Yashica D focusing issue

The only TLR repairs I've done so far have been on the cosmetic side, but I have done some focus corrections on SLR lenses and in setting cams on LTM type rangefinders. They were possible because of how each one was designed and engineered to have some built-in adjustability. I'm not sure just how much of that would be available on a Yashica D specifically, but I do know that to maintain the required precision in the entire 'optical path', many times brass or paper shims were used - in singles, at micron thickness precision, or multiples as precision stacks of singles - to modify spacing as-needed. Sometimes calibration requires an optical bench and/or a lens collimator, and those aren't exactly cheap or in plentiful supply on the used market, and are better left for repair shops to tackle for you.

There is one thing that might offer a clue on where to look to diagnose the problem, but not give any instruction on how to affect a fix... a Yashica D assembly chart is available as a PDF file. With a very quick look through, it doesn't show any adjustment points that might affect focusing, but that won't mean they don't exist as part of a named assembly on the chart. You'd just have to know where to look once inside. I'd suspect shims are needed, and not adjusting a screw on TLR's.

It might be possible to get a sense of what piece of the puzzle might be misaligned. If you have - or can make the equivalent of - a small plate of ground glass, you can place it on the film plane and see if the viewing path and the taking path match. If they're both out of focus, it might be a pressure plate issue, or if one or the other is out of focus, it might narrow down what subsystem needs adjustments. 3M 'invisible tape' on a very stiff sheet of clear plastic can be a reasonable one-time substitute for ground glass in a pinch.

I'd be remiss if I didn't offer one caution. There's the distinct possibility that things can be returned in a reversed position, or have something disappear during disassembly that we aren't aware of... and once reassembled it just isn't quite the same as before. That's not to suggest that the fault lies with you, but it might have been due to any earlier owner/tinkerer trying their own fix and failing. There's at least one person on the planet who does know how to fix a Yashica D, and certainly has the calibration tools to bring it back to a working state. Try to contact Mark Hama through his website if you might want his services.

Thanks for the advice!

While researching the problem, other people gave the same advice to others about placing the tape or ground glass and creating what some have called an 'infinity well'. I'm still not sure on how to inspect the lenses this way. Would that mean looking through the front of the lenses to the back film plane with the shutter open? Which I suppose wouldn't work for the viewing lens anyway. If you would, could you please elaborate a little more on how to do that?

I've found a guy in Orlando that does a complete CLA on TLR cameras for $175 which I think is fair. I'm the type that loves to work on cameras myself (perhaps to my own detriment). I've done fine with maintenance on my SLR cameras, but this TLR is a different animal. I was very careful when cleaning and didn't lubricate anything since everything worked fine including the self-timer. If I can't solve this on my own, then I will be sending it to be serviced. The camera is in too nice of condition to let it go. Even the leather case and strap are in near mint condition. I'd rather take the time to understand it myself well enough that I can service it when it needs it, but maybe this one is out of my league. 

Here's a photo of what I'd normally use for 35mm bodies, but 'adapted' to fill the same role on a Yashica A TLR. The plastic piece is frosted on one side, and it's placed closest to the film chamber. Depending on how thick the plastic/glass sheet is, it might require reversing the magnifier lens 180 degrees to adjust the physical distance to the frosted 'plane' that's acting as the film, to get the loupe in-focus to your eye. Normally if you leave the clear cup sitting on the surface, whatever it's sitting on 'should' be in perfect focus, but if it's off by @ 1.58 mm (1/16"), like this is, it gets reversed.

The plastic sheet itself was part of a tabletop business card holder that I took apart to get a suitable sized piece of plastic that was already 'frosted' on one side, then trimmed with a razor saw to get the right width.

You're welcome, lycosa ... and take a peek at some of the simple things too that tend to get overlooked, like a weak spring on the pressure plate, or a guide roller that popped out of it's hole. Sometimes we fixers can overthink a problem, and conclude it must require a complex solution, when it's often quite the opposite.

I did remove the lens completely going by a YouTube video and I did not match the focus. The guy never mentioned that. I have a lens tool and just popped it back in and secured it reasonably tight. That could be the problem... if so I suppose the recommendation above would fix that as well by loosening the lens to a focal point? I figured the focus would match as the lens seated tight...