Topcon D1, RE2 chain drive

<p>I purchased a Topcon RE2 with the 58mm 1.4 Topcor for $55. The lens is perfect, and the body is, too, except the shutter speed dial wouldn't turn past 1/8 second to any speed faster, and the aperture coupling to the body wouldn't turn, either. Suspecting the entire coupling system was at fault, I removed the top of the camera and found the the chain had jumped a pulley and was bunched up, causing the jam. <br>

I've re-routed the chain to its proper path, and now the shutter is working perfectly at all speeds, as does the aperture coupling. After inserting a battery, the meter also works, so I have a nicely functioning classic Topcon to complement my stable of big Supers. To boot, the pinion that usually breaks and cripples these bodies is of the brass version instead of the later nylon, so this camera should last as long as the others. <br>

The only problem I have now is that I believe the meter will be inaccurate since the ring gear that couples the lens to the body had come off when I removed the front panel; I need to get the gear to which it couples back to its correct mating position with the ring gear. A search of the net hasn't been helpful.<br>

Has anyone out there dealt with this problem? John Shriver, any suggestions?</p>

<p>No help on the meter, but am wowed by the chain drive idea. Good for you.</p>

<p>Show us some pictures when you can.</p>

<p>Here's a close-up of the gear train.<br>

http://i705.photobucket.com/albums/ww53/Barharbor/th_re2gear.jpg<br />http://i705.photobucket.com/albums/ww53/Barharbor/th_re2gear2.jpg</p>

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<p>Hi!<br>

At least in the Super D/RE-Super, what the chains do is "compute" the exposure value. They are summing up the ASA, shutter speed, and lens relative aperture (stops from open). I think the Super D has two chains, one going from the shutter speed knob to the aperture ring, wrapping around a pulley connected to the other chain. The far end of the other chain rotates the body of the light meter. If the light meter is rotated to a setting that lets little light reach the film, the meter is in a position where it needs to be deflected a lot to center between the two prongs. If the meter is in a position where the film will get a lot of light, the needle doesn't need to deflect much.<br>

One risk of the Super D design is that if you let the chains go slack, the base of the meter will twirl too far too fast, and bend or break the pointer of the meter.<br>

I presume the D1 has basically the same design, but I've never seen a naked D1, and never seen a service manual for one. Obviously the route of the summing chain is different, since the shutter speed/ASA dial is on the front of the camera.<br>

You probably can roughly determine the right setting of the gear along the segment experimentally, presuming that it uses the same rotating meter. You want to be able to rotate the meter from one extreme to the other, with one being ASA 1600, 1/1000, and lens stopped down, and the other being ASA 10, 1 second, and lens wide open.<br>

On the Super D, you do coarse adjustment of the meter by adjusting what tooth in a gear the meter is caught on. Fine adjustment is done by adjusting one roller the chain goes over that's on an eccentric mount. (There are also two selected resistors that control the "slope" of the light meter.)</p>

<p>John, you're right in that there are two chains, performing basically the same way as the Super D, although routed differently due to the position of the ASA dial. I'll mess with it carefully since I don't want to kill the meter. I've never seen a service manual either, but these smaller RE2 and D1 cameras are so great, I'd love to salvage this, especially at the price it came to me. When the lid is off of these cameras, a person really gets a view of some cool engineering!</p><div></div>

<p>Here's a detail of the meter module and the end of the chain that wraps around the axis of the rewind shaft. This pulley appears adjustable since it's slotted/threaded, and locked by set screws in its side. I think this may be for fine adjustment? <br>

The variable resistors are also at this end, I don't want to move them. There are three, so Iwonder if one is gain and the others are slope.</p><div></div>

<p>OK, the Super D manual shows much less chain around that brass gear/pulley when the aperture follower is at rest. What's going to happen in that setting is that as you stop down the lens, you're going to start having two layers of chain on the pulley, and that's not right. They show the first link at 25 degrees to the left of straight up when no lens is mounted (aperture wide open). Even when you have the aperture slider all the way clockwise, there should still only be one layer of chain on that gear/pulley.<br>

The other thing they show is that the floating pulley should be way to the right at B and ASA 1600. Well, one link between it and the end of the track.<br>

You've got the right chain twisted a quarter link, that's why the floating pulley isn't sitting flat. Oh, the left one is also twisted a quarter turn.<br>

