Regulator Issue

[kurtlives]

Got a 12V DC 300mA power supply...

When I plug it into a 2.1mm DC jack I get a reading of 17V DC...

So I use a regulator (with heat sink but no filter caps at all). On the input pin I read -3.5V and the output pin reads -2.5V.

The regulator is a L7812CV... I have tried flipping it around so the out is the in but the result is the same... Could I have damaged it by apply the input voltage to the output pin?

What have I done??

[kurtlives]

Mods please delete this topic...