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Paul McKinnon
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 24, 2005 - 10:15 am: | 
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This lens - SMC Pentax-FAZoom, 1:3.5-5.6, 28-80mm - is cira early to mid-eighties.
It must have been bumped or dropped by the previous owner as the focusing elements do not focus.
The main problem is that the forward barrel containing the focusing lens elements moves freely in and out of the main lens barrel BY HAND and seems to have lost it's functional connection to the focusing ring on the outer barrel. The focusing ring itself turns freely but does not effectively manipulate the lens elements.
On the plus side, the zoom elements seem seem to function properly and the aperature blades within the barrel stop down to the set aperature.
This lens was a "freebee" but could be put to good use if repaired.
Thus far, I am completely inexperienced in camera or lens repair - but have nothing to lose in attempting to fix this lens.
If anyone has had any previous experience fixing this type of lens your help (the more specific, the better) would be greatly appreciated.
Thanks in advance!
Paul |
Paul McKinnon
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, September 25, 2005 - 10:59 am: |
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Addtional Notes:
1.
I know that this lens is just a shade newer than what has been defined in this forum as "classic" - but posting my repair problem here was suggested by a regular contributor to this site.
Also, I do have some "classic" cameras and lens, some of which require repair, but, I thought I'd start with this newer lens first - just to get my feet wet!
2.
I was erroneous in reporting that the zoom via zoom ring functions properly. It is possible to move it through the full range (28-80mm), but, during rotation, it tends to come up against something internally near the 80mm mark.
I can get it to move right to the 80mm mark by fiddling with the focusing ring and/or it's loose barrel but, obviously, the zoom function does have problems.
Again, any help would be greatly appreciated.
Thanks.
-Paul |
Henry
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, September 25, 2005 - 01:46 pm: |
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Although it is a bit newer than what we usually work on, it does fit the classic Pentax K-mount. So it qualifies...guilt by association. However I have never opened one. If you have some closeup digital pics I'll see if it is similar to anything I'm familiar with.
Many zooms come apart in the middle.
I would start the exploration by looking for obvious setscrews on the focus and zoom rings. Failing to find any I'd try slipping a thin bladed something (not sharp) under the focus ring rubber cover to see if there are setscrews underneath. With setscrews loosened the ring/collar might slide out of the way and reveal the zoom guide pins.
Of course I'm just guessing at this point.
Henry |
Paul
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 28, 2005 - 08:30 am: |
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As suggested, I removed the rubber cover from the focusing ring and found - if you can believe it - TAPE. Yes, the halves in the upper lens barrel where held together with two strips of tape.
Once the tape was removed, the halves separated and revealed a loose plastic piece resembling a piston with the top cut off.
The piston has one outer tracking thread to move the upper element in and out for focusing and one inner set of three tracking threads to move
the piston in and out during rotation of the zoom function.
There are also 3 sets of protruding vertical tracks in the inner piston.
The 'piston' had been jarred out of it's socket - which is why the focusing lens elements moved in out freely, independent of the focusing ring.
It is the inner set of 3 tracking threads combined with the 3 protruding vertical tracks which require attention during reassembly.
To re-insert and lock the piston in it's place in the lower barrel:
- the lower barrel has within it, a protruding tube containing the zoom lens elements.
- remove the 3 set screws and the metal ring found on the top of the protruding tube.
- there are three sets of two pins found on the outside walls of the protruding inner tube,
- align the piston, round edge on top, such that the outside pins on the protruding tube will slide up between the inner tracking thread and the vertical protruding track when you slide the piston down into place.
- the piston should simply lock into place and then spin freely in and out of the lower barrel as you rotate it clockwise. Here, the 3 sets of inner tracking threads should track between the pins for each of the 3 sets of guiding pins.
- also, the vertical protruding tracks of the inner piston should be aligned with the holes for the set screws on top of he protruding tube.
- re-install the metal ring such that it's extended tabs fit itside the vertical tracks and insert and install the 3 set screws.
- next, simply thread the top lens barrel - anti-clockwise - back onto the pistion.
- once "tight", you will have to back it off until you find that the zoom fully extends and retracts without binding throughout the full range of focus.
- retape the upper barrels together at the focusing ring, then check to make sure that the lens will focus properly throughout it's full range.
- install the rubber focusing ring and you're done.
MY MAJOR MISTAKE:
As I mentioned before, I am a complete novice at camera/lens repair - which is why, at one point during the experimental phase of repair, I removed the lens mount from the bottom of the lens.
Of course, all manner of electrical contact springs and other assorted whirlyjigs were set flying in all directions. I lost one of the tiny springs and broke an electrical contact bridge - which essentially has renedered this lens useless.
As of now, I'm searching for parts lens. Wish me luck! |
Henry
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 28, 2005 - 02:50 pm: |
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The lens should still be fully useable on a non-electronic body...even with the broken bits.
The spring you can probably make. The broken electric bridge can maybe be jumped?
Looks like your first go at camera tinkering was fairly successful.
Henry |
Paul
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 28, 2005 - 03:14 pm: |
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I actually fabricated a substitute part for the broken electrical bridge but had to quit (at least temporarily, when I lost the spring.
However, I did find the spring today so will have to make another attempt at repair when I have a bit more free time.
Thanks for your input Henry - much appreciated!
-Paul |
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