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Unresponsive focus ring - Panny 20mm

Discussion in 'Native Lenses' started by wawa, Feb 13, 2013.

  1. wawa

    wawa Mu-43 Rookie

    10
    Sep 16, 2011
    The focus ring on my Panasonic 20mm f1.7 lens doesn't work anymore. No matter what focussing setting, auto focus or manual, it's stuck at ~1m focal length and nothing will change it. The ring itself feels like it's rotating freely -- just smooth plastic against plastic -- as though nothing is catching internally. While on, the camera is scarily sluggish.

    I just moved so I'm afraid it was banged (I can't remember doing so though).

    Has anyone had this happen? Any thoughts on fixing? I'm not afraid to open the lens if I thought I could do something to help. As far as I can tell the actual optical assembly is well contained and the focussing assembly is accessible.

    With other native lenses focussing is just fine, so it isn't the camera itself.
     
  2. speedandstyle

    speedandstyle Mu-43 Hall of Famer

    First off clean the contacts and make sure they are not damaged. If that doesn't fix it then you have problems. If it won't move with either the ring or AF then it is one of two things.

    #1 the focus motor has failed
    #2 the lens assembly is physically stuck

    Does it make any noise? The 20mm is notorious for making lots of noise when focusing. If there is no noise my bet would be #1.

    I do not recommend you try to fix this yourself. Check with professional lens repair services and see what it will cost to fix.
     
  3. wawa

    wawa Mu-43 Rookie

    10
    Sep 16, 2011
    Thanks.
    When the camera boots it's _trying_ to do something. It's not hunting for focus because the focus isn't moving but it's hung up trying.
    The contacts are just fine.
    The focus ring rotates smoothly -- too smoothly.
    If it's the actual motor... that sucks for sure. There's a chance something less critical is off axis.
    I'll look for local Panny approved lens repair service. Sigh.

    Cheer!
     
  4. laptoprob

    laptoprob Mu-43 Regular

    38
    Jan 28, 2010
    Damn! Same thing here. Lens focus got stuck without doing anything. Unresponsive, stuck at infinity I guess. The motor burrs when powering on.
     
  5. laptoprob

    laptoprob Mu-43 Regular

    38
    Jan 28, 2010
    After some searching on the net I found the cause. I have a step-up filter ring 46-52 on the 20mm, to be able to use the same filters on more lenses. That gets screwed in just a little too tight. So I need a little bit of spacer in between...

    sigh!

    cheers, Rob
     
  6. Dc5e

    Dc5e Mu-43 Regular

    31
    Apr 15, 2012
    You do know that all native MFT lenses are focus by wire, right? So if it's rotating smoothly, that's actually a good thing.

    If the front element doesn't move at all when you try using autofocus, then either the motor is damaged, or the lens is not communicating properly. You are able to shoot at different apertures yes?
     
  7. speedandstyle

    speedandstyle Mu-43 Hall of Famer

    I had a screw on hood on my early style Olympus 14-42mm and it caused problems so I removed it. With some of these lenses you have to be careful with screw-on accessories!
     
  8. HarryS

    HarryS Mu-43 Top Veteran

    918
    Jun 23, 2012
    Midwest, USA
    I also say the same thing. Not something for most do-it-yourselfers.

    However, I do recall, but cannot find a recent post here where a 20mm owner did take apart his 20mm and it was something simple.

    This LensRentals.Link was cited as a guide for disassembly.
     
  9. peteyang

    peteyang New to Mu-43

    5
    Sep 2, 2013
    I am having the exact same problem as the OP. Has anyone found a solution to this problem or the original post where the 20mm owner took apart his lens and fixed the problem, as HarryS alluded to?

    Thanks in advance for everybody's help!
     
  10. meyerweb

    meyerweb Mu-43 Hall of Famer

    Sep 5, 2011
    pete, do you have a filter step-up ring or lens hood mounted?
     
