ACTUAL BASIC ELECTRONIC COMPONENENT TESTS USING ANALOG MULTI-TESTER

WARNING:

When testing any form of electronic equipment there are several precautions you must take.

1.    Make sure the equipment is disconnected from any form of power supply,.

2.    Be aware that the devices contain components which can hold enough electrical current to stop a human heart.

3.    Electrical current can damage your testing equipment when used improperly.

4.    Make sure that your testing equipment is the correct equipment for the job.

5.    Removed electronic components to be tested from the circuit board in testing resistance.

Testing resistors

1.    Read the indicated (color code) value on the resistor.

2.    Calibrate the ohmmeter.

3.    Set the tester to ohmmeter range depending on the resistance value.

4.    Place the test probe to the two terminal lead of the resistor.

Good resistor- the meter should be close to the rated value of the resistor depending on the tolerance of the resistor.

Defective resistor

 -tester pointer does not deflect at all, resistor is OPEN.

-the resistance reading has big difference to the resistor rated value, resistor is OUT OF TOLERANCE.

-zero resistance reading at all OHM scale, resistor is SHORTED.

Testing Capacitor

1.    Discharge the energy stored to capacitor by shorting the two terminal lead momentarily.

2.    Set the tester ohmmeter range.

Capacitance                                                 Range

0.01uF to 1uF                                              x10k

1uF to 47uF                                                 x1k

47uF to 1000uF                                            x10

1000uF and above                                        x1

3.    Connect the positive probe to the capacitor negative lead and the negative probe to capacitor positive lead.

Good Capacitor- the pointer will deflect towards zero and move back again to the infinite resistance position.

Defective Capacitor

-      Tester pointer won’t deflect at all, capacitor is OPEN.

-      Tester pointer will rest on the 0 ohm scale, capacitor is SHORTED.

-      Tester pointer deflects toward the right position but does not return to its initial position, capacitor is LEAKY.

Testing potentiometer

1.    Set the ohmmeter range to appropriate settings.

2.    Connect the probes in the exterior terminals of the potentiometer.

3.    Rotate the shaft fully clockwise. The pointer should be at the highest resistance reading.

4.    Slowly rotate the shaft counter clockwise, the resistance reading should gradually fall to zero.

Defective potentiometer

-      Tester pointer won’t deflect at all, potentiometer is OPEN.

-      Tester pointer suddenly deflects in gradual adjustment, wiper contact is already DEFECTIVE.

Testing Diode

1.    Set the ohmmeter in x1 or x10.

2.    Connect the positive probe to the anode and the com probe to the cathode.

3.    Reverse the test probe, the tester should deflect but not rest at zero ohm.

Good Diode- the tester pointer should deflect t very little or may not deflect at all.

Defective Diode

- Tester pointer won’t deflect even the probe is reverse, diode is OPEN.

-Resistance reading deflects and measures the same in both directions, diode is SHORTED.

Testing  Transistor- determining if transistor is NPN or PNP.

1.    Determine the correct terminals of the transistor.

2.    Set the tester to the x1 or x10 ohm range.

3.    Connect the positive probe of the meter to the emitter and the com probe to the base of the transistor. Note the reading. Emitter to base – less than 150 ohms, base to emitter – infinity. = NPN

4.    Interchange the connection of the probes to the leads of the transistor. Note the reading. Emitter to base – infinity, base to emitter – less than 150 ohm = PNP

Defective transistor

-      Two terminals of the transistor reads the same resistance (almost zero ohm) in both direction, Transistor overheat during normal operating condition except power transistor, transistor is SHORTED.

-      Tester pointer does not deflect in base to emitter or base to collector, transistor is OPEN.

Testing transformer

1.    A transformer is checked for continuity just like wire.

2.    Attached the test probe (any direction) to the terminal s of the primary transformer. Pointer should be deflecting.

3.     Attached the test probe (any direction) to the terminal s of the secondary transformer. Pointer should be deflecting.

Defective transformer

           

-      The resistance of the primary or secondary windings is very low that the pointer almost rest at zero ohm, the transformer winding is SHORTED.

-      The resistance of the primary or secondary windings is very high that the pointer does not deflect at all (infinite resistance) , the transformer winding is OPEN.,

Testing fuse with an ohmmeter

1.    A good fuse has practically zero resistance, when measured with an ohmmeter.

2.    To check the fuse with an ohmmeter, turn the power “off” or remove the fuse from the circuit.

3.    A blown fuse is open, which reads infinite on the ohmmeter.

With a voltmeter

1.    A fuse can be checked with the power “on” in the circuit by using a dc or ac voltmeter.

2.    A good fuse has zero volt across its two terminals, because there is no voltage drop.

3.    If the fuse is burned open, the voltmeter reading is equal to other voltage  source.

Testing the switch with an ohmmeter

1.    When closed (“on” position), a good switch has practically zero resistance.

2.    With an open or defective switch (or “of” position) the resistance is high or infinite and no current flows in the circuit.

3.    To check the switch with an ohmmeter, unplug the entire unit from the power source or remove the switch from the circuit.

1.    When the switch is open (“off” position), the entire circuit is turned off, even the switch is connected in just one side on the line.

With a voltmeter.

1.    A switch can be checked with the power “on” in the circuit by using a DC or AC voltmeter as the case maybe.

2.    When closed (“on” position), a good switch has zero volt across its two terminals, because there is no voltage drop.

3.    If the switch is open (“off” position) or defective, the voltmeter reading is equal to the voltage source.