TIRE KICK A USED PC
===================

With a few simple tools, you can test-drive a used machine in about an hour.

By: Herb Brody - PC/Computing Magazine

Shopping for a used computer doesn't have to be an ordeal.  Generally, PC's 
age quite well: faulty electronic components tent to perish in the first six 
months, and after that, only a few items are likely to succumb - disk drives, 
power supplies and monitors.  Armed with little more than your everyday 
applications, you can test these components - and the overall quality of a 
pre-owned machine - in about an hour.

Before inspecting your prospective purchase, estimate the machine's market 
value by calling your local computer exchange or consulting The Computer Blue 
Book, from the National Association of Computer Dealers.

The tools you'll need for testing fall into three major categories: 1) copies 
of all the major sofware you plan to run, as well as the release of DOS you 
plan to use, since each version can behave differently on the same machine,
2) a diagnostic program, such as Peter Norton Computing's Norton Utilities or 
Mace Utilities from Fifth Generation Systems, to check the hard disk and RAM: 
and 3) a printer (to test the parallel ports) and a serial mouse and its 
driver software (to test the serial ports).

START 'ER UP
============

If the PC is already running, turn if off and let it cool.  The switch the 
power back on to make sure the computer boots properly from the hard drive. 
Repeat the test four or five times; problems with the hard drive or controller 
are sometimes intermittent.  Also, make sure you can boot from each floppy 
drive using your DOS diskette.

When the machine boots, the screen will identify the make and version number 
of the BIOS.  The BIOS ROM is the engine of IBM compatibility, so you're best 
off with a well-known brand such as Phoenix Technologies, Award Software, or 
American Megatrends, Inc (AMI).  The newer the version, the more likely it is 
to run the latest software.  For example, a Phoenix BIOS version 3.07 or later 
should be safe, as should an Award 3.03 or an AMI BIOS with release date of
8-15-88 or later (visible at the bottom of the screen when the machine boots).

You can't assume full IBM compatibility, and running Lotus 1-2-3 or Microsoft 
Flight Simulator won't help; clone makers can practically hardwire their 
machines for these programs.  So boot and run two or three of the applications 
you use most often.

Listen for odd noises and teltale signs of age: Does the power supply emit a 
high pitched whine?  If so, internal components may have blown, keeping the 
power supply from filtering incoming AC power as well as it should.  Count on 
replacing it.  Does the hard disk squeal or sound like a food grinder 
masticating walnuts?  The bearings may be shot.  Noisy floppy drives, on the 
other hand, are probably in working order.

Check to make sure that each parallel port works by connecting a printer to it 
and hitting the Print Screen key.  To test the serial port, load the mouse 
driver software that you brought along and plug in the mouse.

TAKE THE DRIVES FOR A SPIN
==========================

Next, make sure you can read from and write to each disk drive in the system. 
Copy files back and forth between the hard drive and each floppy drive sereral 
times, checking the directory to see that the transfer was made.  Run your 
software from each drive, too.

To test the floppy drive more rigorously, load it with a blank, unformatted 
disk.  Format it with the /S command, using your DOS diskette.  This creates a 
system disk.  If you can then restart the PC from the new floppy, the drive's 
read/write ability is fine. (The PC had to read the entire COMMAND.COM file in 
order to boot.)

To check the drive's alignment, take this freshly formatted system disk and 
use it to boot a different computer.  If it doesn't work, the drive is 
misaligned, a common malady of aging floppy drives.  It's possible to realign 
a floppy drive, but it probably makes more sense to buy a new one.

Use the CHKDSK command to verify the capacity of the hard drive (you'll get a 
quick verification of system RAM at the same time).  Several diagnostic 
programs can perform more detailed analysis of the hard drive.  Disk 
Technician Pro from Prime Solutions and SpinRite II from Gibson Reasearch will 
tell you the drive's capacity and speed as well as whether bad sectors exist.

One handy program to use when testing disk drives is a puplic domain TSR 
called ERRMON.COM.  This program notifies you each time there is an error 
reading from or writing to a disk.  DOS, by contrast, posts an error message 
only after repeated attempts have failed.

A good source for detailed testing is Alex Randall's Used Computer Handbook: 
The Complete Guide to Buying, Selling, and Trading Computers with a Past, by 
Alex Randall (Microsoft Press).

SCRUTINIZE THE MONITOR
======================

You'll want to inspect the display.  Aging monitors lose there brightness; the 
coating on the cathode gets used up, showering the phospher with fewer and 
fewer electrons.  To test the monitor, remove the antiglare screen and turn 
the brightness and contrast all the way up.  If the screen seems too dim for 
your taste, plan on buying a new monitor; repairing it is rarely economical 
(unless it's an expensive VGA model).

Look for wavering text, flickering, or discoloration.  Let the monitor warm 
up, then examine the screen.  If possible, plug in another monitor to the same 
circuit.  If the two screen images jump concurrently, you can blame external 
interference.

Mose monochrome monitors on the secondhand market display the unremovable mark 
of their previous users - known as a "burned screen".  To check for this, turn 
the screen toward the light.  What you see - perhaps the shadow of a 1-2-3 
template - is ther for good.  If it bothers you, you'll have to buy a new 
monitor.

A color monitor has a life of two to three years of continuous use.  As a 
color CRT's age, the three electron beams that strike the red, green and blue 
phosphors slip out of alignment.  This typically shows up as rainbowlike 
patterns at the edge of a colored area.

Some image problems may arise from sources othe than the monitor itself.  If 
you see dark patches on the screen, for example, the fault probably lies with 
the video card - which is cheaper to fix than the monitor.

CHECK UNDER THE HOOD
====================

Once you're satisfied with the external components, roll up your sleeves and 
look inside the case.  Cleanliness is a good sign.  Even though a thick 
coating of dust probably won't harm the printed circuit boards, the disk 
drives will be similarily contaminated - and that could spell trouble.  Look 
for evidence of manipulation by inexperienced hands - loose screws rolling 
around or cracked circuit cards, for instance.

Examine the solder joints.  Loose connections from a sloppy hand-soldering job 
could cause intermittent failures.  Feel how firmly the chips are mounted.  If 
they're raised up from the board, dust and dirt may have gotten under them, 
possibly leading to damaged chips.

Make sure the power supply is adequate for your needs.  Many older, dualflopy 
systems come with a 63 watt power supply.  If you intend to add a hard disk or 
an internal modem, plan on upgrading to a 150 watt power supply for an XT or a 
200 watt supply for an AT (about $75).

On the motherboard, find the CPU chip and verify that it matches the sellers 
claim.  And if the computer is supposed to have a coprocessor, make sure one 
is there.

You can guage the computer's age by reading the chip labels.  Look for a four 
digit number: the firs two digits indicate the year, the last two digits the 
week.  While older components do not in themselves represent a high risk, they 
do date the computer - an important factor in evaluating such subsystems as 
monitors and disk drives that deteriorate with time.

If everything checks out to your satisfaction, try to get as complete a 
package as possible, including all the manuals, cables, original diskettes - 
even shipping boxes.

Finally, don't get burned with a hot machine.  The National Association of 
Computer Dealers keeps a database of stolen PC's by serial number.  Call its
free hotline service, 800-346-NACD, before you buy. 

============================================================================

Herb Brody, formerly a senior editor of PC/Computing, is a writer based in 
Boston.