Does the transistor tester recognize this type of voltage regulator or is there something wrong with my tt's ?
I am far from qualified to say, but would think it very challenging to automatically detect and test a LM78xx voltage regulator within the scope of everything else this design does, without causing damage to components it already tests for. There are at least 3 challenges that I can think of off the top:
The 78xx series needs a supply voltage 2.5v higher than the regulated voltage, so in the case of the LM7812 pictured, it would have to apply 14.5 volts to the input. Not only does that have to come from the 9v battery, it can't cause damage to the low voltage devices this is designed to test.
The 78xx series come in a TO-220 case but are really more of a 3 terminal IC than a component. I don't know exactly what the transistor count is, but it's a busy little block diagram in the datasheet.
The 78xx series require a couple of external components to function properly. I think those would have to be switched into the circuit during the detection/test phase to properly test the output.
Of course, given all the challenges the designers have already overcome, I would never say "never"! But for the moment, maybe you are better to whip up a discrete test circuit of your own. Don't forget to add a heat sink to that thing if you draw more than 500mA while testing, or the thermal overload protection may shut it down, making it appear to fail the test.
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