This rear projection set is about two years old. Picture suddenly shifted up so that only bottom two/thirds show with upper one/third missing. Bottom third of screen is black. The part I can see has good color and convergence only at center of screen, the rest is progressively worse as you approach the edges. I have repair manual with schematics. The three gun assembly is not loose nor shifted. Mirror is OK also, therefore it is an electronic problem. Any help is appreciated.
Thanks,