Pentax DA 70mm Limited - Possible oily residue inside lens?

Started 4 months ago | Questions
OP Wahid Khan 1961 Forum Member • Posts: 59
Re: Pentax DA 70mm Limited - Possible oily residue inside lens?

Phil A Martin wrote:

I've said this before but I'll say it again, it would be either a very brave or foolish person to attempt to do this with little experience, especially on a valuable lens. Better off leaving it to the professionals with years of experience under their belts and with all the tools and spare parts on hand. And if you can't afford it, sell it as spares or repairs to someone who can afford to repair it and at least recoup some of the money you spent on the lens.

Hi Phil

I do appreciate your concern and advice. I won't attempt this unless I have a high degree of confidence in completing this task satisfactorily.

I have repaired a Pentacon 50mm f1.8 and two Samsung NX 20-50mm lenses. The first was relatively simple whilst the NX lens were much more challenging. Small, compact and with about 6 small, fragile ribbon cables to deal with. They were worth the risk as they were relatively cheap.

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lowerCamelCase Regular Member • Posts: 347
Re: Pentax DA 70mm Limited - Possible oily residue inside lens?

Wahid Khan 1961 wrote:

lowerCamelCase wrote:

Wahid Khan 1961 wrote:

That's a real shame, I feel for you.

These 'premium' lenses are not cheap and if such a simple issue can render them useless is very worrying, especially if a simple or cheap(ish) fix is not offered or available.

I am pretty confident that in my country the repair service would fix this. On the other hand, a few work hours (at least what the customer pays, not necessarily the earnings) easily buys a new da70 hd in my country too so I would personally rather get a new one where chances are less it will reoccurre.

Always sad to have a paperweight lens!

Is your lens really 'unusable'? If so, sounds like you have a much more severe case than my lens. Please see image I've uploaded to another comment on this thread.

I do not have this issue with the da70.

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jf_tea Senior Member • Posts: 1,466
have your tried lens cleaning fluid ?

If the oily residue is on the outside surface of the back element, have you tried cleaning it with lens cleaning fluid ?

It should work. If not on the first try, maybe after 2-3 times.

I've cleaned that surface of several lenses with good results and not much difficulty -- except the deeply recessed back element in the old S-M-C Takumar 135/3.5 -- but I succeeded, with the help of a coton swab

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-JF

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OP Wahid Khan 1961 Forum Member • Posts: 59
Re: Pentax DA 70mm Limited - Possible oily residue inside lens?
3

Success!

A BIG thank you to all who responded with suggestions, especially 'resistingLBA' for the excellent illustrated tutorial. Not sure where you got your info from, but if you worked it out yourself - I take my hat off in admiration.

I also appreciated the responses that I didn't follow - they were all valuable pieces of information to help me make my final decision.

I was going to post a picture of the cleaned lens, but I really can't do it justice. Suffice to say that the oil residue is gone and all looks great.

Step 4 of the above tutorial was the most difficult as the back lens assembly was very tightly screwed on. I couldn't do it by hand. I ended up using a pair of vice-grips. I padded the jaws to protect the metal and made sure that the grip was not too tight and it came loose very easily. This was my only 'heart flutter' moment.

Would I recommend this procedure to others? With the usual disclaimers - yes! It was one of the easiest lens repair/clean I've ever done. As always, knowledge and preparation is key. Knowing how to open the assembly was key.

Recommendation (stating the bleeding obvious)

1 - Read the tutorial/instructions thoroughly.

2 - Make sure you have the appropriate tools. In this case a simple, good quality screwdriver.

3 - Take your time and place the items you remove in a clear sequential manner so you can easily reverse the process.

Thanks again to every one.

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