Help disassembling RMC Tokina 400/5.6

[ektar]

I have started the process of rescuing one of these. I am probably going to have to s*ck it up and buy a 72mm lens tool (unless i can figure some sort of 71mm cylinder I can wrap a rubber glove around), as I need to clean behind the front element. I think the rearmost complex is a glued pair; that assembly unscrews easily. But, I've got two issues:

1- I've got haze on the inside of the second group in from the rear. The retaining ring is deep, and my spanner just does reach in, but at that point, I can't see the tips. So, any suggestion as to how to reach about a 20mm slotted ring down inside about a 1" deep X 22mm tube?

2- Here's where I hope someone has taken one of these apart: The integral hood has lost whatever padding makes it snug when deployed. It's pretty secure when retracted, but won't stay put when pulled into place. I may discover how to get it loose once I get the front element off, but the path is not currently obvious.

Thanks!

[visualopsins]

Okay that was too easy...googled "disassemble RMC Tokina 400/5.6" yielded:

https://www.pentaxforums.com/forums/114-maintenance-repair-articles/238048-notes-disassembling-vivitar-400mm-f5-6-a.html

[ektar]

Thanks for the link. I had seen that one, having worked on one of the Vivitar Komines a couple months ago. I didn't look close enough at the other pics; but even those don't match the lens I have. The SN starts with 87xx, not 28x, 37x, or 6x. The tripod collar is much narrower and the foot is smaller; there are no screws hidden beneath it to remove the mount end. Lastly, the filter size is 72mm; it is not a preset lens. the PentaxForums DB suggests that this one was made by Hoya, but it doesn't resemble the one that is showcased on this forum.

It might help to mention that the copy I have is a Canon FD (not nFD) mount. I would prefer to not take the mount off. I

t does have the two stacked grub screws on the objective end; it may be that that end will unscrew as described; I was hesitant today because one of the sources I found in my search suggested this was also how one adjusts infinity focus, and I was hoping to not screw that up.

[ektar]

Okay. Here's where I am at the moment: The forward grub screw does appear to be the fixing screw for infinity focus adjustment. When that one is loosened, the front complex rotates about a turn and a half and then hits a stop. The rear screw does not appear to do anything while the front complex is assembled; with it loosened individually, nothing moves, and together with the front screw you still hit the stop. At the moment, I'm looking for a roughly 70mm cylinder to wrap and use as a tool for the name ring. Hate to spend the money on a full set of the rubber tools.

[ektar]

Okay: Got the front two elements out and cleaned. Was unable to unscrew the front complex to remove the hood (which is loose when deployed), but did adjust infinity focus. There was some haze on the rear surface of the second group from the back. To access that set, I had to remove the mount (I did not disassemble it).
#1


#2


The top image shows the view down inside the lens. The slotted arm at the left appears to need to engage the nub on the long arm visible in the second image. The other arm appears to engage the other lever. That slotted arm moves very little. I can't seem to get the mount reinstalled such that the aperture control works properly, meaning that the aperture ring adjusts the aperture. AFAIK the aperture worked properly before disassembly.

All help/links appreciated.

[RokkorDoctor]

[ektar]

Thanks, Mark. From what I can tell, your observations as to the operation are correct. I am going to disassemble it again and keep working in the direction you've suggested. What I have run into is difficulty getting the non-confined part of the linkage into correct orientation and operating as expected. A peculiarity of the FD mount is that when the lens is removed from the camera and the mount is in the "ready" mode, the aperture is inoperative. When it is mounted, the "collar" of the lens mount rotates to lock onto the camera side, and the mechanism is ready to operate. The problem with this one as I have been able to get it put together, is that the lever works the diaphragm all the time (which it should not) and the aperture dial has no affect. So, I have something in the wrong place/orientation.

I'll keep at it.

[ektar]

Okay! First, thanks Mark: Your advice matched with what I suspected was the function of the two levers. I was able to get the mount lined up with the levers by pre-loading the bottom lever. What I discovered was that the aperture control arm was somehow not able to move through its throw. As a result, I couldn't turn the mount into proper alignment. I really didn't want to disassemble the lens to get to the workings of the diaphragm control, but with a little experimentation, I discovered that when the open/close lever had jumped loose from spring tension, something got moved out of place, blocking the range of motion of the aperture size control. Moved that back into place, lined up the levers, and Bob's yer uncle. She's got some dust and some off-axis haze, but I look forward to finding out what kind of IQ is there.

[leo_willians]