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STUFCHIP.DOC
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1983-05-03
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15KB
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259 lines
HOW TO STUFF YOUR OWN BOARDS WITH CHIPS
By Louis A. Warner, P. E.
PEOPLE SYSTEMS LTD. -- SOFTWARE (C) 1983
You have just purchased some of the finest devices
that have ever been produced. These chips need
special attention if you want to get the best out
of them, because they are very easily damaged by
static electricity, that you and I wouldn't even
notice. No snap, crackle or pop, but zowie, there
goes a good chip, destroyed by static electricity.
There are ways to protect your investment against
such damage, if you're careful and take your time.
Before you unpack the chips think of a pettigree
puppy that you just purchased, and treat it
tenderly and you'll enjoy. Oh, yes, don't open up
the chips until you're ready to install them.
Remember static electricity hates humidity, but it
loves nylon and synthetic clothing, soft rugs and
slippery shoes. Static is worse in the dry winter
weather, and least in the humid summer time.
Before you unpack your chips, have you read your
owners manuals for adding chips to the main memory
or an expansion board? Refresh your memory and
plan your project and you'll do it easily. It's
really not very hard to do and unless you get
rough with your equipment there is little you can
harm if you take precautions. You will need a big
sheet of aluminum foil, a spray bottle of water, a
boiling teakettle and some light hobby tools,
flashlight, magnifier, pad and pencil along with
the manuals etc.
A clear, clean kitchen table on a linoleum floor
where the light is very good is a fine place to
operate on the patient. Take your computer cabinet
off to get at the board you're going to stuff.
Read your manuals or ask your buddy's help to get
it unbuttoned. On the IBM-PC there are two large
screws in the lower rear corners, near the curve
at the bottom of the back. Slide the cover forward
and put it aside. Vacuum the fan and inlet areas
carefully, but don't let the air from the vacuum
stir up any dust in the room. Wiping the fan
blades with a tiny brush will help it do its job.
Remove the rear hold down screw from the expansion
board and gently raise the board from the bus
socket on the mother board. Place a large piece of
aluminum foil flat on the table to touch and
ground yourself on when you're working on the
chips. If you have a battery powered board (clock
etc) remove the battery. You are now ready to open
up your chips and set them into the open sockets.
Review your conditions again. Shoes off, tea
kettle boiling, dog and cat out of the house, kids
gone to the movies, you are ready to operate,
Doctor.
What do you do in the winter or when the humidity
is real low? Wait for a rainy day or raise the
humidity with a vaporizer in the room. Don't wear
synthetic clothes. But use a spray bottle to keep
from getting too dry. Mist your clothes and the
floor and chair seat (usually plastic too) with
water to keep it from generating static. Don't
work on rugs, if possible, or else spray them with
static guard and water mist. Look-out for nylon
lingerie whether you are stuffing a board or
whatever. Don't get your computer wet.
You have unwrapped your chips and the board is
sitting on the aluminum foil waiting for the
chips. Stand your chips, pins down on the foil and
examine one carefully, while touching the foil.
There may be a production number marked on the
underside, in case you need a reference mark. They
can also be marked with ordinary pencil lead if
you write small enough. Note the indentation at
one end that indicates the number one pin end.
Find out which way it should go in your board. The
pins taper outwards and need to be gently squeezed
together into two straight lines.
Press the side of the pins (lengthwise) against
the table to align and narrow down the spacing
between the lines. Do it again for the pins on the
opposite side. Now set it on the socket gently,
check direction for the dimpled end (socket covers
have been removed, if they existed). Inspect it
carefully, with a magnifying glass, if available.
If the pins line up with the contact holes
properly, then use your two thumbs and steadily
press it into the socket. You will feel the socket
grab the pins, but dont try to test its holding
power. It's hard to get them in but much harder to
take chips out of the sockets. There are special
chip tools that are available and are well worth
the money, if you are going to do much pushing and
pulling. Or you can use a couple of small
screwdrivers as wedges. But gently! Now take your
glass and inspect the chip pins for one that might
have been folded under when you pressed it in and
it was not in line with the hole. Inspect each pin
carefully for a few chips and develop a secure
feeling that you are doing it right before you
proceed too far.
When the board is stuffed with one full set of
eight or nine chips, (populated as they say) and
you have reset your switches properly, it is best
to test, doctor. But first, look around and read
the labels and signs so that the inside of your
computer isn't such a strange place next time you
have to dig under its covers. You probably feel
like the radio receiver owner, when he first
changed a tube, years ago. But it's just another
piece of hardware to get familiar with. Don't
touch but do look, ask questions, and read the
manuals. Take a photo or two.
