Safety Considerations In Troubleshooting
In working with electrical and electronic devices, safety can never be overly emphasized. No matter how experienced or competent you are as a troubleshooter, you must always respect the power of electricity and follow proper safety considerations. Electricity can cause significant damage to the human body ranging from small burns to the skin, neurological and muscle damage, to death. The combination of voltage and amperage that actually flows through your body is what causes damage. It is possible that a high amount of voltage can zap your hand away from the power source and cause little harm, but a small amount of voltage with a high amount of current can actually kill you. The possible extent of damage by a particular combination of voltage and amperage also depends on the amount of resistance of the body.
For example, when current flows through a person’s body the heart and lungs can be interrupted and cause temporary or permanent effects. Suffocation can result when a person is unable to breathe. When the heart is impacted, it can stop pumping blood and the natural rhythm of the heart can be disrupted. In this case, death may be imminent. One common condition is called ventricular fibrillation, which causes a disruption of the heart’s natural muscle rhythm and makes the muscle contract rapidly and randomly. This condition is typical of victims who experience household deaths as a result of the person’s heart triggering into fibrillation.
Electricity can cause physiological effects to the body with as little as 100 milliamperes (mA) of current when applied directly to a person’s heart. Body injury can result to muscles due to involuntary muscle contractions with as little as 5 to 10 mA of current. Current above 100 mA can cause muscle paralysis, breathing disruption, skin burns, and possible ventricular fibrillation and death.
Safety Considerations In Troubleshooting
Therefore, before servicing any electrical device, it is critical that any troubleshooter carefully read the service manual and supplements. Some general considerations include the following:
- Ensure that the electrical power has been removed from the device.
- Always ensure the correct polarity of any installation of any component, especially electrolytic capacitors. The incorrect installation can actually cause the device to explode.
- Caution should be taken not to use any spray chemicals near the electronic device.
- Follow the service manual recommendations for cleaning electrical contacts by using only solutions suitable for the device. For example, 90 percent isopropyl alcohol is often recommended for electronic contacts or acetone with application using a pipe clearer or a cotton swab or comparable nonabrasive applicator. However, caution should be taken since this material can be flammable.
- Never test a high voltage by drawing an arch.
- Always use a suitable high-voltage test meter such as a digital voltmeter (DVM) or Fetvom with a high-voltage probe attachment.
- When servicing devices, use proper ground lead from the chassis ground and remove the test receiver ground lead first when completed.
- When soldering, use a grounded-tip low-wattage soldering iron.
- Always keep the soldering iron tip clean and well tinned.
- Avoid overheating electronic components when soldering.
- Develop a skill of moving quickly when touching the iron tip to the junction of a component lead or printed circuit board and only as long as needed for the solder to flow.
A special caution should be advised for electrostatically sensitive devices. Most semiconductor devices can be easily damaged due to electrostaticity. Typical examples of these components include Fet transistors, Mosfet transistors, and ICs. When unpacking semiconductor components, be sure to avoid any electrostatic charges to your body by maintaining a connection to earth ground. You should generally wear a commercially developed grounding strap that helps prevent electrostatic buildup in the body.
Moreover when possible, use antistatic solder and minimize any motion when unpackaging electronic components that might harm the devices by generating electrostaticity. Also, use antistatic mats on the floor and other commercially produced antistatic products. Also, you should be careful not to work on electronic devices on carpet since this can produce an electrostatic charge. Some popular antistatic devices include a wrist strap and ground bracelet. These devices help keep you grounded and prevent the development of electrostatic charges within the body. These antistatic devices allow for voltage charges to leak through to the ground and prevent static buildup.
Besides the wrist and bracelet straps, the use of ankle and heal antistatic straps are common and operate in the same manner. These straps are particularly useful when people need to be mobile in a work area in which the buildup of voltage can be discharged through a special floor material. More expensive wireless straps are available. Besides damage to electronic devices, proper antigrounding devices should always be used where combustible, flammable, and explosive materials are present.
For example, when a novice works on a personal computer, he or she avoids using antistatic straps when replacing the random access memory (RAM) module, which is a common mistake. Three thousand or more volts can actually be produced through static electricity before you can feel it, especially in low humidity environments. Therefore, replacing a RAM module or other IC in a computer could cause damage by as little as 300 to 400 volts (V).
Moreover, when a RAM module is damaged, it is often hard to diagnose, especially if you just inserted a brand new one. The last thing the novice troubleshooter may think is that it was damaged because of static electricity and may be more apt to blame the manufacturer. Therefore, never be penny-wise and pound-foolish.
Keep in mind that just because you have utilized a ground to the electrical ground in a home or office does not mean that the ground is satisfactorily working. It is possible, especially in older homes, that the outlets are not even properly grounded or grounded at all. Therefore, the best recommendation is to use an antistatic wrist strap and antistatic floor pad. Remember to also keep any unneeded devices, such as telephones, away from the computer since the touching of them to the computer may cause static electricity as well.