Cuyamaca College
Department of Computer and Information Sciences
CIS-120 Computer Maintenance/A+ Certification
Lab 3--Testing Power Supplies
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A. Purpose of this Lab. The purpose of this lab is to give you experience using a multimeter to measure the various voltages delivered by a power supply. At the end of this lab you should be able to:
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Understand the various functions of a multimeter.
Know how to set the multimeter to test DC voltages.
Know how to use multimeter probes.
Know how to measure various voltages delivered by the power supply.
Understand safety considerations when working around electricity.

B. Cautions.
1. Remember--electrostatic discharge is a major concern while working on computers. Make sure you are properly grounded before touching any component. Consequently, do not use a grounding strap when working around a power supply.
2. Ensure the computer is in working order before performing tests.
3. Make sure your multimeter is set to measure the appropriate type and levels of voltage you expect. 4. Only touch the components necessary to take the required measurements.
C. Procedure. The following procedure applies to our lab computers. All computers are similar but may have different components, component placement, and external case designs.
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Power up the computer to make sure it is in working order.
Power the computer down and wait for the disk drive to stop spinning.
Take the top and side case off of the computer.
Turn the computer on its side to expose interior components.
Insert the supplied red and black probes as follows:
a. Red probe into the “+” or positive jack.
b. Black probe into the “-“ or negative jack.
6. Turn on the multimeter.
7. Make sure the multimeter is set to measure DC voltages and that the voltage recording range is set to measure down to one-tenth of a volt.
8. Turn on the computer.
9. Measure each circuit by placing the black probe in the pin indicated in the diagram below and the red probe in the pin indicated.
10. Record the voltage indicated in the appropriate area of the diagram below.
11. Ensure each member of the group has the opportunity to measure circuits.
12. When you have completed the table reassemble the computer.
13. Power up the PC to make sure it works.
D. Record Results. Using the