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08-01-2009, 09:02 PM   #1
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FA zooms, Worth Repair? Recommendations?

Appreciate advice from the wealth of knowledge here.

Today I was able to pick up the below two lenses fairly cheap ($75 for the pair).

SMC Pentax-FA 1:4:5.6 28-105mm
SMC Pentax-FA 1:4.5-5.6 100-300mm

Both have the "power zoom" function which appears to work on my k20d. It's actually pretty neat to zoom, and focus with a slight turn of the knob. I like it. Problem is, the lenses are not perfect.

100-300mm works well, but has is hazy on the inside of the lens. I haven't experimented to see the effect on pictures yet. I'm hoping this is a cleaning job I can do myself? Or should I farm it out. Would appreciate insight on how hard these lenses are to open and clean.....or if it's even worth the effort?

28-105mm, the zoom is sticky and stiff on the long end. I can force the zoom manually all the way to 105, but it's a push. Using power zoom, the camera only has the juice to push it out to 65mm. I'm assuming this is another clean and lube job. Again...possible to do myself? Farm out? Or don't bother?

I've read recommendations of Eric for lens repair work. I'm sure there are others. I don't believe it's going to be too technical a repair....more a clean and lube job.

Appreciate the insight.

WiseOx

08-01-2009, 09:19 PM   #2
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If you are willing to send it to Calgary, Vintage Visuals did a sterling job on my old M 400/5.6 with slow aperture blades and a tripod mount that would no longer hold position. Less than $100 including shipping and tax. They are on the web.
08-01-2009, 10:06 PM   #3
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I took apart my FA 28-105mm f4-5.6 Power Zoom lens a month ago. It wasn't that hard, but I've had some experience with less complicated lenses. There are a lot of tiny parts to keep track of. At some stages, it is not clear what part comes off next, but you can more or less unscrew every screw you see and get it apart. Or fiddle with it and figure it out. Photos will help, and keeping track of which screws go where will help too.

For this lens, the optical elements come out as one assembly. You'll see the rollers and grooves that guide lens barrels for zooming. I have some grease designed for lenses. Use any lube sparingly, because it can vaporize and end up on the glass.

The FA 100-300 has 12 elements, so your success will depend on where the haze is. I have the F version which I think is the same thing. The front has spanner slots and a thin plastic beveled ring. I suspect the spanner slots can be used to unscrew the front lens group. The plastic ring can probably be pried off. There are internal spanner slots that might allow you to get to the second group (the one that zooms). The rear group has spanner slots as well. You can probably leave the mount and all its electrical contacts attached and unscrew the three tiny screws holding the black plastic light shield on. These go into the side of the bayonet. Removing the light shield will give you more working room. That leaves one group inside somewhere; hopefully your haze isn't there.

Clearly a lens spanner would be a useful tool for this repair. It's possible to improvise sometghing that works, or buy a tool on eBay. The main thing is, make sure the sharp pointy parts stay in the slots, not go bouncing across anything SMC.

My philosophy has always been that paying for a repair is not worth it, but a lot depends on the lens value, what you paid and your abilities/risk tolerance.
08-01-2009, 10:10 PM   #4
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The FA28-105 (PZ) is alright optically but aperture is small. The FA100-300 is optically poor and not really worth the trouble at any price. Move on if you ask me.

08-02-2009, 02:57 PM   #5
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Indeed, te 28-105 has a good reputation, but the 100-300 powerzoom has a passable reputation at best. The 100-300 f4,7-f5,8 is supposed to be better, but even that one is not worth more than 100$ IMHO.
08-02-2009, 03:50 PM   #6
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QuoteOriginally posted by Just1MoreDave Quote
<snip>

My philosophy has always been that paying for a repair is not worth it, but a lot depends on the lens value, what you paid and your abilities/risk tolerance.
It depends entirely on the relative value of the repaired lens to the cost of repair. My recent repair of the M 400/5.6 to put it back into good working order was about 1/5 the cost of replacing it - so I fixed it. The infamous FA 28-80, on the other hand, is worth precisely nothing in the way of repairs beyond the packing tape I used to hold the loose bits from the power zoom controls in place.
08-02-2009, 08:14 PM   #7
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Original Poster
All I can say, is I love this forum. Greatly appreicate everyone taking the time to pass on their thoughts/recommendations.

Just1MoreDave, an extra thanks for taking the time to walk thru a high level tear down. I may just brave it. the 28-105mm lens seems fine, other than being stiff as hell from 65mm and beyond.

For now, I'm going to try using the lenses for a bit as is. As expected...they are not likely worth much more effort than what I can throw at them myself. I played around the 100-300mm and wasn't very impressed. Pretty soft at 300...but what I don't know is if that's just the lens....or the haze on the glass.....likely a bit of both.

I'll chalk it up to a not too expensive lesson learned in used lens buying.....and an opportunity to tear something apart for fun.

Thanks again all.
01-31-2013, 12:35 PM   #8
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I'm about to do the same thing. Anyone have pictures or additional advice?

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