DIAGNOSING DISK-DRIVE PROBLEMS
by Mark Witt, COG, June 1987

(A basic look at common disk drive problems)

One of the most disconcerting malfunctions on any microcomputer
is trouble with disk drives.  Not only can drive failure result
in down time, but it can cause irreparable damage to your data
and program files.

The symptoms of drive malfunction are files that won't load, disk
write errors, files that contain unexpected information,
diskettes that suddenly won't boot and program crashes.

Very often the drive will read reliably but include garbage data
when writing to a diskette.  This is bad enough when the garbage
is written into Wordstar text, but the entire diskette can be
lost if it occurs in the directory area.

These symptoms will be aggravated by a warm or hot machine.  Do
not subject difficult-to-replace data to suspect drives.

Four disk drive problems are commonly encountered.  We will begin
with the most likely and move to the least likely.


DIRTY HEADS

The best defence here is a good offense.  CLEAN YOUR DISK DRIVE
HEADS!  Purchase a head cleaning kit and keep it handy.  The kit
will contain easy-to-follow instructions and information about
frequency of cleaning.

Dirty heads are not a possible future problem, they're a future
certainty.  All disk drives in use will get dirty.  Not heeding
this warning will leave you some Sunday afternoon with an
unusable computer and no place to get the kit.

If you've had problems and tried cleaning your drive heads and
found little or no improvement, do it again.  The instructions
with the kit will indicate ten- to thirty-second cleanings, but
that assumes no buildup.  If you have been using your computer
for two or three months, you must remove the accumulation.

You may purchase a dry type, but I prefer the wet/dry type.  With
this method you receive one or two diskette-like devices.  They
differ from diskettes in that the media has been replaced with a
cloth-like material.

You apply an alcohol solution to the material and boot the
system.  The monitor will display "BOOT ERROR" messages.

After the time required by the instructions, press Reset and
place the freshly wetted diskette in drive B.  Instead of RETURN,
press SHIFT and the double-quote key to boot the system from the
B drive.  Again "BOOT ERROR" messages will be displayed.

When finished cleaning the heads, mark the date on the head-
cleaner package so you will know when you are due again.

Some head cleaners are less abrasive than others; read the
instructions.  You may be surprised to learn that many head-
cleaning systems meet the ANSI abrasive standards for diskettes.


ALIGNMENT AND SPEED

A second problem is alignment and/or speed.  When the drive is
new, the data pattern is written and read in a specified way and
at a specified speed (300 rpm).  As machines age or are dropped,
the pattern and speed can get out of whack.  An alignment and
speed adjustment to correct this can be done by any computer
repair shop.  It is a good idea to check around for prices, which
can vary greatly.


HARDWARE FAILURE

Hardware failure is an unlikely culprit, but the most expensive
to remedy.

The chain of events that lead to information being written or
read begins with the mother board, in a chip called the drive
controller.  If this is defective, the board should be replaced. 
Next, if you have double density, is the double-density board. 
problems with this will sometimes cause your machine to work
perfectly in double density but fail to write single density. 
Adjustment or replacement of the double-density board is in
order.  See your dealer.

Next, the data is routed through the drive cable to one drive or
the other.  The cable must be seated firmly on the connections
with the connector right-side-up.  Failure here can be caused by
pinching the cable between the case halves (grey case) or
pinching other components and severing a wire,  Sometimes a screw
is driven into the cable during reassembly.  Replacing a severed
or broken cable is the solution.

The next point for the data to flow is the PC board, on the top
side of the drive.  Failure of this board cannot usually be
diagnosed by your dealer, and the entire drive would be sent to a
repair firm for exchange.

The last point of handling is the drive itself, where the data is
written or read in much the same way music is written to a tape
in a tape recorder.  None of these components should take more
than an hour to replace.


EXCHANGED PARTS

Most dealers use exchange parts.  You get a used computer part
that has been upgraded and tested in exchange for your old part
and a fee.

The cost is sometimes as little as on tenth of the cost of a new
part.  Ask your dealer whether the price you have been quoted is
an exchange price.  Try to get an exchange price.  If not, you
have a right to the old parts.  Get them and keep them, as they
might come in handy.


POWER PROBLEMS

If the drive problem refuses to show up when the computer is at
the dealer's or moved to another location, suspect the power
coming into your home or office.  This is the fourth common cause
of drive problems.

In some cases, voltage may be too high for the computer to
operate properly.

The problem is that the computers were designed in California,
where the base line of the  voltage is 110 volts.  Acceptable
voltages there are 103 to 117.  In Chicago, the base line is 120
volts.  Your power will vary between 113 and 127.  Getting in the
higher ranges will cause disk-write errors, screen garbage,
internal Wordstar errors and unpredictable behavior.


SURGE PROTECTORS WON'T HELP

These warning signs will show more as the machine warms.  Most
surge protectors won't solve the problem because the "clamp" at
high levels where physical damage could occur to the computer,
not at levels interfering with operation.  Check the voltage
several times with a voltmeter.  If it is 125+ consistently, it
may occasionally go over 127.

You can call the electric company and report that the voltage is
on the high side and needs adjustment.  Expect the company to
refuse to do anything.  If this happens, ask to speak to a
manager.  If no action is promised, request the number of the
ICC.  Call the ICC, and either the ICC or the power company will
come to your home and put a five-day recording voltage checker on
the line.

Neither party should charge for this service the first time.  If
it is the electric company that puts the checker on the line,
rest assured that it will have corrected the problem before
workers come to your home.
