testing voltage regulators

[yeepman2]

Is there any way to test 3 termanal positive voltage regulators (mc7815ct),like checking transistors with a diode checker?do they need to be removed from the circuit?

[2muchstuff]

If it is not putting out it's rated voltage under load or not then it is bad. They are not like a transistor where you can put a checker on them.

[gar]

060310-2014 EST USA

yeepman2:

In circuit you could probably test for a shorted regulator with an Ohmmeter.

Otherwise apply power to the 7815. Should be at a minimum about 3 V above the regulated output to get regulator action.

If you have 18 V input, then the output should be close to 15 V.

If you have a short circuit load, then the regulator will go into current limiting and it will get hot.

If the input is 18 V and there is no output voltage and the regulator is cold, then there is an open circuit between input and output.

With 18 V input if the output voltage is not close to the correct value, then check for oscillation.

If the output volage is high, then regulator is probably shorted or the common lead is open.

With the common lead open and no load the output voltage will be near the input voltage. On a 7805 with 12 V input and 1000 Ohm load the output was about 8 V.

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