This is the second post in a series of four related to cleaning my used Yashica Mat 124. The first post in the series describes the task in more detail and includes links to all of the other posts.
My second task once I overcame the first hurdle (cleaning the taking lens) was to clean the mirror box, including the viewing lens and the viewing screen. I don’t have any pictures from this procedure, but a great resource for viewing what is involved can be found at David Richert’s Yashica 124 rebuild page. His page has great coverage of removing the viewfinder, replacing the light seal, cleaning the mirror and viewing screens, etc. So I’ll just add my experiences here, but refer to David’s page for pictures and a great description.
Removing the viewfinder is very, very easy. There’s two silver flat-head screws each side of the waist level viewfinder which are easy to access and remove. Just be gentle with them, since they are pretty small screws! After seeing these screws, I will never pick up the camera by the viewfinder again (not that I was doing that a lot in the first place!).
Once I got the viewfinder off, it was pretty clear that I wasn’t the first person to muck around in there. Someone had clearly replaced the light seal against the meter (kind of a small light seal, but it did it looked like a good replacement) and the mirror had clearly been cleaned very clumsily resulting in a ton of little scratches in it. The ground glass and Fresnel lens were in very good condition though, and other than many bits of dirt, everything looked good.
So, the first thing I did was remove the mirror to clean it. The mirror has a clip on the back that I pulled down to slide the trapezoidal mirror out. Sadly, it wasn’t quite as easy as it sounds, since the mirror is small, space is tight, and I had a lot of trouble keeping the clip down. But I got it out by wiggling it back and forth a bit and gently pulling until it came out.
Removing the mirror revealed the focus wheel shaft — that was covered in thickened, old grease (a common problem on Yashica Mats). I tried to clean some of it off, but gave up after it started eating my q-tips! (not eating like acid — eating like a tar pit) The focus wheel is a little stiff, but well damped and controllable, so I won’t mess with that gooey mess until I need to!
While I had the mirror out, I used a lens blower (rocket blower?) to blow the dust out of the chamber, inspected the meter electronics (all looked good), and cleaned the inside of the viewing lens. Overall, very easy and painless.
Next, I turned my attention to the ground glass and Fresnel lens. The ground glass is the part on the top of the viewfinder (closest to your eye). The top of the ground glass is normal, smooth glass, while the bottom is frosted with the red painted grid. The plastic Fresnel lens is under the ground glass with the ridged side facing up (toward the ground glass). Since my camera had some dirt between the two, I decided it would be easiest to just remove them both and clean them that way.
From various articles and forums on the internet, I knew that each of these items (the mirror, ground glass, and Fresnel) are very fragile. The mirror has the silver part exposed and is very easy to scratch when cleaning. The ground glass’s red guide lines are quite fragile and easy to scratch or remove when cleaning. And the Fresnel is just plastic, so it is super easy to mess up the ridges that make it work. So, my plan was to remove everything, then carefully wash them at the sink.
The key part to removing the Fresnel and ground glass were the clips, shown in this great shot from David Richert. At first, I got pretty frustrated because I was trying to push the clips down and slid them out — toward the center of the glass. Once I referred back to David’s page, I realized that I needed to push them down and slide sideways — that worked a lot better!
With the mirror, ground glass, and Fresnel out, I took them to the sink and carefully cleaned them with hand soap, windex at times, and paper towels. The first step was to rinse off as much grunge as I could, then swish them in soapy water to get more off. Finally, I used the tip of my finger to lightly scrub the really dirty areas. After that, I carefully dried them on paper towels, using windex to get stubborn parts streak-free, and that was it. It took a while (a half-hour for the removal and cleaning) but I did not damage them at all!
So, then, I put everything back together. The mirror, in particular, is a pain because of the way the clips are organized. All I can say is, don’t force it! The clips toward the front of the camera often get in the way and I had to push them down with a separate tool. The viewfinder went together a little better (remember, the ground glass on top, lines down, while the Fresnel is on the bottom with ridges up!). On one side my hands got a bit awkward and I ended up scratching the Fresnel a little bit with a screwdriver — I was using two screwdrivers — one to push down, one to slide the clip in. You can see the scratch if you look closely at the image that starts this page.
Once that was done, I put it all back together, and while I didn’t notice a big difference in viewfinder brightness, I am very happy with it. The cleaning was pretty easy, overall, although take your time and be gentle!
Next up: Replacing the light seals.