Open the camera and find the viewfinder moving parts, as you can see in the next photo:



Inside the viewfinder, you will find two lenses that move back and forward driven by a sort of a cam shaft. You should have also a spring that that keeps the lenses tied together (the shaft and the cams have two functions: they just keep the lenses separated at a lenght that varies with the zoom you are using, and they keep the lenses at a different distance from the fixed prysm that you actually look into when aiming).

By switching on the camera and zooming, you should see the lenses (both of them) move back and foward, and get closer one another.

There, you should find what's wrong.

• Maybe you have a broken pin (the pin locks the lens to the cam on the shaft), and that was my problem.
• Or you can have a "hardened" mechanism (maybe dust has gone in) and the clutch that's on the camshaft slips, so the shaft does not move at all.
• Or maybe the pins on the lenses have run past the end and have "fallen out" of the cam, so they rest in a fixed position.

Check if the viewfinder correctly focused (but not zooming) or is it out of focus (but somehow zooming) or none of the above.

If you have a broken pin, you must take apart the viewfinder and reconstruct the cylindrical plastic piece great about 1,5x1 millimeter. In order to do it, I have used a little drill, superglue, and a slice of wire of galvanized iron.
In the next photo, inside the white circle there is the piece that I reconstructed and I have glue in place of the broken one. Lower, close to the bottom of the photo, it's possible to look at the original piece.



If the camshaft doesn't move at all as the lens zooms, probably is a slippery clutch problem. Try to move the camshaft manually, it should move the lenses. Be careful not to go past the end. This is just to see if the mechanism (cam, pins, spring) works. If it works, go on and try to fix it.

First, try to remove dust from the mechanism and see if the clutch works again. This should become very complicated, but it's really better to make the lenses moove smoothly than to glue the clutch, because it will prevent major damages if somehow in the future a lens get really stuck. If not, you can glue it fixed, but you have to be VERY careful to glue it in the correct position, or you will have a premanently unaligned viewfinder (and you can also break the gears because it will run past the end).

To fix the clutch in the right position, switch off the camera (this moves the lenses to the "zero" position), then manually move the camshaft until the lenses are all forward, you'll see that there's a notch that prevents the pins from falling off the cam (and prevents you from turning the shaft more). Then turn it back just a litte (about 1 or 2 millimeters) and fix the clutch by putting a little superglue between the gear that drives the camshaft and the camshaft itself. (really a little, so you can eventually break it and retry).

It should be better to disassemble it and try to make it less slippery but not totally fixed, but it seems to be really too difficult to disassemble.

If the viewfinder is completely jammed, and the lenses cannot move try to rotate the black plastic camshaft and see if it can rotate (only the shaft, not the gear that's attached on its back). Try to slide the lenses away one another (the back lens backwards, the front forward) to see if they move. Sometimes the lenses pins (the ones that touch the camshaft) get stuck to the camshaft, because of dirt or because they "jump" on the cam instead of sliding near it. (this is caused by a shock or by consumption of the plastic pins, that get shorter and so they don't stay in place anymore)

Thanks to: Maneanke.net