Page 112 - Testing Electronic Components

You can’t test a voltage regulator IC the same way you test on other
components. You have to test the voltage regulator with power “ON”.
That’s right, you have to switch “ON” the equipment in order to
accurately test voltage regulator. Identify the voltage regulator IC in
circuit board first and normally it is label as IC. Look at the part number
and if it is 7808 then you automatic know that the input must more than 8
Volts and the output should be 8 Volts.

Place your digital meter black probe to the equipment ground and the red
probe to pin 3 of the voltage regulator IC. Power “On” the equipment and
see the result. If you get 8 Volts then the IC is working fine. If you get 0
volts or 3 to 5 Volts then you have to measure the input voltage. Make
sure it has more than 10 Volts input voltage. If the input voltage is lesser
than 10 Volts (say 6 Volts), then suspect a fault in the power supply line
or a leaky voltage regulator.

A leaky voltage regulator can pull down the input voltage. Sometimes
bad components in the output line can also pull down the output voltage
of regulator. The best is to direct replace with a new voltage regulator and
retest it. A new voltage regulator IC is very cheap and I encourage you to
keep some spare for yourself for future use in electronic troubleshooting.

You may also desolder (remove) the output pin (pin 3) so that it will not
touch the line but pin 1 and 2 is still connected. Power “ON” the
equipment and check the pin 3 voltage. If there is a good input but the pin
3 output still low (say 3 Volts), most probably the voltage regulator has
turned bad and need to be replaced.

Testing voltage regulator is not difficult and if you have no confident in
testing the IC with power “ON”, I suggest you get someone who have
experienced in the voltage testing to help you out. You may even e-mail

me for the support.

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