A Very Basic Guide to Home Computer Assembly
Table of Contents
- Intro
- What exactly do I want?…………………………..4
- Verify all the parts………………………………...5
- Prep the work area………………………………...8
- Hazards to consider……………………………….9
- How and where to begin…………………………..9
- Cabling…………………………………………...12
- Pre-Startup checks…………………………….….15
- Power-up…………………………………………15
10. Trouble shooting………………………………..16
1. Intro
First let me say that this document is in no way intended to promote any manufacturer, architecture, form factor, “insert name here” format, processor type, socket type, slot type, or any other hardware bit, byte or nibble over any other. For that reason this document will remain as general as possible while still presenting information that should be useful to the novice Hardware Systems Engineer. As individual experience grows one finds that most of the “Oops and got ya’s” are interchangeable in regards to machine type anyway. As all PC’s trace their roots to the IBM Model 5150 PC it never ceases to amaze me as to the resilience of legacy, especially when it comes to errors. A “301” error is still a keyboard error and anything starting with “17” is very bad news for a disk drive. I did however receive a “401” error from a modern system board which was odd as Monochrome Video went out with Bell Bottom Jeans. A sound card that had failed was using the register and the BIOS just gave a best guess. At this point, take a deep breath and say to your computer; “I’ve got a screwdriver, and I’m not afraid to use it.” Let’s begin.
2. Exactly What Do You Want from this Computer?
Before you purchase any parts you must ask yourself one fundamental question. “How is this computer to be used?”
Will it be a gamer, a music workstation, a fileserver, the list goes on and on but the answer will have a profound effect on the design of the machine. A gamer will need a graphics card which may be more powerful than the computer itself with memory to match where a fileserver may be controlled via a VT-100 serial link and have no video sub-system at all. A basic checklist can be very useful in assuring the final system is configured in a manner fitting the need and that all parts match one another. Examples of questions, which should be addressed,
What processor will it use? (e.g. AMD vs. Intel)
What form factor will be used? (ATX, mini ATX etc…)
What Graphics card type will be used? (AGP, PCI-X etc…)
How much memory do I need and of which type?
What family of disk storage will be used (ATA, SATA, SCSI etc…) and will it be configured as a RAID?
What type of sound support will be required?
What removable storage devices will be used? (CD-RW, DVD, USB, Fire wire, Compact Flash, etc…)
And lastly what type of Human interface devices will be used. Oddly this is a category that gets little attention but can greatly affect the overall usability of a computer.
3. Verify the Parts:
Once a checklist of parts has been developed, the parts need to be checked for functionality and compatibility. Major subsystems will be covered individually in outline form for clarity.
a) System Board:
-Does it have the embedded features that you want?
-Are there embedded features that are unnecessary or possibly problematic?
-What processor type will be used and does the system board support the desired processor?
-Does the manufacturer have a history of supporting boards in the field with CMOS updates and bug fixes?
-What are the boards power requirements?
-What type of Video subsystem does it support?
-How many memory slots are available and what types of RAM are supported?
-How many embedded disk controllers are included and of which family and type? Are they RAID capable?
-Does it include the required mounting hardware, backplate, and I/O cables?
-Will it fit the chassis you intend to use?
b) Chassis:
-Does it support the form factor of the system board?
-Does it have the front and rear panel I/O and other features you desire?
-Does it use standard power supplies or does it require a proprietary power supply?
-Does it have the required number of drive bays and in the correct size?
-Does it have adequate cooling for all installed components?
c) Power Supply:
-Is it rated at sufficient wattage to support the desired configuration?
-Does it support the system board? (e.g. 20 pin ATX, 24 pin ATX, 4 pin 12v P4, 6 pin 12v for Athlon , SATA power Etc…)
d) Processor:
-Does the processor pin grid match the pad on the system board?
-Is the cooling system capable of handling the heat load?
-Will the cooling complex fit the chassis?
e) Memory:
-Does the memory match the system board?
-Are all memory boards of the same type? Many system board manufacturers state that you can mix memory so long as all memory within a specific bank are matched. This practice should be avoided. Memory timing issues can cause unstable operation and are usually very difficult to diagnose.
f) Graphics:
-AGP or PCI-X? (make sure it matches the system board)
-Can the power supply handle it? (many graphics cards require auxiliary power directly from the power supply)
-Will cooling requirements be met? (A massive heat sink may block an adjacent slot but fans have always been a
weak link.)
-Necessary Graphics I/O ports. (DVI, XGA, S-Video etc…)
g)Mass Storage:
-Does disk match the installed controller? (IDE, SATA etc…)
-Is the drive large enough for intended use?
-Will the disks be part of a RAID?
h) Sound Support:
-Will the embedded sound device be sufficient?
-Will this machine be used as a MIDI controller?
