AliTonto ) writes:
This LM7812 is in a TV power supply without any raster or sound.
When I power on and test the voltage input at pin 1 I measure no
voltage there but on checking pin 2 (output) I get 12.12volts.
My question is: how can that be? where is the voltage coming from when
the input is not there?
Thanks to anyone who might be able to eplain this one.
AliT

Assuming this is a to-220 package, it's input, ground, and output.
I would never refer to the output as "pin 2". Given that, I'd make
sure you had the pinout right, before looking for some obscure matter.

Michael