Released 1988: Compaq SLT was a line of laptop computers made by Compaq. Two models were produced in the SLT series. The first model, Compaq SLT/286, is considered to be one of the most notable units in laptop history due to its battery life and superior performance compared to competing models. It is also notable for being Compaq’s first laptop computer.

Facts

  • Manufacturer: Compaq
  • Type: Laptop
  • Released: 1988
  • Base price: $5,399
  • OS: Compaq DOS 3.1
  • CPU: 80C286 @ 12 MHz
  • FPU: optional 80287@12 MHz
  • Memory: 640 KB (expandable to 3.6 MB)
  • Display: 10″ grayscale LCD, supports 640×480 with 8 grades, 320×200 with 16 grades
  • Graphics: VGA, port for external VGA
  • Storage: 20 MB or 40 MB (additional $600) hard drive
  • External media: 1.44 MB 3.5″ floppy drive
  • Audio: PC speaker (1 bit mono)
  • I/O ports: serial, parallel, docking unit, VGA, 5.25″ FDD, keyboard
  • Dim: 13.5″ W x 4.2″ H x 8.5″ D
  • Weight: 14 lb. without battery (6,3 kg)
  • Predecessor: Compaq Portable III, Compaq Portable 386
  • Successor: Compaq LTE

SLT/286 was the successor to the Portable III and Portable 386 and the predecessor to the more well known Compaq LTE. The SLT/286 had a 12 MHz Harris or Intel 80C286 processor (both brands were used throughout the SLT/286’s production) and a grayscale VGA LCD screen, the very first laptop with this feature. The price started at $5,399 for the base-model.

Compaq’s main marketing message for the SLT range was its battery life, up to three hours minimum. Battery life benchmark test in InfoWorld November 14, 1988 proved two hours and 25 minutes. Compaq mentioned this feature in almost all of the SLT literature. Moreover, Compaq released an external battery charger to enable the business user to charge up multiple batteries.

Compaq offered a variety of options for the SLT – even if you selected only a few, the price of the laptop could quickly escalate from its $5,399 base price. For example: 2,400-bps internal modem ($599), extra battery packs ($129 each), a desktop expansion base/docking station ($999), carrying case ($89), MS-DOS 3.31 ($120) or OS/2 version 1.0 ($325).

My Compaq SLT/286 and repair
First I did the usual clean and wash. My SLT/286 was powering on, but wouldn’t boot from the hard drive. The CMOS battery with the hard drive settings was dead,  this is very common. In this machine the CMOS battery is integrated into a “Dallas” chip which was soldered directly onto the mainboard last probably around 10-15 years or so before its flat.

Compaq SLT/286 - using an external monitor
My Compaq SLT/286, Space Quest III – using external monitor
  • Dallas chip: I’ve cut into the Dallas chip using a carpet knife to get to the two leads going to the integrated battery. I’ve cut off the lead to the battery GND off with a plyer. Then I soldered on a wire from the GND and positive lead inside the Dallas chip. I’ve routed the wired to the battery pack compartment and soldered on a coin cell type battery holder for a common LR 2032 battery. After this I could boot the “Diagnostic” floppy disk to configure the CMOS for hard drive, date and stuff. And then the machine booted into MS-DOS from the hard drive.
  • Hard drive: My machine came with a 40 MB hard drive, and it seemed to work fine at first, booting up without errors. But after some testing I found that the hard drive got a lot of bad clusters and was in a kind of a poor state. I then replaced the hard drive with an IDE-CF adapter, that  wouldn’t work at all typically for all PC’s, so I ended up using an IDE-SD card adapter instead. I was then able to setup a 255 MB or so hard disk size using the Diagnostic floppy disk to config CMOS. I’ve measured the voltage on the machines non-standard power connector for the hard drive and soldered on a standard connector. I’ve made an y-split so the existing 40 MB hard drive could be powered on as well, if I later want “authentic” noise level. By not removing the original hard drive, the machine also keep the correct “weight”. I’ve positioned the IDE-CF card adapter together with the coin-cell battery in the battery pack compartment, for easy access.
IDE-SD adapter and CMOS battery in battery pack compartment
My SLT/286 – IDE-SD adapter and CMOS battery fitted in the battery pack compartment.
Compaq SLT/286 - backside brochure
Compaq SLT/286 – backside brochure
Compaq SLT/286

Remi Jakobsen


I'm collecting classic computers and video games, stretching from the 70's into the 90's. Restoration, history, usage ...


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