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04-02-2014, 04:58 AM   #1
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Free SMC PENTAX-F 100-300mm 4.5-5.6 struggles !

I have a 100-300mm f4.5-5.6 SMC Pentax-F series given to me with a 1996 Pentax MZ-5 and it does not 'auto-focus' so I use it on 'manual' focus but the other trouble is that sometimes it 'zooms' OK and then suddenly stops at 300mm -- then if I turn zoom ring back and forth a few times something will 'click' and it zooms again !! Is it worth sending off -- my wife doesn't want me to spend any more money on 'Old gear' !! Or can I take it apart myself

04-02-2014, 05:28 AM   #2
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My 55-300 did something similar, after it was damaged. I sent it to CRIS for service, which was about half the cost of a replacement used one. They returned it better than ever, they calibrated the autofocus so now it's really good.

Right now you have a worthless lens. Repair it and you can use or sell it.
Being an old lens, though, the parts may not be as readily available. Do you have a repair service you can ask - and will they provide an estimate if you send it?
04-02-2014, 05:53 AM   #3
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if you turn the focus ring, does the little screw drive coupler turn in the mount? it'll look like a little flathead screw recessed a bit into the mount.

also, make sure all the contacts are clean, a q-tip and rubbing alcohol works wonders (moist, not dripping wet)

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