| Author |
Message |
    
Ben_hutcherson
Tinkerer
Username: Ben_hutcherson
Post Number: 15
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 23, 2006 - 11:00 am: | 
|
I just got this lens the other day, and have noticed a very odd problem with it.
Basically, when the lens is mounted on the camera, it stops down according to the position of the aperture ring regardless of the position of the stopdown lever. The aperture signal lever still operates as it should.
What this means is that with the lens mounted on a manual body like my FTb, it has to be stop-down metered, as the lens will only remain wide open when the aperture ring is set to 2.
On an AE body, like my A-1, T70, or T90, the lens can be set to A and won't stop down until the shutter is pressed, although it won't open back up until the aperture mechanism is reset.
Does anyone have any suggestions as to what I need to be looking for?
By the way, happy Thanksgiving to those of you in the United States.
Thanks,
Ben |
Glenn
Tinkerer
Username: Glenn
Post Number: 111
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 23, 2006 - 03:25 pm: |
|
From what you describe, I would think that the rear mount assembly has been removed, by somebody with little knowledge of FD mechanics. On re-assembly the inner portion of the stop-down lever, has not been replaced in the 'U' section of the inner actuating lever. It is also possible that damaged/broken coil springs could be a contributing factor.
A very useful 'tool' for checking FD lenses is the 'Mk1' Macro Hood. When inserted in the mount, the actuating levers are unlocked, thus you can work the levers by hand whilst viewing the rear of the lens. The 'MK1' has the separate plastic lock for manual operation, on the later type the lock is cast into the hood - thus you cannot work lever by hand.
This tool can easily be made by cutting the base out of a rear lens cap, and also removing the 'stops' on the three mounting lugs. This enables you to fully rotate the modified cap in the mount, thus unlocking the mechanism.
If you are not familiar with stripping the new FD lenses, note the following: Only remove the three + head screws that retain the stainless bayonet ring in the lens barrel, then pull the ring free with the aid of a rear cap. The complete actuating mechanism can then be lifted free. This mechanism is the 1.4 type and contains approx 100 steel balls balls ( the 2.8 type has no ball bearings and is only fitted to the cheaper FD lenses. The type nos comes from the respective 50mm standard lenses that these mechanisms were originally fitted to). Do not remove the three, radially placed, small counter-sunk screws to separate the rear mount mechanism - unless you like chasing the little sods!
With the rear mechanism off, you will easily see the 'U' shaped receptacles for the inner parts of the mechanism levers. Correct replacement requires you to hold the outer levers in the correct position, whilst you locate and twist the assembly into position. Sounds more complicated than it is - you soon get the knack. |
Ben_hutcherson
Tinkerer
Username: Ben_hutcherson
Post Number: 16
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 23, 2006 - 05:19 pm: |
|
Glenn,
Thanks a bunch. I was able to get the levers reseated correctly, and everthing seems to be working correctly.
I appreciate your help.
By the way, a macro hood is one of the items on my "to buy" list. Until then, I have a handful of items that I use for the same purpose now, including a mirror box off of a parts TX and an FD25U extension tube. A macro hood sure would make things a lot easier. I'm also a bit short on rear caps now(I've ordered some, and am waiting on their arrival), so am a bit hesitant to convert one of the ones I already have. |
|
