Some nes zapper games won´t work

[MrHaze]

I´ve recently bought a bunch of zapper games. Most of them work and I can se the white square around the targetobjects when I press the trigger. But in some games I cant hit any targets. I dont even see the white square when I shoot. Any ideas what can cause this??

[Clownzilla]

Have you tried another zapper?

[whoisKeel]

You have it in the 2nd controller port?

[Graham Mitchell]

Are you using an LCD screen or one of them new-fangled high definition TV's? There was a thread awhile ago that explained that conventional light guns won't work with those tv's because they don't have scanlines. Try a 90's TV.