Refurbishing Personal Computers

    A Beginner's Guide to Evaluating Donated Equipment

    If you know nothing about computer hardware, this guide is intended to give you a quick start in evaluating old computers. If is intended primarily for personal computers (PCs) of the 386, 486 and Pentium level, but much of the info here applies to even older machines (286 and XT level) as well.

    Dave Butler wrote this guide for volunteers working in computer reuse projects for community organizations in the Philadelphia area. This guide is freely distributed. You may use it and modify it as you wish.

    Quick Status Check

    When a batch of newly donated PCs arrives at our door, we first determine what works, and gather whatever info we can without opening the case. 

    The CPU

    By the way, we'll often refer to the case and its contents as a CPU, although technically the CPU, or central processing unit, is a matchbox-sized chip attached to the motherboard. In the first level or two of testing, we won't be opening the case. If and when you do, remember to detach the power cable while you're handling the components.

    I like to stand a row of CPUs on their sides, all facing the same way, so that I can test them in assembly-line fashion. When it's time for the next CPU, I'll move one plug at a time directly to its new spot and power up before I worry about moving the tested unit out of the lineup. The testing process is so slow that I'm often running several testing stations at once, each with a line of CPUs.

    The Monitor, a Lethal Weapon

    Out of its protective case, the monitor is a very hazardous piece of equipment. Unless you're more expert than I, you should NEVER mess with a monitor's innards. Even after sitting idle for several years, a cathode ray tube has a sufficient charge that, if cracked, it could send shrapnel flying at an uncomfortable speed.

    What's Written on the CPU?

    On the front of the CPU case you will usually find

    • Manufacturer's Name
    • Model Name

    On the back you will usually find

    • Serial Number

    On a sticker attached to the back you should find

    • our in-house Inventory ID number

    Label the Case

    Your test results you should record on the case. I prefer to place a small label on the back of the case, because the back is the only part of the case that is never separated from the contents. Unfortunately, because the back of the case usually doesn't offer much space for a label, you can't say very much unless you write very small. If there is free space on the inventory label, you could use that. Label the right side of the case if you can't find room on the back. If you have no labels, a china-marker works well on painted metal cases.

    Eyeball the Equipment

    • Does the model name indicate that the machine is of the 286 or XT level? Label these and set them aside. If we use these at all, we'll leave the analysis to the experts and students of antiquity! Grab another CPU and go back to What's Written on the CPU?
    • Is there a 3.5" wide floppy drive?
      • Many of the older machines we receive have only a 5.25" wide floppy. Label these as "Old" and set them aside. Grab another CPU and go back to What's Written on the CPU?
      • Some machines have both 3.5" and 5.25" floppy drives. These we will test.
    • What type of connectors are on the back (occasionally side or front) of the case? Many of them may be lined up along the bottom of the case where the motherboard sticks through the back of the case. This section is mostly for your information -- it's not necessary for you to record findings on your label.
      • Expect to find
        • Power connector
        • Keyboard connector, either a large 5-pin DIN or a small PS/2 type
        • Video or monitor connector, a narrow female plug with either 3 rows of holes or 2. If it's only 2, label as "Old" and set aside. Grab another CPU and back to What's Written on the CPU?
        • Parallel (printer) connector, a wide female plug with 25 holes
        • One or two serial (communication) connectors, narrow 9-pin male and/or wide 25-pin male
      • You may find
        • PS/2 mouse connector
        • extra parallel or serial connectors
      • If you notice the following, please indicate on your label:
        • NIC (network interface card)
        • sound card
        • modem

    Wire up the Equipment

    • Attach keyboard, either a large 5-pin DIN or a small PS/2 type, to CPU
    • Attach power cord to CPU
    • Attach power cord to a VGA monitor
    • Attach monitor data cable to CPU (the data plug has three rows of pins). If the CPU has no VGA plug (three rows of holes), label as "Not VGA" and set aside. If we use these at all, we'll leave the analysis to the experts. Grab another CPU and go back to What's Written on the CPU?

    Power On the Monitor

    • Power on the monitor.
    • Adjust the brightness and contrast only if you have trouble once the CPU is on.

    Insert Boot Disk

    • Insert into the 3.5" floppy drive a startup disk, labeled "DOS 6.22 Boot Disk." We usually use DOS version 6.22 for first-level testing of 386 and better equipment. On new 486 and Pentium equipment we might start with the DOS for Windows 95 (usually labeled "Win 95 Boot Disk").
    • "Boot disk" is a broadly defined term. Technically, it means any "system" diskette -- one which includes the "internal" core of the DOS operating system. A diskette is large enough to hold the core plus maybe a third of the "external" DOS commands. When we say "Boot Disk," we'll be referring to a system disk to which we've added a selection of external DOS commands, plus a few other files.