Now, doctor, lets plug it in and test each set
before we suture up the patient, and put on the
cabinet again. Install the operating cables and
put the boot disk in the A: drive and turn it on.
Remember that with more memory its going to take
more self- diagnostic time, so dont be surprised
if 256K takes over a minute before the CPU
beeps,"All present and accounted for, Sir". Then
your normal boot routine should begin. Watch
carefully for error messages on the screen and
write them down. If you have parity lights on the
board note them and shut the power off in case
there is not a normal boot sequence (except for
the longer memory check at the beginning.)
DON'T PANIC -- SLOW AND EASY IS THE GAME -- THIS
HAS HAPPENED BEFORE AND PEOPLE LIVE THROUGH IT.
Here's a list of what could be causing a
malfunction, IF THERE IS ONE! The switches on the
board and in the computer could be set wrong,
recheck them in writing. Have someone else double
check you. There could be a bad chip. (We'll tell
you how to look for it). You may have disturbed
something in your cleaning or reassembling the
cables and case. Make sure everything is properly
turned on for the test. There is also the remote
possibility that the expansion board is defective
or intermittant in the section you have just
stuffed. Examine the solder joints on the printed
circuit board in these areas. Retrace your steps
and restudy the manuals, check the switches and
then try it again after a short period. Shut it
down if it still doesn't boot properly and once
more check all possibilities. The chip failure
probability is less than any of the other
possibilities, especially wrong switch settings.
Remember there are totals of the PC mother board
chips, total of the expansion board's memory,
total of other boards like a C/PM adapter memory
and then the grand total of all RAM installed.
Check them by writing them down and see if the
switches are correctly set, one by one. Then if,
you find that everything is O.K. but it still
doesn't work the way it should, continue on.
Let's see if there is a bad chip. This is usually
the first assumption, but most often it is switch
settings or bent pins or bad sockets that make
intermittant contact or some silly thing like
leaving the keyboard unplugged. Since taking the
chips out is a stubborn operation that doesn't
improve with brute force, let's plan our attack.
If we have a couple of spare chips we can try them
in another working circuit on the board and reset
the switches. Go back to where you started. Ground
Zero we shall call it. Usually, you dont have to
pull the chips just reset the switches and try out
the old chips under the original conditions
(before stuffing). Put the board in and test it
again. It's probably O.K. and you haven't done any
damage. But electronic gremlins aren't called
glitches for nothing.
Now swap the new spares to determine if they work
in the working circuit. Yup, they work O.K. Now
let's start a planned procedure to reduce the
confusion and the number of times we have to push
and pull the same sockets and chips. We don't want
to damage our board or the chips with too much
handling or abuse. If you stuffed three sets of
chips without testing each set and the last one
shows the parity error then take those out to
test. Work your way backwards, one set at a time,
until you get to a working state. Remember to
reset the switches correctly each time you test
another full set of chips. You can not test
partial sets although they can usually remain in
the sockets if you know they are good. But, when
in doubt, take them out.
Now test three chips at a time and mark them. Put
nine that tested good in the old circuit into the
next set of sockets. If you only have one extra
chip, borrow the parity chip, and turn off the
parity reporting until you locate the bad chip
(probably only one, IF ANY). By testing your chips
two or three at a time in the working circuit, you
can isolate the bad group then test them one by
one to find the culprit, if there is one.
When you get through testing and stuffing, you'll
find there is nothing wrong with any of the chips
and they all work fine. There apparently was a
temporary glitche the first time around that
issued the parity error and it took a while to
discharge a condensor or change a flag or
something. That's why, when you buy a pocket
calculator, they tell you to turn it off and on
several times, if it doesn't work properly the
first time.
Try to keep track of your tests and actions on
paper so that you can isolate a bad chip or
convince yourself that it's something else that's
wrong. Mark the chips with a pencil or note the
production marks that should identify them
uniquely. For your own piece of mind when you
think that you have found a faulty chip, after all
else is done, test it to prove it's bad in a
working circuit, one chip at a time.
Don't be surprised if it tests good now. That's why
manufacturers call it "burning in". (Finding the
good and the bad actors). But usually the
percentage of bad chips is miniscule unless there
is a run that quality control didn't catch before
it left the plant, which is almost unheard of. If
it now works, burn it in. Leave a colored mark on
any suspicious ones, just in case you need to
locate an intermittent one in a couple of days or
so. Keep a written record of them also.
If you are using the same set of sockets to test a
lot of chips, alternate the sockets so that the
same ones don't get all the wear. Be careful not
to pry against any of the small electronic
components and damage them.
Good luck stuffing -- you'll find the experience
worth while and not hard at all once you get the
knack of it.