Troubleshooting Transistors 2qd44
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Instructions 1. Testing a Diode o
1
Set the control dial on your multimeter to the "diode" setting. Most digital multimeters have a diode test setting indicated by the schematic symbol for a diode, which is an arrow pointing at a line. o
2
Connect the red test lead of the multimeter to the anode of the diode, and the black lead to the cathode. The cathode end of a diode is indicated by a band on the case. If the diode is working, the meter will display the forward voltage, often about 0.7 volts. o o
3 Reverse the test leads. The meter should read "OL," indicating an open circuit. Any other reading means the diode has failed.
2. Testing a Transistor o
4
Set your meter to "diode" mode. o
5
Connect the red lead to the base of the transistor and the black lead to the emitter. If it's an NPN transistor, the meter should show the forward voltage drop of the transistor, usually a value between about 0.5 and 1 volt. With a PNP transistor, the meter should read "OL," indicating an open circuit. An open circuit means that there's no electrical connection. o
6
Switch the black test lead to the collector and leave the red lead connected to the base. The readings should be identical to the previous test. o
7
Reverse the test leads so that the red lead is connected to the collector and the black lead is connected to the base of the transistor. The readings should be the reverse of the previous test. o
8
Connect the red test lead to the emitter of the transistor, with the black test lead still connected to the base. If it's an NPN transistor, the meter should read that it's an open circuit. If you're testing a PNP transistor, the meter should show the forward voltage drop. o
9 Connect one of the test leads to the collector of the transistor and the other to the emitter. It doesn't matter which lead you connect to which. The meter should indicate an open circuit.
How to Determine the Base of Transistor With the Use of Multi Tester By David Sandoval, eHow Contributor
Print this article
You can use a multimeter or multitester to check a transistor.
A bipolar junction transistor is made up of three semiconductor regions. Each region contains a specific impurity that has been introduced into the semiconductor material. These regions are called "p-regions" or "n-regions" depending upon the dopant.
For a bipolar junction transistor to conduct electrical current, it must have its emitter and collector regions contain the same type of dopant. Therefore, an "NPN" transistor has its collector and emitter terminals doped as "n-regions" whereas the base terminal is doped as a "p-region." You can find the base terminal on an unmarked bipolar junction transistor by using the diode-check function on a digital multimeter or multitester.
Bipolar junction transistor
Multitester or digital multimeter with diode-check function
Instructions 1. o
1 Turn on the multitester or multimeter, and set the scale for "Diode Test."
o
2
Connect the red probe from the multitester or multimeter to the center lead on the transistor. Connect the black probe to the lead on one of the edges of the transistor. o
3 Check the multimeter or multitester display. If the display shows that the circuit ed a diode test, this indicates that the red probe is connected to the base lead and no further testing is necessary. Should the diode test fail, remove the black probe from the lead on the edge of the transistor. Attach this probe to the transistor lead on the opposite edge of the transistor.
o
4 Check the multimeter or multitester display. If the display shows that the circuit ed a diode test, this indicates that the red probe is connected to the base lead and no further testing is necessary. If the diode test fails, detach the black probe from the lead on the edge of the transistor and place this probe on the center lead. Place the red probe on one of the leads on one of the edges of the transistor.
o
5
Check the multimeter or multitester display. If the display shows that the circuit ed a diode test, this indicates that the red probe is connected to the base lead and no further testing is necessary. If the diode test fails, detach the black probe from the center lead and place this probe on the edge lead opposite the red probe. o
6
Check the multimeter or multitester display. If the display shows that the circuit ed the diode test, this indicates that the red probe is connected to the base lead. If the circuit does not the diode test, the transistor is faulty and should be disposed of promptly.
How to Test Transistors in a Circuit
How to Test Transistors in a Circuit
An electronic transistor is essentially two diodes. Diodes and transistors are either in service or not since neither are known to wear out gradually. Any component that goes bad in a circuit can prevent it from functioning. Transistors perform an important duty in circuits, and if they are shorted out or open they will cause the circuit to fail. Test the transistors in faulty electronics to find out if problems can be fixed by replacing them.
