Exposure unit light ource question...

[The Bubble Process]

I have been using the same set up of -2- 500w halogen lamps suspended above my screen to expose for quite a while. One of the halogen units recently bit the dust and I bought a new one from HD like I've done before. I noticed the new unit is emitting light differently then the other one I have and the light seems to be more intense in certain areas (looks like 3 bright lines). I tried exposing a few screens and I am getting pretty inconsistent burns with areas sticking in the screen and underexposed on the top and bottom.

I have returned the lamp 3 times now and it seems to be the same for all. Has anyone ever experienced this? Is there a way to adjust the reflective flashing inside the light to disperse the light better?

Thanks.

[The Bubble Process]

whoops...typo in the title.