  11. HarryS

    HarryS Mu-43 Top Veteran

    918
    Jun 23, 2012
    Midwest, USA
    Looked again. No luck. Maybe he had some debris caught in the focus motor gear.

    By the way, you have to understand how the ribbon cable connectors work if you take things like these apart. Most have latches that easily break if forced the wrong way.
     
  12. peteyang

    peteyang New to Mu-43

    5
    Sep 2, 2013
    Thanks for your inputs. The Panasonic lens is mounted directly onto my GF5 camera and there are no rings or hoods on the lens. I can hear the lens motor turn for a few seconds when I power the camera on, so I'm thinking I may be able to fix the problem by taking the lens apart. Hopefully the problem will be obvious once I open it up.
     
  13. peteyang

    peteyang New to Mu-43

    5
    Sep 2, 2013
    I was able to take apart the lens following the dis-assembly guide on Lensrental fairly easily without any problems.

    I cleaned most of the lens body with a cotton swab and some alcohol since there were some sticky residue on them. The focus motor was a bit hard to turn but I was able to rotate the gear after a little bit of force. It now rotates freely and I can feel all the motor internals moving correctly.

    When I reassembled everything, the auto-focus and manual focus ring still do not work. Does this mean that my focus motor has gone bad? Is there an easy way to verify this? Also, how much does a motor cost and where would I purchase it from, Panasonic directly?

    Thanks!
     
  14. speedandstyle

    speedandstyle Mu-43 Hall of Famer

    I doubt you can get a motor from Panasonic. Best thing at this point would be to have it serviced by a professional as it is more than just dirty.
     
  15. peteyang

    peteyang New to Mu-43

    5
    Sep 2, 2013
    Lens FIXED!

    So I was able to locate the original thread about how someone disassembled his Panasonic 20mm f/1.7 lens and fixed his problem by cleaning the gears after he opened his focusing motor gear box:

    http://www.dpreview.com/forums/thread/3373505

    I followed his tip and cleaned the gears of my focus motor and it still did not fix my unresponsive focus ring problem.

    I was, however, able to fix my lens with the help of a functional lens after I began isolating the problem by swapping out each part that I thought could cause my lens to not focus anymore. I hope this post will help others troubleshoot their problem.

    Here are the steps that I took to troubleshoot:

    1) Disassembled lens and cleaned all moving elements of dirt and grime. Did not fix the problem.

    2) Opened gear box of focusing motor gear train and cleaned off all old, dried up lubricant with a needle tip and re-lubricated with R/C car gear lube. Did not fix the problem.

    3) Swapped the PCB from my lens with the PCB from the working lens. Did not fix the problem.

    4) Swapped the optical manual focus ring sensor with the working lens. Did not fix the problem.

    5) Swapped the optical lens assembly position sensor with the working lens. I rotated the lens assembly so that the barrel was fully extended out of the lens body and ensured that the optical sensor did not have anything in its optical path.

    After I put everything back and turned on the camera, the lens retracted back into the body and started working again to my surprise! I tested it in both AF and MF modes and the lens works perfectly again. I believe that the lens may have "lost" its position and extending the lens assembly fully without the optical position sensor engaged may have allowed it to reset and home itself once it was powered on.

    The other working lens also works perfectly with the optical position sensor from my once-defective lens. So both of the 20mm lenses are now working flawlessly in both AF and MF modes!

    As a side note, I contacted the Panasonic National Parts Center at (800) 833-9626 thinking that I may have a defective focusing motor. It turns out that they do not sell any internal parts to the lens except for the PCB. Its price is $105.06 plus $16.95 shipping. FYI for everyone's future reference.

    Here's the link to the dis-assembly guide once again:

    http://www.lensrentals.com/blog/2012/10/panasonic-pancake-dissections

    Thanks for everyone's help in troubleshooting the problem to my lens and I hope my post will help others fix their lens in the future. :thumbup:
     
    • Like Like x 1
  16. HarryS

    HarryS Mu-43 Top Veteran

    918
    Jun 23, 2012
    Midwest, USA
    Good story. Nice work!