This is the 3rd post in a 6 post series on the Compaq Portable 386 Computer. In this section we take a look at turning the computer on, getting it to POST, and take a peek at the insides & motherboard. You can jump to:
- First Impressions
- The Gas Plasma Screen
- Booting Up & Opening Up
- The Floppy Drive
- The Hard Disk
- Installing MS-DOS
Now, I, like most people don’t have much patience – I wanted the computer to work out of the box, but as any 32 year old will tell you (myself included): “32 is OLD!” there were a host of issues that were quite difficult to troubleshoot and get working before I could even try to get the computer to boot successfully.
Before we get into that, perhaps it’s best to take a quick tour around the machine to explain all the ports, plugs, drives, slots and buttons.
Looking at the front of the machine, you have the screen, (covered in this previous post). On the left side of the unit you have the standard 5.25” Floppy drive (which can be easily replaced with a much more useful 3.5” floppy drive) and a bay for the hard disk. The right side is taken up by the exhaust for the hot air coming from the power supply unit. On the top you have a comically large, padded handle, running from end to end. Like the screen, it’s is also retractable (the handle makes it so portable and convenient!)
The rear of the unit houses the serial port, the parallel port, an RGB connector (to a RGB display – not VGA or CGA) and also hidden behind a sliding door, proprietary expansion port for the optional expansion box allowing two full length 16-bit ISA cards – essential if you want to plug in a VGA card for an external monitor, sound card or memory card.
Note, that this computer does not have a battery for power – all references to the “battery” on these units refer to a tiny lithium battery used to keep help keep the CMOS memory from forgetting it’s BIOS settings. In fact, most “portable” computers at the time were not designed to be used “in transit”, (like a modern laptop) – they were designed to be moved from place to place and plugged in to AC power at your destination. They were marketed to people who travelled, or who wanted to take their work home with them. (maybe we have Compaq to blame for all those weekends lost to working from home!)
The Compaq Portable III and 386 take a standard “computer plug” (if you really want to know it’s called a C-14 type) and auto switches between 110 V and 220 V. Plugging it in and a flicking the power switch at the back gives a satisfying click and the machine comes to life.
On booting, the computer does some instant basic diagnostics – such as checking the system board for faults, and checking the CPU – if all is well, the screen should instantly flicker on in a nice warm orange glow – followed by a RAM counter to check each KB of installed RAM.
The memory check does some basic checking to see how much (continuous) RAM there is available – including those installed on the motherboard, the proprietary expansion cards, or those installed on a properly configured ISA ram card via the expansion box.
After the ram check, the machine will try to boot using the CMOS settings provided, meaning it will try to boot from the floppy drive using the drive settings specified, then if it can’t find anything a readable disk in the floppy drive, the computer will move on and try to boot from the hard / fixed disk. If you don’t have either setup properly, you will see the message below:
This message is asking you to insert a system or “diagnostic” floppy disk as the computer can’t read the hard disk and needs to boot from it’s floppy drive. If you see this error even with the correct diagnostics diskette inserted, don’t worry, there is hope! Take a deep breath and grab your power screwdriver – you’ll need to open the computer up to clean or replace the floppy drive and also likely replace the hard drive.
I don’t know about you, but I enjoy opening up computers and exploring what’s under the hood – this older computer, however, is particularly interesting as there are a lot of jumper settings and removable parts that can be fiddled with… without too much frustration.
The complete disassembly instructions can be found here. You’ll need a set of Torx (star shaped) screwdriver heads and ideally a power screwdriver. Start by lying the machine screen side down on a flat surface and remove the 6 screws on the back. The screws in the corners a long screws that hold the whole machine together; the two in the middle at the top and bottom hold the rear panel to the rest of the case.
Give the rear panel a gentle jiggle and the rear of the computer case should come out. Pull up then away to reveal the motherboard underneath. For full instructions on the rear panel removal, see here.
The photo above shows the motherboard after the protective shielding has been removed – you can see the CPU and Math Co-processor on the top right, below that on the right edge is the socket for the battery to keep the CMOS settings. On the bottom right you have the serial, parallel and RGB video output ports. Continuing along the bottom edge, in the centre you will find the ribbon cable connection for the graphics card underneath, past that is the connection (and space) for the hard-to-find 32-bit memory modem expansion interface for the modem card and the memory expansion boards (which can provide up to 10 MB of RAM).
It’s more than likely that one or more of the items below will need to be repaired or replaced, luckily assembly and disassembly of this computer is relatively easy.
- Hard Disk – these are one of the first IDE drives developed ranging from 20 – 300 MB. Due to the age, they likely won’t spin up. If they do, download and archive whats on the disk while you can. You can replace this with a Hard Disk or better yet, a CF Card
- Floppy Drive – 32 years is a long time to accumulate dust. Take a look under your fridge for reference. These wide-mouthed 5.25″ floppy drives usually are very dusty and thus fiddly to get working consistently. Be ready to change drive belts and apply lubricant to get them fully working, or, more than likely, you will have to replace it. Alternatively, you can easily upgrade the floppy drive to a 3.5″ – covered in this post.
- CMOS Battery – You will need this to keep the CMOS system settings in the memory alive. Believe it or not, there are some people who have these units where the lithium battery is still ticking and giving current for the CMOS to save settings. You don’t really want to count on that though, and it should be replaced – a CR2020 3v button battery makes a good choice. I simply snipped off the connections to the old battery and sandwiched a CR2020 between the leads, checked it with a multimeter and then secured it with electrical tape.
- Visually inspect the Motherboard – to check for jumper configurations, any blown capacitors, and also see if you happen to have any optional (and extremely expensive) memory expansion boards. These are so rare that one seller on eBay has listed a unit with one of these installed at US$999.99 – here’s my 10MB upgrade card below – it’s aftermarket, made by Kingston Technologies.
So hopefully you now have an idea on what you need to replace. If you have to replace both the floppy disk and the hard disk, or if you are not sure if your hard disk is working or not, and your floppy drive is not working, definitely, replace the floppy drive first.
If your floppy drive is working but you can’t get boot to your hard disk, see what your choices are for replacing the hard disk