-Are the required outputs available? (Multi-channel stereo, Optical Audio, Digital audio etc…)
i) Removable Storage:
-What type of removable storage do I need? (CDRW, DVD, Compact Flash, SD cards, Floppy disks etc…)
j) System I/O devices:
-Does the system board have all the ports I require or will add-on boards be required? (RS-232 serial ports, Parallel printer ports, Ethernet ports, USB, Fire Wire, etc…)
-What type of keyboard and pointing device will I want?
(PS/2 keyboard, USB keyboard, keyboard layout, trackball
vs. mouse, etc…)
4. Preparing the Work Area.
There are four main considerations when selecting a work area.
-Static Control. A static mat with grounding wire and wrist strap should be used whenever possible. Should one not be available, always be sure to have direct contact with the bare metal of the computer chassis prior to removing any part from it’s static bag. This will help ensure that all parties are at the same potential and no discharge will occur. Weather can play a major role in static build-up. As an example, on a cool dry day the static hazard will be considerably higher than on a warm humid day. With this in mind, if the relative humidity is below 25% you may wish to postpone the work altogether. Waiting a day or so will be less expensive than replacing damaged components.
-Tools. The most common tools required will be a #3 phillips screwdriver, a ¼” nut driver, a small adjustable wrench and a set of needle nosed pliers. (for those pesky dropped screws and awkward jumpers/front panel cables)
-Light. Always try to have a small flashlight handy. There is never enough ambient light to read the white id markers on system board but a large lamp will create too much glare to be of any use.
-Dust. While it cannot reasonably be expected that you provide a “clean room” environment, the work area should be as free of dust as possible. As you begin troubleshooting computers you will find that simply removing and
re-seating components will clear many problems. This is
dust. With connector tolerances as tight as they are, a tiny
speck of dust is all it takes to either create an open connec-
tion or a noisy one.
5. Hazards
Ignoring the obvious High Voltage issues inside the power
supply (as you have no business opening the power supply
in the first place.) the greatest hazard to the technician is
fiberglass. Every circuit card in a computer is a laminate of
copper and fiberglass. The simple act of brushing against the
cut edge of a circuit card is enough to make some people
uncomfortable enough to require medical attention. If you are sensitive to fiberglass wear gloves whenever you will be
handling circuit cards.
6. Where to Begin?
The best place to begin is the Chassis. Start by installing the
I/O Back plate in the chassis and gently set the system board in place. If no stand off’s are installed, note the locations
where stand off’s will be required, remove the system board
and install the stand off’s. If the stand off’s are already
installed, verify that they line up with the mounting holes in
the system board. Remove any that do not line up with the
holes in the system board as they could “short circuit” the
components and circuit traces on the bottom of the board. If
they can be moved to locations where they can be used then
do so now. Not all mounting holes will have stand off’s
available. This is normal and will not lead to any problems.
Once all the mounts are prepared, remove the system board
and return it to it’s static bag.
With the system board mounting system ready, prepare the
chassis for the installation of the remaining components. If
System Board clearances allow, install the power supply,
hard disks and removable media drives at this time. Note:
unless there is a specific reason not to, be certain to address all IDE devices as cable select or “CS” via the addressing jumpers on the drive. Be certain that they will leave enough room to install the system board. Bundle all of the front panel cables together and tape them to a suitable location inside the chassis. You will not want to be fighting them while trying to install the system board. Repeat this step with the power cables.
Once again remove the system board from it’s static bag and
place it on top of the static bag. As a unit, gently set them on
the static mat. It is much easier to install the processor and
system memory with the system board outside of the chassis.
If there is a rigid mounting system for the processor cooling
complex install it now. Set the system board back on the
work surface and remove the processor from it’s box. Be sure
to leave the processor in it’s static protective package. Place
the processor (still inside of the static package) on the static
bag where it protrudes from underneath the system board.
This is an extremely important step as it electrically bonds
the processor to the system board indirectly via the static
packaging and brings both components to the same electrical
potential. Now lift the locking lever on the processor pad to
the full 90 vertical position. Locate the “pin 1” location on
the processor pad. It will always be marked. Look for a white
corner on the white id markings on the system board or an
area of textured plastic on one of the corners of the processor
pad. The processor will only fit in the correct position but the
pins are easily damaged and the act of setting and lifting is
enough to misalign some pins. Once pin 1 orientation is
achieved, very gently set the processor onto the pad. The pins
should easily drop into the holes of the pad. Once the body of the processor is seated against the top of the pad, lower the
locking lever to the “locked” position. This will be parallel
to the system board. Once the processor is in the locked
position, install the heat sink compound (if not pre-attached
to the cooling unit) to the top center of the processor and
install the cooling unit to the top of the processor. Make sure
the cooling unit is firmly pressed against the processor.