Things You'll Need
Insulated screwdriver
Ohmmeter or digital multimeter
Solder iron
Instructions 1. o
1
Turn off the power to the circuit before testing. Unplug the AC power cord and/or remove the battery supplying power. Exhaust power from all capacitors on the board. Touch both the terminals on a capacitor simultaneously with a metal screwdriver that has an insulated handle to cancel out the stored power. o
2 Identify the base, collector, and emitter leads on a transistor. The leads may be labeled B, E, and C or the orientation within the circuit may reveal which lead is which. Consult an electronics supplier catalog for exact orientation of the leads on particular transistors if no positive identification is present.
o
3 Set a digital multimeter to a diode setting if it has one; use an ohms setting otherwise. Use a low ohms scale setting on analog meters.
o
4
Check the base to collector readings in both directions. Touch one lead from the meter to the base lead and the other to the collector lead. Look at the reading, then reverse the leads. A good reading will show infinity in one direction and give a reading of about 600 in the other. o
5
Check the base to emitter readings in both directions. Touch one lead to the base and the other to the emitter. Check the meter and reverse the leads to read the opposite direction. Good readings should show infinity in one direction and close to 600 in the other. o
6
Remove the base lead if the numeric readings are far from 600. Other electronic components like resistors may affect the readings from a transistor within a circuit. Use a soldering iron to melt the solder holding the base lead of the transistor to the circuit board and pull the base lead out of the board so it's not connected to the circuit. Then use the meter to test both directions from base to collector and base to emitter again. Use the solder iron to melt the solder over the hole the base lead occupied and push the base lead back into that hole in the board after taking meter readings. o
7 Replace a transistor if either the base to emitter or base to collector readings show zero in both directions or infinity in both directions. Zeros reveal a short while infinities indicate an open diode within the transistor.
How to Test a Transistor With an Ohm Meter Used to amplify a current, a transistor consist of two diodes wired together in parallel. A transistor is either an NPN transistor, which has one input and two outputs, or a PNP transistor that has two inputs and one output. Both styles of transistor have three leads known as the collector (C), base (B), and emitter (E). A transistor can quickly and easily be checked with an ohmmeter to insure proper functioning. Most digital multimeters also have a setting to measure resistance that will perform the same function. Knowing the type of transistor and location of its leads is important when performing this type of test.
Instructions 1. o
1 Identify the type of transistor you are working with and the location of each lead. The style and location of the leads should be identified on the transistor packaging.
o
2
Set your ohmmeter to measure resistance in the low ohms range, around 10 ohms. o o
3 Touch the red meter probe to B, and the black probe to C for an NPN transistor. Touch the black probe to B and the red probe to C for a PNP transistor.
o
4
Observe the display. Note the reading on the display, which will either be zero or some other number above zero (the exact number is not important). o
5 Repeat steps 3-4 keeping the probe connected to B in the same manner, but connecting the second probe to E. If either or both the connections from B to C and B to E read zero, the transistor is bad.
1
Set the control dial on your multimeter to the "diode" setting. Most digital multimeters have a diode test setting indicated by the schematic symbol for a diode, which is an arrow pointing at a line. o
2
Connect the red test lead of the multimeter to the anode of the diode, and the black lead to the cathode. The cathode end of a diode is indicated by a band on the case. If the diode is working, the meter will display the forward voltage, often about 0.7 volts. o o
3 Reverse the test leads. The meter should read "OL," indicating an open circuit. Any other reading means the diode has failed.
2. Testing a Transistor o
4
Set your meter to "diode" mode. o
5
Connect the red lead to the base of the transistor and the black lead to the emitter. If it's an NPN transistor, the meter should show the forward voltage drop of the transistor, usually a value between about 0.5 and 1 volt. With a PNP transistor, the meter should read "OL," indicating an open circuit. An open circuit means that there's no electrical connection. o
6
Switch the black test lead to the collector and leave the red lead connected to the base. The readings should be identical to the previous test. o
7
Reverse the test leads so that the red lead is connected to the collector and the black lead is connected to the base of the transistor. The readings should be the reverse of the previous test. o
8
Connect the red test lead to the emitter of the transistor, with the black test lead still connected to the base. If it's an NPN transistor, the meter should read that it's an open circuit. If you're testing a PNP transistor, the meter should show the forward voltage drop. o
9 Connect one of the test leads to the collector of the transistor and the other to the emitter. It doesn't matter which lead you connect to which. The meter should indicate an open circuit.
How to Determine the Base of Transistor With the Use of Multi Tester By David Sandoval, eHow Contributor
Print this article
You can use a multimeter or multitester to check a transistor.
A bipolar junction transistor is made up of three semiconductor regions. Each region contains a specific impurity that has been introduced into the semiconductor material. These regions are called "p-regions" or "n-regions" depending upon the dopant.
For a bipolar junction transistor to conduct electrical current, it must have its emitter and collector regions contain the same type of dopant. Therefore, an "NPN" transistor has its collector and emitter terminals doped as "n-regions" whereas the base terminal is doped as a "p-region." You can find the base terminal on an unmarked bipolar junction transistor by using the diode-check function on a digital multimeter or multitester.
