wherein the key presses a plastic-foam-foil sandwich onto a set of contacts. Over time, this foam degrades to the point of disintegrating at the touch.

Solutions

 * New foam and foil pads can be fabricated by hand (see here) or purchased (here) when in stock.

Display turns off after a few minutes
(Discussed in detail here)

Causes

 * Fault in the analogue CRT control board.

Solutions

 * TBD

Disassembly Notes
Disassembly is also covered in the official service manual, linked at the bottom.
 * The outermost case has two removable plastic panels on the top and bottom They are attached by clips on the back (the side with the handle). I recommend prying outward at each clip with a plastic prying tool, working from one side to another, using clips or other tools to hold previous clips open as needed.
 * Under the plastic panels is a metal inner case. Most all inner case panels can be removed by loosening the flathead screws and a few nuts (these can be removed, but do not need to be removed to remove the panels). On the top, there are panels covering the three main sections of the inner case: the ISA slots, Floppy drives, and monitor/PSU section.
 * The ISA cards are fairly standard if you are familiar with IBM clones. They are screwed in to the case on the external facing side and fit into plastic grooves on the opposite internal side.
 * The floppy drives are screwed in on the top and bottom of the machine. To remove them, you should first remove all of the ISA cards, unscrew the drives, and pull them back towards the handle side to be lifted out from the card area. The front plastic drive covers and latches can remain attached during removal. There is an additional metal cage screwed onto the drives, which can be removed to access the drive heads for cleaning.
 * The CRT control board is attached by one screw and three plastic standoffs. To remove it, remove the screw and pull the board upward to remove the plastic standoffs from their slots, removing the CRT cap connector and other cables as you go. I found it necessary to remove a zip tie retaining one of the cables attached to the board. This is very difficult. Feel free to curse.
 * The motherboard power connector and motherboard keyboard connector are accessible from the bottom of the machine. After removing the outer plastic panel, remove the small metal panel by loosening the screws, as you have done on the top of the machine.
 * The keyboard is held together with many, many screws. Keep track of which type of screw goes where. In the top right corner there is a voltage regulator which produces a significant amount of heat during operation. This heat is normally dissipated through the metal metal key assembly with thermal paste. For testing with this assembly removed, you can stack coins on top of the regulator. This is much less effective at dissipating the heat, but is better than nothing.
 * Four small plastic clips retain the hard plastic backing of each foam and foil pad. When replacing these, the backing  can be pressed into the clips with a fingernail or pointed object.

CRT Control Board
''TCI-A1S (AIS?) 94V-0. Also labeled 204-1265B. Located within the monitor assembly. NOT the video card.''

This table only contains the Electrolytics at the moment. There are also other types on this board.

IMPORTANT: C401 may be installed backwards from the silkscreen; the silkscreen is wrong in this case. With the board oriented with C401 at the top, the negative lead should be on the left.

CRT Control Board
''TCI-A1S (AIS?) 94V-0. Also labeled 204-1265B.'' If parts are not available or different selection is preferred, you can use the values in the Original Parts section to perform a parametric search.

Kits

 * Mouser Project

Related Links

 * The Official Service manual (for the original, Plus, and 286 models)