So long as the floating pulley doesn't go past the right end of that track, there's no risk of whacking the meter pointer. They note you can tie the chain to a pulley to keep it from whipping the meter.<br>

Note that the right rear pulley has a slot in the top. That's the one you turn to fine-tune the exposure. Position is locked by a horizontal set screw in the body casting.<br>

You may have to experiment a bit to get exactly the right tooth for the aperture gear/pulley to calibrate the meter.<br>

They used chains because they don't stretch like a cable does.</p>

<p>Super-D service manual on this page:<br>

http://www.kyphoto.com/classics/repairmanuals.html</p>

<p>Ah, they used potentiometers instead of selected resistors. Not sure why there are three. See the schematic in Super D manual for an idea, there are two sections of the CdS cell, that are "mixed" with resistors. The "shunt" resistor used to adjust the slope is in parallel with the meter coil. One of those must be that one.<br>

Gain on the Super D is by adjusting the chains. Well, maybe they don't have enough adjustment range on the D1, so they added a gain potentiometer.</p>

 

<p>Double Wow.<br>

Thanks for the pictures. If anything can compete with pictures of the outsides of old mechanical cameras, it's pictures of the INSIDES!</p>

<p>The machine in service of the electronics (in the simple form of the light meter). I love it.</p>

<p>Thanks so much for the link to the service manual. I'm pleased that the RE2 appears to have as robust construction as the Super D, although the D definitely has differing systems, probably due mostly to the use of the Copal shutter in the RE2; of course, its also a smaller body. <br>

I'll post more comments/questions as I proceed.</p>

<p>This shows why Topcons can be said to be "built like tanks". Now, there are stampings in places in the D1 that would be castings in the Super D.<br>

The inside of a Pentax MX is very nice, but everything is so small and delicate compared to the Topcons. The Pentax MX is easier to work on, as well, more modular construction. Pulling the mirror box on the MX is easy (done it), it's a big project on a Super D.<br>

Now, a Leicaflex SL puts both to shame, but it's not clear that Leica sold that camera at a profit...</p>

 

<p>Well, I've stared at this for some time after reading John's descriptive and the Super D repair text, and I'm a bit flumoxed. I took the twists out of the chain, and reset the lens diaphragm coupling gear to about 25 degrees against the coupling lever. See photo.<br />The ASA is at 25 (minimum), shutter is B, aperture is wide open (obviously, since no lens is attached). At these settings, all is well except the chain connecting plate is farther to the left than it should be, and if i move to a higher ASA (50), the chain goes slack. Also, if i manually rotate the coupling lever to the right, the chain doubles over on the the diaphragm coupling gear. <br />It could be that the initial problem the camera had when I got it was that the large left pulley gear had slipped on its axis, but I hesitate to change that, since everything is snugly tightened. <br />Any further thoughts?</p><div></div>

<p>Now I've seen everything... camera bondage. :-)</p>

<p>If the chain around the aperture gear gets to two layers as you move the aperture lever around the mount, you need to start with less chain wound around the gear.<br>

Which chain goes slack? The U-turned one on the left? Or the one on the right?<br>

If it's the one on the right, the anchoring at the meter end on the far right must be set up wrong. That's because the U-turned one should move the "flying pulley" in the middle from the left end of the track in front of the prism to the right end, depending on ASA, shutter speed, and relative aperture. If you can get it to use the entire range, and no more, you have the U-turned chain set up right.<br>

So be sure the U-turned chain has the right range, and them be sure that the right chain stays tight as you move the flying pulley from one end to the other.<br>

Perhaps the spring on the meter isn't loaded up right.<br>

You may have to tie off the right chain, and remove that white plastic assembly from the camera to see what's up.</p>

 

<p>Thanks for checking in. I'm not going to be able to look at it again until the weekend, but I did add some tension to the spring around the rewind axis. I noticed that one of the three set screws is stripped, so that may have been the initial problem, resulting in a de-tensioning of that spring. Surprisingly, the meter has survived this potential catastrophe. <br>

I also noticed that, when the needle moves in response to turning the speeds or aperture, the movement is huge, like 2 stops for what would normally be a .5 stop swing. So some very interesting stuff going on here. I don't intend to give up yet. With a 28 mm AutoTopcor on it, it's a gorgeous RE2.</p>

<p>Oh, and I believe that the white plastic assembly is the meter, FWIW.</p>