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help to disassemble TOPCON RE AUTO 35/2.8
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PostPosted: Thu Oct 29, 2009 6:16 pm    Post subject: help to disassemble TOPCON RE AUTO 35/2.8 Reply with quote

All,

I am about to disassemble a Topon RE Auto 35/2.8 - can't turn the focus ring. I did some search on the web and would not find helpful info in this regard.

Anyway, I will be taking lots of pictures and notes as I go. However, in case that you have some info, it would be appreciate that you can point me to it. And, yes, please wish me luck in putting it back together!!



Cheers


PostPosted: Thu Oct 29, 2009 9:30 pm    Post subject: Reply with quote

Best of luck - it's a very fine lens


patrickh


PostPosted: Thu Dec 24, 2009 3:10 am    Post subject: Reply with quote

You may be at a slight disadvantage if you can't focus the lens, and it's at infinity, since some possibly important setscrews may be hidden.

If you can focus all the way to the closest setting, loosen or remove the back set of set screw(s) from the front collar. Remove it by unscrewing CCW.

You now should see the overall optical block held in by an outer slotted ring. Remove the ring with a proper spanner. You should now be able to extract the entire optical block. Note, and do not lose, the spacer between it and the focusing mount.

Remove the lens mount (four screws). From here the onion is simple to peel. The focusing collar is held on by setscrews under the rubber grips. Remove them very carefully, they are getting old and brittle.

Of course, as ever, if you split the helical, note exactly where it came apart. Also take some measurements of how long the lens is at some particular focus setting.

Normally the grease on Topcor lenses doesn't turn to glue, but this may be a special case. They are more prone to oil evaporating from the grease and getting in the auto-diaphragm.

The one well-known exception to the grease-glue problem is the 50mm GN Topcors, which are frequently found cemented solid. This is the only late lens with any brass in the focusing mount, and the grease reacted with it producing the classic green glue.

When re-assembling, note that the optical block has a notch that matches a peg on the back of the focusing mount. Easier to put it in first, and then put the lens mount back in.


PostPosted: Thu Dec 24, 2009 4:13 am    Post subject: Reply with quote

@John Shriver: thank you for your notes, appreciate it very much. It will be helpful, if/when I can get the screw off the lens mount(http://forum.mflenses.com/how-to-remove-stripped-screw-off-lens-mount-t23449.html).

After playing with the lens for a while, I found the following symptoms:
- at f2.8, focus barrel can be turned from MFD(0.23ft) to infinity
- at f22, focus barrel can be turned from MFD to about 0.25ft
- at infinity, aperture ring can only be turned from f2.8 to about f5.6
- The aperture ring does not set the aperture on the lens, ie. f2.8 to f22 yields the same lens opening
- pin,which I assume allow for stop-down metering works only some of the time
- the focus barrel would cease at some combination of aperture and pin moment. To un-do it, I have to slide the pin to one side a couple of times and rotate the focus barrel and/or the aperture ring back and forth a couple of times

Cheers,


PostPosted: Fri Mar 19, 2010 11:56 pm    Post subject: Reply with quote

Sounds to me like the stop down lever may not be seated properly in the diaphragm module. You could remove the lens mount, and then unscrew the rear group from the diaphragm module, and then you will have a good look at the focusing mount.

But the diaphragm module is held in by a ring the front that you really need to remove the filter ring to get at.


PostPosted: Sat Mar 20, 2010 1:42 am    Post subject: Reply with quote

John Shriver wrote:
You may be at a slight disadvantage if you can't focus the lens, and it's at infinity, since some possibly important setscrews may be hidden.

I have a Chinon 1.7/55 with exactly that problem. I can find no way to get at the helicoil.


PostPosted: Thu Apr 01, 2010 1:08 am    Post subject: Reply with quote

John Shriver wrote:
Sounds to me like the stop down lever may not be seated properly in the diaphragm module. You could remove the lens mount, and then unscrew the rear group from the diaphragm module, and then you will have a good look at the focusing mount.

But the diaphragm module is held in by a ring the front that you really need to remove the filter ring to get at.


@john, thanks for your followup comments. unfortunately, ran into a different issue where I managed to strip the head of the mounting screws. I now have no way(almost none) to remove the mount to continue the work. Crying or Very sad


PostPosted: Mon Apr 12, 2010 1:18 am    Post subject: Reply with quote

You needed a cross-point (not Philips head) screwdriver, and possibly some strong solvent (say MEK plastic weld glue) to get those screws out without damaging them. One of the key skill in camera and lens repair is getting screws out without damaging them at all. Really good screwdrivers are very important tools.

Now about your only hope is a 1.5mm left-handed drill to try and get the screws out.


PostPosted: Tue Apr 13, 2010 2:06 am    Post subject: Reply with quote

John Shriver wrote:
You needed a cross-point (not Philips head) screwdriver, and possibly some strong solvent (say MEK plastic weld glue) to get those screws out without damaging them. One of the key skill in camera and lens repair is getting screws out without damaging them at all. Really good screwdrivers are very important tools.

Now about your only hope is a 1.5mm left-handed drill to try and get the screws out.


@john: is this the MEK plastic weld glue that you are referring to http://cgi.ebay.co.uk/PLASTIC-WELD-MODEL-KIT-GLUE-MEK-PLASTRUCT-HIPS-/360148907324 ? would the solvent be a problem if I somehow get them on to the lens? The screw on the lens mount is not cross-point, so I do not understand why i want to use a cross-point screwdriver? I may be missing something here, please advice when you have a chance.

Cheers


PostPosted: Sat Jun 26, 2010 8:40 pm    Post subject: Reply with quote

Yeah. that's the sort of MEK I use. Often acetone is strong enough for the screw glue.

Early Topcor lenses used slot-head screws, later ones used cross-point. Yours must be early.