Vivitar 19/3.8 FD Disassembly

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Alan WF
Alan WF Senior Member • Posts: 1,611
Vivitar 19/3.8 FD Disassembly
1

A few weeks ago, I was carrying a body and recently acquired Vivitar 19/3.8 FD over one shoulder by the neck strap. The strap slipped, and the body and lens fell about 1 meter onto a hard floor, killing the body and twisting the focus helicoil of the lens so that it was stuck at infinity with the optics misaligned with the mount. Sigh. Now I know not to use neck straps as shoulder straps.

Tonight I finally had time to open it up, but I was not able to fix the helicoil.

However, in case it is of interest to others, here is a description and some photos of the disassembly process. Reassembly is straightforward, except you have to play a little to get the alignment of the mount coupling mechanism right. I'd guess that the disassembly of a Cosina 20/3.8 would be very similar.

If anyone wants my lens for parts, let me know.

Regards,

Alan

1. Unscrew the filter ring to reveal the front element.

2. This will reveal the front element. Remove the three screws that surround it.

3. You can now remove the barrel containing the front optics.

4. This gives access to the aperture at the bottom of the pit for the front barrel. The aperture is held in place by the three screws closest to the axis; I didn't remove it. The three screws furthest from the axis secure the focus ring to the focus helicoil

5. After removing the screws that attach the focus ring to the focus helicoil, you can remove the focus ring. For infinity adjustment, you can probably just loosen these without removing the front lens barrel, twist the focus ring to the correct position, and tighten the screws again.

6. Here is the focus ring, with one of its two mechanical stops.

7. This is what we have. Notice the damage to the helicoil; the silverish ring is twisted with respect to the lower part of the lens, with no gap on the left and a few hundred microns on the right.

8. Turning our attention to the rear of the lens, remove the four screws under the locking ring. You have to twist the locking ring to get access to all four. My lens is FD mount; other mounts will be different.

9. You can now remove the mount coupling mechanism.

10. The back of the lens is now exposed. At 12 o'clock there is the spring and ball-bearing detent for the aperture ring, at 11 and 5 o'clock are the axial guides that prevent the lens barrel rotating in the helicoil. At 8 o'clock is the coupling between the aperture ring and the aperture mechanism. At 1 o'clock there is a pin that is part of the detent for the locking ring.

11. You can now unscrew the rear lens retaining ring, which also acts as the rear baffle. WARNING: once you do this, the rear lenses will be loose.

12. This is the thread for the rear lens retaining ring.

13. You may now remove the aperture ring. (I've replaced the rear lens retaining ring here.) Notice the small ball bearing in the aperture ring detent mechanism at 11 o'clock. Don't lose it!

14. The aperture ring.

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