If you notice a black background usually multiple and irregular white dots (something like a starry night sky) then your projector has a serious problem on the DMD chip.
The image you see is similar to this …
This problem usually appears in cheap DLP models wearing cheap version of DMD chip, let’s name a few random models ….
optoma HD65,HD20,HD70
BenQ W1000,W1100, W1200,W700
Generally involves small class models (>
Of course the same applies to the corresponding DATA models.
To problem lies in glued mirrors (pixels) of DMD. H this damage comes in unspoken moment and cannot be correlations with hours or projector’s operating environment.
Let’s see in more detail what exactly happens ….
The DMD chip consists of small mirrors which undertake to play the role of pixels and have the ability to move with a deviation of 10 degrees on the vertical axis (and 12 degrees some new models).
If a mirror on the move-10 degrees then ceases to reflect light towards the lens, so as a result you will get black mark on our image to the specified pixel.
On the other hand if by move + 10 degrees then I get white stigma in our monitor at particular pixel, the sample that the mirror reflects all the possible amount of light can. Of course depending on the speed that “snaps” the mirror creates and the corresponding shade of gray (i.e. reflects the proper amount of light).
What happens to the damage that we are that some mirrors stick in position + 10 degrees and thus reflect light even when accept command for non-reflection (-10 degrees).
Unfortunately this damage is irreversible and in fact the only solution is to replace the DMD. The market unfortunately doesn’t move all DMD models for purchase (there are some but not all) and usually order or replacement by delegation deemed unprofitable and sometimes impossible.