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Module 2 Highlights

Safe work areas are without food or drink and orderly with cables arranged out of the way.

Only experienced technicians should work on monitors or power supplies.

Power supplies, monitors and printers contain high voltage. Use the power supply intended for the device.

Unplug everything, remove jewlrey and loosen clothing before working on PC. Use tape to cover sharp edges inside case. Lift with knees and not back.

Be prepared for possible fire when working on PCS. Don't fight out of control fire and have planned escape route.

Extinguisher classes:

  • Class A: plastic, cardboard, wood, paper.
  • Class B: Flammable liquid (E.G. gasoline)
  • Class C: Electronics
  • Class D:combustable metals

Using Extinguisher (PASS)

  • (P)ull the pin.
  • (A)im at base of fire.
  • (S)queeze lever
  • (S)weep nozle back and forth.

Protect PC

ESD (electrostatic discharge) less than 30 volts can dammage components. It has to be 3,000 volts for human to notice, ten thousand volts of ESD makes a sound or causes human pain.

Precautions include:

  • Components remain inside anti-static bag until needed.
  • Use of grounded or antistatic mats.
  • Use of wrist straps.

EMI (electromagnetic interference) can travel a mile. Caused by things emiting electromagnetic field. Examples include motors, storms, power lines or solar radiation.

RFI: (radio frequency interference), affects wi-fi, caused by transmissions in the same frequency.

Hot climate can cause overheating; low humidity increases ESD; high humidity can cause moisture dammage.

Power problems

Power fluctuations result from unsteady voltage. Blackouts are a complete loss of power. Brownouts result with 80% voltage loss in a power line over an extended period. Noise is simply unclean power. Spikes and power surges are when voltage rises above 100% for a short period.

Lightning can cause noise, surges or spikes. Power line interference also causes noise. Overloading circuits causes brownouts. Dammaged transformers, down power lines or blown fuses cause blackouts. When power returns after blackout a spike can occur.

Difference between spike and surge: for the test, remember a spike is SUDDEN and DRAMATIC.

Surge suppressors divert extra voltage to ground, protecting against spikes and surges.

UPS (uninteruptable power supply) protects against power fluctuations. With its battery always topped off, there is a constant regulated voltage. Many UPS devices communicate with the OS, enabling orderly shutdown if power is off for long periods. Don't connect printer or other high-drain component to a UPS.

SPS (stand-by power supply) a backup battery providing DC to inverter which converts to AC. Cheaper than a UPS but less reliable because of the time needed to switch to the backup battery.

Hazardous materials (toxic waste) include heavy metals like lead, mercury or cadmium. MSDS (materials safety and data sheet) contains facts pertaining to each material, precautions, first aid, flamibility, chemical reactivity and disposal procedures. Consult MSDS to determine if a material is toxic.

OSHA regulates hazardous materials in the U.S. CHIP3 regulates them in the U.K. Both require the MSDS for all hazardous waste.

Safe disposal for each component must be considered when discarding a computer. Monitors can contain 4 pounds of lead; batteries contain mercury which is toxic to people. Toner and ink aerosol cans and chemical solvents must be disposed of following local environmental laws. A common fire extinguisher will actually fuel a chemical fire and distribute toxic fumes.

The right tool for the Job

ESD protection: anti-static wrist strap and anti-static mat.

Flathead screwdrivers loosen/tighten slotted screws. Philips-head screwdriver used for cross-headed screws. Torx screws have a star like depression on top. Hex driver loosens/tightens 6-sided (hexogonal) bolts. Hand tools also include flashlights, needle-nosed pliers, wire cutters, tweezers and part retrievers.

Soft cloth cleans components without leaving lint or scratching. Compressed air blows away dust. Cable ties keep wires neat. Parts organizer keeps components tech is working on orderly.

Digital multimeter tests integrety of signals/circuits and quality of power supplies. Loop-back connector resembles female DB25 to test basic functionality of ports.

Disk Management

  • FDisk or "disk management" -- partitions drive. Also can format partitions.
  • Format -- prepares drive to store files.
  • Chdsk or ScanDisk-- Detects and fixes problems with drive integrity. Scans file system and possibly disk surface for errors.
  • Defrag -- optimizes drive's space and speed.
  • Disk Cleanup -- Deletes files that can be safely removed.
  • SFC (system file checker) scans for OS integrity; replaces corrupted operating system files.

Windows XP boot disk can repair, restore, reinstall.

Fighting Malware

  • Windows security center: Checks status of windows update, ensures firewall and anti-virus are active.
  • Firewall protects against unauthorized access to the PC from the internet.
  • Spyware remover: deletes unauthorized programs that track you.
  • Virus Scanner: Protects against virus attacks


Tracking service and repairs is done with technician journals that should contain notes and service/repair history. Other personal documentation includes manuals, quick reference and troubleshooting guides.

On the internet, a technician can locate information through newsgroups and forums, manufacturer and general technical sites, online manuals and search engines.

Technicians can be creative; for example using masking tape to label components when a parts organizer is unavailable. In the field, a working computer is useful for researching.

An antistatic wrist strap equalizes the elecgtrical charge between the technician and equipment. Secure to unpainted metal, such as the fan grill, because the painted surface is a poor conductor. Wool, silk or polyester increases chance of ESD. An antistatic mat is slightly conductive drawing charge away from equipment.

Match screw to appropriate driver. Match hex driver to correct size nut. Clockwise tightens; counterclockwise loosens. Overtightening strips screws or bolts which could get stuck or fail to tighten. If component won't come loose, check for latch or clip holding it in place. Test if tool is magnetic by touching to a screw; if they're attracted, don't use that tool. Pencil lead is a conductor so don't use pencils inside PCS.

Excessive dust builds up heat acting as an unwanted insulator. But a standard vacuum cleaner has plastic parts that build up a dangerous static charge, so never use.

Blow dust with the nozzle of compressed air at least 4 inches from components. Clean fan and power supply from back of case. Don't let fan blades spin as it could ruin fan motor. Hold can right side up and Use short bursts of the compressed air.

Clean the outside of monitors and computer cases with a drop of dishwashing liquid dissolved in 4 ounces of water. Dip and wring out a lint-free cloth in to this mild cleaning solution. Use no glass cleaners or harsh chemicals on screens. Instead, use distilled water, and lint-free cloths to wash and fully wipe them dry.

Isopropyl, not rubbing alcohol should be used to clean contacts on components. Blow off any lint from cleaning before powering back up. A small hand-held vacuum cleaner with a brush attachment or compressed air can clean keyboards. Glass cleaner can be used on a mouse and its removable ball, but wipe with a soft cloth and don't spray cleaners directly on anything.

Lab 2.2.2 Hard Drive Diagnostics

Roll up your research sleeves and learn more about testing and troubleshooting drives. Researching information on the internet is an important tech skill and knowing about drive diagnostics helps you determine if a drive is truly failing.

Lab 2.2.3: Computer Disassembly

Your chance to take a real computer apart, or listen to the disassembly labs created by Grace as she assists local Cavi students and prepare your worksheet based on their disassembly experiences.

To find a real PC to take apart ask a local computer shop or amateur radio club. The PC does not need to be working. It's OK to get help from a more experienced friend.

Whether you do the lab from the recordings or using real hardware, read it all the way through first and note the questions it requires you to answer.

I took apart real hardware. I assembled all my tools first, and then put the lab on my Victor Reader Stream. This way I could read each step while I worked, and also use the Stream to note my answers.

---End Chapter 2.

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Page last modified on July 30, 2012, at 04:13 PM