Something
might be loading it down, too. I'd check for that before assuming
it's bad.
I'm not sure I know how to do that. I was just going to pull the
converter and power it up by itself to see if I get -12v out of it.
That's basically how you do it. Remove the converter, power it up and see
if oyu get the right output. If you do, then it's worth trying a sensible
load on it (A 1k resistor?) to make sure the output doesn't drop
spectacularly.
If the convertor works like that, but doesn't work when fitted to the
PCB, then something is overloading it.
-tony