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Safe Working Procedures and General Maintenance

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This lesson takes approximately 1 hour to complete.


Practice ESD damage prevention

List the basic equipment needed to reduce the risk of damage from ESD and explain how this equipment works

Set up a conductive workbench mat

Identify the risks of working with CRTs

Locate CRT safety, discharge, and disposal procedures

State the eight CRT safety rules

Discharge a CRT using Apple-recommended procedures

Explain safety and first-aid procedures related to the leaking of liquid coolant

Describe the hazards of working with an iMac power supply

Describe the risks of booting into EFI

Care for the translucent plastics on Apple products

Clean and maintain a monitor screen

Back up files

Check for viruses

Dispose of batteries safely

Optimize a hard disk

Whether the computers you’re taking care of belong to you, a customer, or a large group, this lesson provides the information you need to approach any situation safely and with the proper tools.

In this lesson, you will learn about the risks to you and the computer when you service computers, as well as general maintenance tasks you might perform during the “verify repair” step in the Apple General Troubleshooting Flowchart. While these may seem like unrelated topics, safe workstations and conscientious work practices are all part of keeping computers, customers, and yourself happy.

ESD Prevention

Whenever you open a Macintosh or other electrical device, you are exposing its internal components to potential damage from the static electricity that builds up in your body through normal activity. Electrostatic discharge (ESD) occurs when static electricity is discharged from one conductor (such as your finger) to another conductor (such as a memory chip) of a different potential. Exposing an integrated circuit (IC) to as little as 10 volts of static electricity can damage the IC irreparably—and you wouldn’t even know it happened, because humans can’t perceive static electricity less than 1500 volts. When you do feel an electrical shock, you are feeling a minimum of 3000 volts.

Since imperceptible ESD can damage ICs found in computer and communications equipment, you must be particularly careful when working on Macintosh hardware. Plastics, utensils, polystyrene products, polyester clothing, and even the ungrounded touch of your hand carry sufficient electrostatic charges to damage electronic components, even if you don’t feel a spark. This section provides guidelines for preventing ESD damage and describes how to set up an ESD-compliant workstation.

ESD Safety Guidelines

Follow these guidelines to reduce the risk of ESD damage:

  • Before working on any device containing a printed circuit, ground yourself and the equipment you are working on to an earth or building ground. Use a grounded conductive workbench mat and a grounding wrist strap or heel strap, and ground the equipment to the mat.
  • Handle all ICs by the body, not by the pins. Do not touch the edge connectors, exposed circuitry, or printed circuits on boards or cards. Handle ICs, boards, and cards by the edges, or extract them using an ESD-compliant pair of pliers or other appropriate tool.
  • Never place components on any metal surface. Metal surfaces can hold a static charge that will damage sensitive electronic parts. Use antistatic, conductive, or foam rubber mats.
  • Do not touch anyone who is working on ICs. If you touch someone who is properly grounded, your “zap,” or body charge, might cause damage. Always keep your own body charge away from other technicians.
  • Use static-shielding storage bags for boards and ICs. Before you leave your bench to take a board to a storage place, put the board in a static-shielding bag. Leave all Apple replacement modules in their ESD-compliant packaging until you need them.
  • Don’t wear polyester clothing or bring plastic, vinyl, or Styrofoam into the work environment. The electrostatic field that surrounds these non-conductors cannot be totally removed without the use of an ionized air generator.
  • If possible, keep the humidity in the service area between 70 and 90 percent, and use an ionized air generator if available. Charge levels are reduced (but not eliminated) in high-humidity environments. Using an ionized air generator helps neutralize the charge surrounding nonconductors. However, this type of device can’t provide total protection: the static charges often cause ESD damage before the neutralizing process eliminates the charge.

Workstation Setup

Before you start to work on any task involving circuit boards, you must verify that your workstation is ESD-compliant—that is, that it has equipment and materials designed to prevent ESD damage.

You need the following equipment to set up an ESD-compliant workstation:

  • A conductive workbench mat and wire lead—When properly grounded, the workbench mat provides a safe place on which to set sensitive components and equipment.
  • A wrist strap with a built-in 1-megohm resistor and wire lead—The wrist strap grounds you so that you can touch sensitive components without zapping them.
  • An equipment wire lead with alligator clips—This wire lead grounds the equipment so that an electrostatic charge cannot build up. It is especially important when you are working on CRTs, which can build up an electrostatic charge even when they are not plugged in.
  • A ground/polarity tester—This tester verifies proper grounding of power outlets.

A Note on Working Off-Site

When you work at a customer site, you must take the same precautions to avoid ESD damage. Take time to make the work area ESD-compliant. Take a workbench mat and a wrist strap with you. (For travel convenience, you may want to use a mat that folds up.) Be sure everything is properly grounded and never set parts on the floor.

ESD-Compliant Workstation Quiz

Read Knowledge Base document 50077, “ESD Prevention Rules”, and answer the following questions:

  1. When there is a risk of contacting high voltage, such as when you discharge a CRT or work with a powered-on CRT, do you wear a grounding wrist strap?
  2. When there is a risk of contacting high voltage, do you work on a grounded pad?
  3. What items do you need to set up an ESD-compliant workstation?
  4. For what do you use a ground/polarity tester?

Answer Key

1. No; 2. No; 3. A conductive workbench mat, a wrist strap with 1-megohm resistor and ground cord, a wire lead with alligator clips, and a ground/polarity tester; 4. To verify proper grounding of the power outlet.

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