    Power On the CPU

    • Power on the CPU. Do you hear anything? If not, label "No Response" and set aside. Grab another CPU and go back to What's Written on the CPU?
    • Adjust the monitor brightness and contrast if you have trouble seeing the display.
    • You should see system startup messages appear on the screen.

    Power-On Self Test Begins

    • When you power on a PC, it first runs the Power-On Self Test (POST). This is a program which is permanently burned in on a Read-Only Memory (ROM) chip located on the system motherboard. It contains instructions which tells the system how to get started. The ROM chip, like a CD-ROM, does not require power to keep its data.

    Memory Check

    • The system's working memory is Random Access Memory (RAM). It uses chips which are erased when power is off. So every time the system is powered on, RAM starts with a clean slate.
    • Before the system begins using its RAM, it verifies that the chips are in working condition and counts their total number of bytes.
    • Most PCs display a counter on the screen while checking the main memory (RAM) area. Usually you'll see the counter stop at a certain number, then go back to zero and count up to the same number. This number is the total size of RAM in KB (kilobytes). Don't worry if this number disappears before you can make a note of it, as we'll be testing it again.
    • If the system gets stuck before you see a memory check, label "No RAM?" and set aside. Grab another CPU and go back to What's Written on the CPU?

    Basic Input-Output System (BIOS)

    • Next the POST checks your hardware connections, reading the hardware setup information that's stored on a chip called a Complimentary Metal Oxide Semiconductor (CMOS).
    • The setup information is known as the Basic Input-Output System (BIOS).
    • The CMOS is a special chip can retain a tiny amount of changeable data using only a tiny bit of power. So the PC is equipped with a low-powered battery, which should last for many years. One standard battery resembles a nickel, and costs about $2. Batteries come in a variety of shapes and sizes, depending upon the motherboard manufacturer.
    • The BIOS stored on the CMOS chip remembers the system date and time settings, as well as the location and specifications for hardware components such as hard drives, floppy drives, RAM, and boot drive sequence. Boot drive sequence is usually set to start the system from the A drive if a diskette is present, and to start from the C drive if not.

    System Setup Errors

    • The POST verifies that all the hardware listed in the BIOS is present and working.
    • If the POST finds that the hardware is different from what's listed in the BIOS, it will display an error code. The code may be accompanied by an explanation. Note on your label "Error" and add the error code(s). Add an explanation if available. You can find an explanation of error codes in an invaluable reference book called Guide to Maintaining and Repairing PCs(?).
    • Upon finding an error the POST may or may not allow you to continue:
      • Some POST programs will prompt you to press F1 to bypass the error. Try bypassing the error by pressing F1. If the system still won't proceed, set aside. Grab another CPU and go back to What's Written on the CPU?
      • IBM Personal System 2 (PS/2) machines may display an icon which indicates that you should insert a Reference Disk. Note on your label "Needs Ref Disk." Try bypassing the error by pressing F1. If the system still won't proceed, set aside. Grab another CPU and go back to What's Written on the CPU?

    Power-On Self Test Completes

    • ...

    Starting MS-DOS

    • ...

    Date and Time Check

    • If the system starts normally from 3.5" diskette, you will be prompted to verify the date. Key in the correct date, or just press Enter if the date is correct. Verify the time.
    • The DOS prompt A:\> should appear. If not, go to A: Drive Doesn't Boot

    Yes! System Boots from 3.5" A: Drive

    • Record on your label "A: boots"
    • Type MSD and press Enter
    • Record the following on your label:
      • Memory or RAM in rounded megabytes (MB). Example: 4096 bytes = 4MB
    • Press D for Drive details:
      • Record hard drive size in rounded megabytes (MB).

    Congratulations! You're Done!

    • Power off the CPU. Now hurry up and move all your cables to the next CPU and power it on. This is your only chance to save a little time! The rest of the testing process is an exercise in waiting. Go back to What's Written on the CPU?

    A: Drive Doesn't Boot

    • Okay! Don't panic! Take a deep breath.

    So What's Happening?

    • The system displays the message, "Starting MS-DOS" but then boots to the C:\> DOS prompt, rather than the A:\> prompt.
    • The system displays the message, "Starting MS-DOS" but then seems to get stuck.

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    This page written by Dave Butler, Computer Guide
    dbut@erols.com


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