White spots on screen i have changed the lamp

It's probably you have a busted DMD chip, have your technician replace that, better yet buy a new projector because replacing that chip costs almost a brand new unit.

Hello there and welcome to fixya
Image Problems

• 1 Check the connections of the video cables connecting the the projector to your DVD player, computer, game console or other device. Unplug, then firmly reconnect the cables.
  
• 2 Make sure the projector is set to the right video input.
  
• 3 Remove the cap before use. Some Sanyo caps are semitransparent and allow a blurry image to be projected.
  
• 4 Release the lens shift lock if your lens shift controls are not working.
  
• 5 Change the image focus to try to fix a blurry image. The focus controls one of the rings around the lens array; the other is the zoom.
  
• 6 Increase the contrast or brightness options if the picture is unclear or not bright enough.
  
• 7 Change the projector's ceiling/rear orientation options if your picture is vertically or horizontally reversed.
  
• 8 Replace the projector lamp if it has more than 2,500 hours of use logged.