: : I'd be inclined to say off the map to the north. I didn't see it on the map, but the plain in front of it is.

: Well no wonder I couldn't find it!!! Is it on any map?

Map or no map... Angband's gates were 150 leagues from the bridge of Menegroth (Silm, Of the Sindar). Unfortunately the map of Beleriand doesn't have a scale, and I don't know which measurement Tolkien used for his leagues (the definitions I've heard range between 3 and 6 miles). But I believe it is also said somewhere that Dorthonion is 60 leagues wide, so we could estimate Angband's position from that (if the boundaries of Dorthonion can be determined, that is). Perhaps this helps.
-Foradan