Minolta 50mm f1.7 probs

[Peekayoh]

The other day the aperture on my Minolta 50mm f1.7 prime stuck wide open. I suppose that after 25years service (I've had it from new), a problem might be anticipated but I was still horrified (like losing a good friend).
The cost of a professional repair is likely to be pretty high so I got a service manual from Pete Ganzel and got to work. Three hours later, after washing the iris blades in detergent I had the whole thing back together. I think lubricant from the Helicoid got on the blades! Why now?
Going to go out now and take some shots to see if it works.

Peter

[Peekayoh]

Geez, sorry about that ginourmous pic. Should have been like this!

[sparkie1263]

I like a man who isn't afraid of diving on things. I am the same way it can't get anymore broken. When the AF on my Quantary lens started grinding I took it apart and removed the AF drive gear so I could use it in MF only. That looks a little more complicated. I hope everything works out for you. After that operation you can open a lens repair shop.
Good Luck
Frank

PS I can't wait to see what Don has to say.

[Peekayoh]

Thanks, Frank.
I've taken a few test shots and the lens is as good as new; best of all it didn't cost anything (well $25 for the service manual).

I've attached a couple of 100% crops; straight out of the camera no post processing, just downsized, text added and compressed. Nothing memorable about them except look at the sharpness at 1/15th sec hand held. The anti shake system never ceases to amaze me and all thanks to Sony for continuing the Minolta tradition and making my collection of lenses usable. The only annoying thing is how Sony are overpricing the new lenses considering the anti shake system is in-camera.

Peter

[sparkie1263]

Looks great. I wll keep you in mind next time I need my lens repaired.
Frank

[Peekayoh]

It'll get it's feet wet! I'm in the UK.

[sparkie1263]

Then my lens would have have more frequent flier miles then I will ever have.
Frank

[DonSchap]

I admire a man willing to get in there and get his hands dirty! Well, you know what I mean.

Are you sure you weren't fighting a "mold" build-up, because that stuff can get going and takes time to accumulate?
Lubricant, although problematic, sounds like something a bit more ... rare, especially if you had not added any. Guess
I would like to see the cleaning swabs and rags for analysis.

With my two PRIMES having "back-focus" issues, the thought of tearing into the lenses seems a little presumptuous,
as I cannot really "adjust" them without the focusing device they use over at United Camera Repair. It's kind of like
a projector, that passes light through the lens in reverse and they tweak until the graticule is sharp.

How are you, yourself, going to adjust the 50mm f/1.7 back to razor focus?

If there is a detailed procedure, can you paraphrase and post it?

Thanks

[Peekayoh]

No mould Don, clean as a whistle in there (probably some dust now).
There was grease on three of the iris blades. As I said, why now after 25 years, God alone knows and he's not tellin'.

As for front/back focussing issues you'd have to have a collimator (which I don't) to do that. I just made sure not to alter anything that would affect the focus. I know my lens was OK before this problem and I checked the focus after I put it all back together, see attached.

Peter

[DonSchap]

Well, I'm going to let the pros do their jobs. That's what they get paid for. Gotta support that economy.

I turned in four lenses, today, to try and get some of these focus issues resolved.

Minolta AF 28mm f/2.8 (back focus)
Minolta AF 24mm f/2.8 (back focus)
KM AF 24-105mm f/3.5-4.5 "D" (overall softness)
SIGMA AF 10-20mm f/4-5.6 DC EX (overall softness)

They tell me the quotes will be ready by 3:30p, tomorrow (12/4/2008) and I can only hope it is reasonable.
The SIGMA is still under warranty (I bought it last January) and has been shipped back to SIGMA, under
their nickel (I just had to get it over to United Camera Repair, for drop off). In the wintertime, it
will not get the use it does during the other three seasons.

I'll be honest, I do not like that the Primes are this 'horsed up'. They are supposed to be lenses you can
count on, quality-control-wise ... sharp, razor-like AF response, while the zooms, in mass-production, tend
to wander.

I am getting some varied responses from other sites concerning the KM 24-105 performance. Other folks are
claiming theirs is quite sharp ... and admittedly, I did buy it "second-hand" from B&H Video. I would
have hoped they might have inspected it for sharp focus and operation BEFORE they resold it, because now I
am dubious to ever make that mistake again.