Another portable – Compaq 386

I appear to have lost the early photographs, but this machine came to me with the TRS-80 and Compaq Portable, along with a few other laptops and a very, very dead IBM “Convertible”.

Starting out in tradition with a horrible picture- it’s a portable machine. It’s not a laptop by any means, and doesn’t have a battery, so it needs to be plugged in at all times to work. It’s basically just a regular 386 in a very (for the time) small case. Power supply under the solid metal cover, disk drives under the perforated cover.

Compaq in bits

It, the same as the others, had been stored in a very humid location. I had plugged it in outside and it went BANG, let out a cloud of smoke and didn’t do much else.
I closed it up and stuck it out to the front of the street for the trash, went inside and concentrated on the “more interesting” computers.

The day passed and I had mentioned to friends about the equipment, and I was coerced into bringing the poor little 386 in and working on it.
I went outside, wiped most the rain off it with my hand, shook some of the ants off and proceeded to take it apart on the tailgate of my truck to make sure it wasn’t full of critters before bringing it inside.

Once I was sure it wasn’t infested with anything, it came in and was stripped down. (Picture above).

386 motherboard

With the motherboard removed, it was fairly easy to spot the failure. More tantalum caps. Replaced those with some spare regular electrolytics. You can see just how humid it is here, the plating on most of the shielding has gone bad.


With those changed… powered it up and HURRAH. It is alive!

Compaq alive

The thing needed a particular disk to boot each time, as the CMOS battery was bad. No “Press key to enter setup” jazz, this is all done by booting up into a program and setting the thing before rebooting into the OS.
The original battery, a square effort, rated 3.3V, negative top pip- next to the hacked together variant using a laser sight battery ($1.99 for 2!) which was plugged in and has duly been keeping the CMOS and clock alive.

cmos battery

Fitted a 6Gb IDE hard disk, with the cap set to 2Gb, and then written with a low-level formatter to Type 42, the largest the drive controller will address. 570 Megabytes! More than enough, and the new drive is incredibly fast compared to the old one. The keyboard wire is fairly standard but has gone really nasty due to old and damp.

keyboard wire

Recently I was encouraged to put up a dialup BBS. The Portable I was picked initially but refused to run the software (95% PC Compatible!) so the 386 was brought in to save the day. Had some difficulties with the Hayes 1200B SmartModem because nowhere has any documentation for the variant. Spent an afternoon working out the various registers and what changed with each DIP switch setting.

dip switches modem

After a lot of messing about, I got it switched to CCITT signaling and COM2. It worked but the BBS software refused to recognize the driver configuration.

back off

Apart it came again. I was reminded on the Vintage Computer Forums that the Portable 386 has jumper settings inside for various COM port settings. The white box behind the computer is the add-on unit, which clips to the back and provides two full-length 16-bit ISA headers to add various cards. I have the modem and a SoundBlaster Pro clone (incidentally my very first sound card I owned back in about 1994) in there.


Luckily the instructions inside are still intact. The computer has 2 UARTs, only one of which shows up if they are both enabled because it directs the interrupt to the internal socket that is used for an internal dialup modem (top right).

shields down

I don’t have one, so I set up the configuration differently.. ISA slot expansion modem COM1, internal async COM2, Modem COM disabled. Note the add-on RAM (1Mb) and additional 80387-20 Math Co-Pro chip. CPU and Co-Pro both run at 20MHz.


You don’t get to change jumpers much these days on computers. I’d forgotten. Luckily, we get some good results.

BBS booted

BBS software operational! You can see that more vertical lines have ceased to function. I’m not sure if it’s the transistors in the driver chips failing or if the insulation on the ribbon cables is giving out. It a gas-plasma display, basically the same as modern-day plasma TV’s, just it can do only orange.

BBS operational

Final piece de resistance- the Portable I and 386, the I running IRC and the 386 actually at that point dialed in to from New York. It’s running Citadel, when I have it switched on. I need to get a separate phone line for it really. I might pull the screen out again and test the ribbon cables- I need to get my sharp test leads for that though.

Fun times.

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