They said it couldn't be done-- and they were almost right.

My friends told me I was plumb loco even to think I could manage to build my own 16-bit, IBM-compatible, MS-DOS personal computer. They told me I would end up buried in a pile of microchips and permanently scarred with burns from the soldering iron.

Did I listen to this perfectly reasonable advice? Of course not. I was determined to build my own computer. This seemingly wacky idea came to me while I was browsing through the catalogue of the Heathkit Co. (Benton Harbor, Mich. 49022). That venerable maker of ham radio, TV, and other electronic kits now lets you build your own IBM-PC clone.

Heathkit is a subsidiary of Zenith, and one of the kits in its current catalogue is a do-it-yourself version of the Zenith Z-150 PC, a terrific computer that is just about 100 percent IBM compatible. As soon as I saw it, I started muttering about how much fun and how economical it would be to put together this "easy-to-build" (that's what the catalogue said) computer.

My friends wondered why I would bother with a kit. After all, the Zenith Z-150 is available fully assembled from many mail-order houses at about $2,200 for a two-drive, 320K computer with monitor and bundled software. How much, they asked, could you save with that stupid kit?

In fact, I did save some money by buying the kit. I got it on sale at my local Heath/Zenith store for about $500 less than the lowest mail-order price.

The basic kit, with monitor, one floppy disk drive, and 128K of memory, cost $1,458, a price that included MS-DOS, Microsoft WORD, and the Multiplan spreadsheet. Most computer dealers would have charged another $300 for a second disk drive and about $250 to install another 192K of RAM memory. But since I was building the thing from scratch anyway, why pay a dealer's prices for all that? Instead, I shopped around and bought one of the Mitsubishi drives that Zenith uses ($145) and 192K worth of RAM chips ($80) and installed them myself. That brought the total bill to just under $1,700 for a powerful machine complete with powerful software.

More important than the dollar savings, though, were the knowledge and the sheer satisfaction I expected to gain from building a computer with my own hands.

I did gain some knowledge. After hours and hours of putting it together, I feel intimately acquainted with the inner circuitry of this machine. If anything goes on the blink, I expect to fix it myself.

Satisfaction, though, I did not gain. If anything, the construction of this computer was an exercise in tedium and exasperation. The blame for this belongs partly to me -- I am sloppy at soldering -- but largely to the folks at Heathkit.

Opening the huge box containing the Heathkit H-151 computer is a terrifying experience. Out of that box spills dozens of chips, scores of resistors and capacitors, piles of connectors, and countless caches of nuts, bolts and minute screws. Somehow, this motley collection of loose hardware is supposed to turn into a computer.

To make that happen, Heathkit provides extensive instructions and schematic drawings. Over the decades, Heathkit has earned an estimable reputation among electronic hobbyists for its clear, accurate instruction books. But the instructions that came with my computer kit did not meet that standard.

In some cases, the instructions were flat wrong. After I had devoted hours to the construction of the computer's backplane board, I ran through the voltage and resistance tests set forth in the manual. I spent days ripping the components out and putting them back together, trying in vain to make my board pass the test. Finally, I placed a desperation call to an engineer at Heathkit, who told me all this effort had been in vain: The instruction book had the test wrong.

Elsewhere, the instructions were difficult or impossible to follow. The picture illustrating how to install two crucial cable connectors, for example, showed different hardware from that provided with the kit. The instructions called for a connection to "Pin 14" of a logic chip -- but didn't bother to explain which of the many pins was No. 14.

Some other aggravations were not Heathkit's fault. I vividly remember a day when I walked into the workshop and found -- to my horror -- my 1-year-old perched atop the computer chassis, contentedly chewing on a memory circuit. Both child and chip survived intact, but I am still recovering from the shock.

With all these distractions, building the computer -- a task Heathkit estimates at 20 to 30 hours -- took me nearly two weeks and several long-distance calls to Benton Harbor. It was more frustrating than fun.

Still, my tale of woe has a happy ending. All that loose hardware did indeed turn into an excellent computer, and I'm delighted with it. In this space next week I'll explain why the Z-150 is so fine.