Bipolar junction transistor
Multitester or digital multimeter with diode-check function
Instructions 1. o
1 Turn on the multitester or multimeter, and set the scale for "Diode Test."
o
2
Connect the red probe from the multitester or multimeter to the center lead on the transistor. Connect the black probe to the lead on one of the edges of the transistor. o
3 Check the multimeter or multitester display. If the display shows that the circuit ed a diode test, this indicates that the red probe is connected to the base lead and no further testing is necessary. Should the diode test fail, remove the black probe from the lead on the edge of the transistor. Attach this probe to the transistor lead on the opposite edge of the transistor.
o
4 Check the multimeter or multitester display. If the display shows that the circuit ed a diode test, this indicates that the red probe is connected to the base lead and no further testing is necessary. If the diode test fails, detach the black probe from the lead on the edge of the transistor and place this probe on the center lead. Place the red probe on one of the leads on one of the edges of the transistor.
o
5
Check the multimeter or multitester display. If the display shows that the circuit ed a diode test, this indicates that the red probe is connected to the base lead and no further testing is necessary. If the diode test fails, detach the black probe from the center lead and place this probe on the edge lead opposite the red probe. o
6
Check the multimeter or multitester display. If the display shows that the circuit ed the diode test, this indicates that the red probe is connected to the base lead. If the circuit does not the diode test, the transistor is faulty and should be disposed of promptly.
How to Test Transistors in a Circuit
How to Test Transistors in a Circuit
An electronic transistor is essentially two diodes. Diodes and transistors are either in service or not since neither are known to wear out gradually. Any component that goes bad in a circuit can prevent it from functioning. Transistors perform an important duty in circuits, and if they are shorted out or open they will cause the circuit to fail. Test the transistors in faulty electronics to find out if problems can be fixed by replacing them.
Things You'll Need
Insulated screwdriver
Ohmmeter or digital multimeter
Solder iron
Instructions 1. o
1
Turn off the power to the circuit before testing. Unplug the AC power cord and/or remove the battery supplying power. Exhaust power from all capacitors on the board. Touch both the terminals on a capacitor simultaneously with a metal screwdriver that has an insulated handle to cancel out the stored power. o
2 Identify the base, collector, and emitter leads on a transistor. The leads may be labeled B, E, and C or the orientation within the circuit may reveal which lead is which. Consult an electronics supplier catalog for exact orientation of the leads on particular transistors if no positive identification is present.
o
3 Set a digital multimeter to a diode setting if it has one; use an ohms setting otherwise. Use a low ohms scale setting on analog meters.
o
4
Check the base to collector readings in both directions. Touch one lead from the meter to the base lead and the other to the collector lead. Look at the reading, then reverse the leads. A good reading will show infinity in one direction and give a reading of about 600 in the other. o
5
Check the base to emitter readings in both directions. Touch one lead to the base and the other to the emitter. Check the meter and reverse the leads to read the opposite direction. Good readings should show infinity in one direction and close to 600 in the other. o
6
Remove the base lead if the numeric readings are far from 600. Other electronic components like resistors may affect the readings from a transistor within a circuit. Use a soldering iron to melt the solder holding the base lead of the transistor to the circuit board and pull the base lead out of the board so it's not connected to the circuit. Then use the meter to test both directions from base to collector and base to emitter again. Use the solder iron to melt the solder over the hole the base lead occupied and push the base lead back into that hole in the board after taking meter readings. o
7 Replace a transistor if either the base to emitter or base to collector readings show zero in both directions or infinity in both directions. Zeros reveal a short while infinities indicate an open diode within the transistor.
How to Test a Transistor With an Ohm Meter Used to amplify a current, a transistor consist of two diodes wired together in parallel. A transistor is either an NPN transistor, which has one input and two outputs, or a PNP transistor that has two inputs and one output. Both styles of transistor have three leads known as the collector (C), base (B), and emitter (E). A transistor can quickly and easily be checked with an ohmmeter to insure proper functioning. Most digital multimeters also have a setting to measure resistance that will perform the same function. Knowing the type of transistor and location of its leads is important when performing this type of test.
Instructions 1. o
1 Identify the type of transistor you are working with and the location of each lead. The style and location of the leads should be identified on the transistor packaging.
o
2
Set your ohmmeter to measure resistance in the low ohms range, around 10 ohms. o o
3 Touch the red meter probe to B, and the black probe to C for an NPN transistor. Touch the black probe to B and the red probe to C for a PNP transistor.
o
4
Observe the display. Note the reading on the display, which will either be zero or some other number above zero (the exact number is not important). o
5 Repeat steps 3-4 keeping the probe connected to B in the same manner, but connecting the second probe to E. If either or both the connections from B to C and B to E read zero, the transistor is bad.
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