tkc8800

Technology and retro computer blog

Compaq Portable II Restoration

I recently acquired a Compaq Portable II.  It was great to get hold of this machine because I have the Compaq Portable I and III, so this completed the set.  This machine was somewhat of a basket case, the video board was defective and was preventing it from starting.  Initially on power up there was a beep and a red flashing light on the front.  The seller was good enough to diagnose this before I bought the machine and supplied a replacement IBM EGA (IBM 6278173XM), board to get the machine running.  The EGA board allows the machine to start up but it doesn't have the connector to drive the internal CRT, so you have to use an external monitor.  The 360k 5.25” floppy drive in the machine worked but the door was very sticky and wouldn’t open or eject disks properly, but luckily it read disks fine.


IBM-6278173XM_EGA_board.jpg
IBM 6278173XM EGA board


Another problem was that the hard drive only worked once the machine warmed up.  This is a classic case of "sticktion" where the head is stuck from being inactive for many years.  The hard drive is the original 20mb MFM drive (type 2).  It has the MFM to IDE converter board attached to the bottom, so it's a great piece to have, but considering the reliability issues the plan was to replace it with a later model IDE drive or CF IDE adapter.  At least when the machine was booting from the hard drive it was evident that everything was working.



The defective GA2 video board


Onto disassembling the machine to get to the drives and boards.  I found a copy of the Compaq Portable II service manual online which had directions on how to disassemble the machine.  Disassembly of this machine is quite different to the Compaq Portable I, I had to refer to the manual to work it out.

Compaq Portable II - Maintenance and Service Guide.pdf



One of the first tasks was to remove the floppy drive and service the eject mechanism.  I used some lithium grease on the hinges and on the head mechanism.  The heads also got a clean with a cotton bud.  This got the eject mechanism working smoothly.


In order to test the internal CRT the video board from my Compaq Portable I was installed.  The connector for the internal CRT is the same on both machines.  Connecting the internal CRT cable required some re-routing through the case, as the connector is at the other end of the board.  Once connected the internal CRT worked fine.  The picture geometry and brightness were all really good.  The video board from the Compaq Portable I works in this machine but it’s considerably taller and protrudes out of top so you can’t get the case back on.  So it’s only a temporary fix.




Now that the internal CRT had tested successfully it motivated me to get a replacement video board.  A search on U.S Ebay found several Compaq Portable video boards for sale, but they were rather expensive considering I have to pay international postage and exchange rates.  I found a listing for a later model video board (Assy no. 000525) for a reasonable price so I bought it.  This video board is listed in the Compaq Portable II technical manual as an option so it’s an appropriate replacement.


Having sorted out the video issue for now my focus shifted to replacing the hard drive.  I have several newer IDE drives but they’re all fairly large by the standard of the Compaq Portable II.  The smallest I have is 40gig.  The Compaq Portable II setup disk only caters for a selection of specific drives and none are anywhere near that capacity.  I’ve read that these larger drives can be used with the assistance of a BIOS overlay which is specific to the drive’s brand.  I instead decided to try using a compact flash IDE adapter that I have.  Trying several hard drive types using the Compaq Setup utility, I eventually succeeded with the 20mb type 2 hard drive option.  The CF card in use was 1gig, so it wasn’t a very good  use of its capacity.  I have a couple of smaller CF cards that are closer in capacity to those in the setup utility, so I’ll try to get one of those working later, but at least for now the 1gig card works.



With the convenience of having the CF hard drive working I was able to easily copy some applications over to the Compaq Portable II.  I loaded up several games and installed Windows 3.  I also plugged in a serial mouse to use with Windows, everything worked fine.



The machine has several extra boards installed, an Analogue Devices CT-180 which is an analogue to digital controller board.  It also has an SMC network card.


SMC_8_bit_network_board.jpg
SMC network card
Analogue_Devices_CT-180.jpg
Analogue Devices CT-180

Update: I've now managed to get a 160mb CF card working as a type 25, 134.5mb hard drive.  So only around 25mb of this  card is lost.  After using the DISKINIT utility on the Compaq setup disk I could see this CF card as the C: drive, but I couldn't boot from it.  On restart with boot floppy removed, the system would just stop booting with a blinking cursor in the top left of the screen.  I fixed this by running the following command:

A:\FDISK /MBR

This fixes the master boot record of the disk (CF card).  Once that was done the machine now boots from this CF card fine.




Compaq Portable II post 2:

New video card and sound card for Compaq Portable II
Comments are closed