HOW TO TEST ICs Chips VOLTAGE REGULATOR
IC VOLTAGE REGULATOR TESTING / test integrated circuit
IC Voltage Regulator part number 78XX 79XX series are popular ICs that use on many power supply circuit. Regulate voltage function is necessary for every electronic circuits so we always find these ICs on many circuits , The ICs is small and has many package to choose. The basic package is TO-220 and TO-3 as shown on photo below. 78XX series is for positive output for part number example 7805 = 5VDC , 7812 = 12VDC , 7815 = 15VDC etc. 79XX series is for negative output for part number example 7 905 = - 5VDC , 7912 = -12VDC , 7915 = -15VDC etc. The part number has L at the middle like 78L05 , 78L12 , 78L15 means it has output current around 100mA and part number has T at end like 7805T , 7812T , 7815T
mean it has output current around 1A. Every electronic learner can check good or bad ICs so he can repair circuit. Before checking the ICs , you need to know it's pinning function . 78XX series and 79XX series has different pinning arrangement. If you are working with circuit repairing , It is good that you can remember the pinning as shown below.
This package is TO-220 ( TO = Transistor Outline ).
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| This package is TO-3 |
For 78XX series ICs , pin number 1 is input , Pin number 2 is Ground and Pin Number 3 is Output. If you can not remember that information , you can check it with datasheet. If you do that pinning checking for 2 or more times then you will automatically remember.
For 79XX series ICs ( front View ) , pin number 1 is Ground , pin number 2 is input and Pin number 3 is output .
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| Front View for 79XX series terminals. |
For TO-92 78XX series ICs. ( front view ) you may focus on its pinning as show on arrangement it is different from from TO-220 package. I have checked it for many time and If you have time , you can research pinning of TO-92 and TO-220 to compare pinning arrangement.
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On photo , It is a 7815CT which is a good condition.
Input and ground has high input resistance range Mega Ohm.
Output and ground has high input resistance range Kilo Ohm.
On photo , It is a LM317T which is a good condition.
Adjust and output has high input resistance range Kilo Ohm.
Adjust and input has high input resistance range Mega Ohm.
Adjust and output has resistance range Kilo Ohm.
It is divided into 2 method.
1) On board testing .........find part number on ICs for example 78L05 voltage output must be 5VDC , 78L12 output voltage must be 12VDC , then you can use VDC test function on multimeter to check that output voltage if it has output as rated specs means those ICs is still good. In case of input of ICs is normally present , but no output voltage , you have to switch off circuit and remove the ICs from PCB to check it as off-board testing.
2. Off board testing ......after removing the ICs from PCB then set multimeter to resistance test function., connect test leads then measure to read resistance value.
2.1 Measure Input and Ground then switch the test leads as photo and do testing again.
Input and Ground terminal testing , the first measurement.
Good ICs has low resistance value 1 time.
Good ICs has low resistance value 1 time.
2.2 Measure Output and Ground then switch the test leads as photo and do testing again.
Check measurement results of Input and Ground terminal testing with these criteria.
Good ICs ....the first testing and the second testing ( switch test leads )
the measured resistance value get result as
- High resistance value 1 time.
- Low resistance value 1 time.
Bad ICs (short circuit)....get very low resistance ( almost be 0 ohm ) for the first and the second testing.
Bad ICs ( leak )....get very high resistance for both testing ( almost the same value and high resistance value ).
Check measurement results of Output and Ground
with these criteria.
Good ICs ....the first testing and the second testing ( switch test leads ) resistance value get result as
- High resistance 1 time
- Low resistance 1 time.
Bad ICs (short circuit)....get very low resistance ( almost be 0 ohm ) for the first and the second testing.
Bad ICs ( leak )....get very high resistance for both testing ( almost the same value and very high resistance value ).
Read more topics of testing , from here .
