Tuesday, June 7, 2016


  The Compaq Portable III is a computer released by Compaq Computer Corporation in 1987. It was advertised as being much smaller and lighter than the previous portable x86-PCs, however it was still quite large by today's standards.

  Its street price upon its release was 4999 USD for a model equipped initially with an 12 MHz Intel 80286 and later 20 MHz Intel 80386 CPU, 640 KB RAM,1.2 MB 5.25" floppy, 20 /40 /60 MB hard disk, and a 10" amber colored gas-plasma display or 5799 USD with the upgraded 40 MB hard disk. There was also an optional ISA Expansion chassis allowed for 2 full length 16-bit ISA add-in cards for 199 USD. Power is supplied using a mains electricity outlet, no battery exists.



It seems Thomas and I started a new project.... We want to restore a COMPAQ Portable III machine from the scrap to its initial glory. However we got stuck...

The Compaq Portable Thomas got has a broken power supply, after spending some time with the user manual we started by disassembling the unit.

The CP III upside down (back view)

After removing all the screws stated in the user manual and all the connectors. the supply just wouldn't slide like shown in the below picture from the manual:

Clearly the age of the machine makes everything harder to work with. After multiple tries we got it apart.

Compaq Portable III Power Supply

Inside the Power Supply:

Inside the Power Supply_Picture_1
It seems the supply looks good except for the broken fuse. Thomas couldn't wait for the new fuse to arrive at a local shop the next day, so he made some solder construction with copper wire tape and more solder in order to make the connection directly without the FUSE in place but something went wrong...
The supply got assembled back again, tried to power it on but all we got was a BOOM sound... After that we noticed some smoked area. See below pictures:

From Picture_1 you can see the FUSE was already broken, but I can`t remember if the smoked area was already there or it happened after the soldering. It seems logic that it could be there already as the fuse was already broken...

Anyway, the power supply looks toast.

I can see here some options:

1) Buy a working power supply (not sure that we will find one)

2) Get the power supply schematics and replace all broken components

3) Find a very good electronics engineer that can replace everything and test component by component all the power supply. 

Does anyone have some schematics regarding this POWER SUPPLY?

Can anyone provide us some tips?

Thank you in advance!


  1. Hi ,

    I can make some messurements on my spare one....

    I have three compaq portable's

    1 x 386 fully restored
    1 x 386 needs some restoring
    1 x 286 fully restored

    did u see the kind of memmory they used ahah long strips........


    Kluunsoft Retro


  2. Hi Unknown :) If you can make some measurements of the power supply outputs it would be great. This project is now on Hold because of the power supply... :(