I had to change the focusing screen of a Sony alpha 700 because it got damaged when trying to clean it. I did not find any video or info on how to do it on line, so I thought I could do a video and instructions of how to do it in case somebody needs to change it as well.
Here is the video of how I've done it...
Step by step.
I forgot to put some gloves on, but I do suggest doing so, to minimize the risk of damaging the focusing screen.
Step 1. Place the camera on an angle with the viewfinder facing down.( this is important as you don't want other parts of the viewfinder coming out when removing the focusing screen.
Step 2. With a small screw driver, apply light pressure on the focusing screen metal housing.
Step 3. With tweezers, get the old focusing screen out. You may need to tilt the camera a bit to get it out of its place. Be careful not to take any thing else out of there, and try not to get the metal housing out of place, it will be a bit more difficult to place the focusing screen if the metal housing comes all the way out.
Step 4. Pick up the new focusing screen with the tweezers, grab it from the small bit that comes out, not touching anything else with your fingers or the tweezers. Pay attention to the two dots on the screen, they face the internal bit of the viewfinder.
Step 5. Holding the housing with one finger, place the focusing screen in position.
Step 6. With the screw driver, press the metal housing in, paying good attention not to touch the focusing screen. Once in place it will make a click. In the picture you can see how it looks once its in place.
You're done! The same process can be done for cleaning the dust in the focusing screen, using an air blower to get the dust off, never touching the focusing screen with anything, not even a soft cloth.
Enjoy a clean free of marks new focusing screen. Comment if you want me to let you know where to get the new focusing screen.