An improperly cooled processor will be damaged in a few
seconds of operation. Once the processor is fully installed,
repeat the un-packaging procedures with the system RAM.
Memory must be installed in accordance with the system
board manufacturers instructions regarding Banks, voltage
timing and size. Always consult the system board owners
manual prior to installing memory. Be certain to fill the
banks in the correct sequence with the correct type of
memory. If multiple memory modules can be installed in a
single bank, be certain that the modules are identical. Failure
to do so will result in problems with may prevent the system
from even powering up. Lastly, if your system board has any
configuration “Jumpers” or “switches” check the users manual and configure these setting now.
Once all memory and processors have been installed, move t the chassis to the static mat and bond the chassis to the
system board static bag. Once all components have been
bonded, gently install the system board in the chassis. Some
force will be required to “seat” the system board to the I/O
backing plate. This is normal and will not hurt the system
provided the backing plate is fully seated. While pressing
the system board against the backing plate the mounting
holes will come into line with the stand-offs. Install a couple
of securing screws but do not fully tighten them. The will
hold the system board in place while you set the remaining
screws. Once all of the mounting screws are set you may
tighten them. There is no need to “Torque” the system board
to the chassis. A “snug” tightening of the screws is all that is
required and excessive tightening may actually delaminate
the board resulting in premature failure. If the disk drives, removable media drives and/or power supply could not be installed prior to system board installation, do so now.
As a rule, adapter card installation is a very straightforward
affair with home computers. Video boards have dedicated
slots and other peripherals are not normally slot dependant.
Simply remove the blanking plate from the chassis and install the card. Some video boards will require separate power
connections or may take more than one expansion slot. If
you are only installing one or two boards besides the video
subsystem try to leave an open slot between each board to
allow for increased cooling.
Now that the system board, drives, power supply and adapter
cards have been installed, the “easy” part of system assembly
is over.
7. Cabling
When cabling a system one should always start with the
“front panel” cables. As more cables are installed the chassis
will become more cramped. As the chassis becomes more cramped the tiny connectors will become more and more difficult to install as they must be installed in the correct orientation. With this said I must now cover pin connector
orientation. All pin connectors should be keyed in some way
by the manufacturer i.e., some distinguishing mark to denote “Pin 1”. This is accomplished in many ways including, a red stripe along one edge of the cable, a missing pin, a cable marked with a specific color, a white dot, a white triangle on the white id of the board, plastic keys moulded into the cable end, or even the shape of the pin grid array of processors. This may seem very intimidating at first but it becomes intuitive rather quickly.
a)Front Panel Connections
Before you begin, look for a pattern in the cables. Usually they will each consist of two cables, one colored and one black. The colored cable will go to pin 1. On the system board, pin 1 will be denoted in the white id around the pins. Look for a pin that has more white ink below or beside it. This will be pin 1. (on occasion a “+” will be used.)
b)Fan Power Cables
Fan cables are generally keyed via the plastic connectors and can only be inserted in one way.
c)USB and other Ports
USB cables are predominately keyed via a missing pin. I one looks at the end of the cable there will be an un-used pin in the block which lines up with a missing pin on the board. This is not always true and in some cases the cables are loose and must be identified individually. I this case the system board manual must be used. Other I/O ports such as MIDI, Fire Wire, etc are usually of the keyed plastic type.
d)Disk Drives and Removable Media Drives
Disk drives as to say IDE drives have included a dizzying array of methods to denote pin 1. The keyed plastic being dominant but it’s rare to find an IDE cable without a Pin 1 stripe running the entire length of the cable. The missing pin method is also very common. This is where the “what if” game begins. What if there are multiple keys on one device? Will they be compatible? As a rule yes, but not always. In many cases the missing pin will be marked on the cable end by having “no” hole for the missing pin on the cable but the system board will use the keyed plastic jack and include the pin. If this condition is not caught prior to cable insertion the “extra” pin will be damaged and may short against a neighbor pin. You may find cables that do not include the key on the ends. This is simple. Look for the side of the connector with two slender grooves. (one at either end) this is the side that would have had the key. When all else fails, look at the cable and the system board. The side of the cable with the colored stripe is Pin 1 and the white id on the system board will always tell the pin 1 location. As for the drive end, on IDE disk drives pin 1 is always the side of the connector closest to the power connector. This is also true for CD-ROM and DVD drives. To decide which drive should be connected to which connector on the IDE cable, simply look for the end that will either be marked “system” or be colored blue. If neither end is marked in such a fashion the cable is probably an older type of IDE cable and should not be used as it will not handle “cable select” drive addressing or higher transfer speeds. The far end of the cable is drive 0 and the middle connector is drive 1. If “cable select” addressing is used it will make no difference and use the drive connector that is most convenient. On rare occasions the “cable select” method of addressing will not work and drives will have to be addressed manually. This will be covered in the troubleshooting section.