A joyless jaunt: 135mm f/2.8 AI Repair/Service

The 135mm f/2.8 AI was produced from the 1977 - 1981 and lived in the shadow of its faster f/2 sibling and also had competition from the 105mm variants. Its a compact rugged lens but its not a lens I'd seek out myself except to rip it apart for curiousity

I didn't enjoy opening this lens. There are a few little surprises, too many small grub screws, and things not where you'd expect but heres some notes.

Helicoids

• Remove the front retaining collar and lens hood
  
  Locate the hole on the lens hood that hides the delicate grub screw. On the few copies of the lens I've serviced it's around the 4.5ft marking, It will be difficult to see into the hole so ensure you don't strip the screw head - once the grub screw is loosened, use a rubber tool to twist off the front ring and then slide off the lens hood.
  
  
  
  
  
  When you've removed the front retaining ring - the same that has the grub screw hidden by the lens hood - put a mark on the top of the ring aligned to the grub hole so you can quickly locate it again instead of playing hide and hide and hide and seek in the future.
  
  
• Remove the objective
  
  This is a little different to the shorter (wide-normal) lenses as the objective is secured by 3x screws inside the barrel. Remove the rear mount and then the aperture ring that is secured by 2x screws.
  
  
  
  See the securing screws with laquer seal
  
  
  
  
  
  
• Take note of how the helicoid key sits and where the aperture activtation lever goes for reassembly later.
  
  
  
  
  
  
• Get to the helicoid key
  
  Put marks onto the barrel where infinity is Remove the chrome grab ring and also the distance scale - the distance slotted scale screws are tiny.
  
  
  
  
  
  
• Remove the focus ring and the front
  
  Notice the marks I've made on the rear and central helicoid as the are aligned to infinity. The infinity and MFD stops are under the focus ring.
  
  
  
  
  If you find the helicoids are difficult to turn, you can add lighter fluid to help free up; below I've applied lighter fluid to a kitchen tissue and wiped off some of the old grease. This step will make it easier to turn, and later to seperate. Doing it at this stage with the helicoid key in place means I can do an intial wipe without worrying about inadvertently seperating the helicoids.
  
  
  
  
  ^{front also contains the (brass) infinity stop}
  
  
• Separate the helicoids
  
  Renove the helicoid key. You can see that from infinity to fully collapsed the central and outer helicoid is very short - literally less than 1cm of rotation.
  
  Seperate the outer and central helicoids and mark then they aligne to other (infinity) reference marks
  
  
  
  Do the same for the central and inner helicoid - you can notice the inner helicoids look relatively clean and you're right as I cleaned some off grease in previous step in preparation to seperate.
  
  
  
  
• Clean the helicoids and the helicoid key with lighter fliuid and IPA
  
  A light NLGI #00 grease is good here but pay attention to the helicoid key when reassembling - because it is a single (heavy) key you need to use a heavier grease on the brass helicoid and its slots otherwise the turning action will bind. When inserting the key I tend to extend the helicoids so the key is secured when the lens is near MFD to ensure the key is not angled.
  
  
• Reassembly gotcha
  
  When re-inserting the objective, ensure that the aperture activation lever is set up like this.
  
  
  
  Once the objective is inserted, temporarily attach the front retaining ring so the objective does not fall out of the barrel and also so you can safely set the lens face down
  
  
• Infinity Focus adjustment
  
  This can be achieved with the lens fully assembled. You will need to loosen the 3x grub screws on the distance scale sleave and slide it down to the chrome grab ring. This will expose the screws of the focus ring - slide the hood forward, remove the 3x focus ring screws and slide forward to reveal the adjustable focus stop, for both infinity and MFD - loosen the screws and calibrate but take care not to over-loosen otherwise the rear side of the stop will fall and you will need to strip down the lens to retreive.
  
  
  
  

Optics

The lens shared the same 5 elements / 4 group optical from the New-Nikkor K to the AI-S.



The elements are mostly from the front with the single rear element housed in a unit that can be spun off but be sure to add IPA to the locking seal hole - even after this I needed some extra torque to unseat.



To get to the majority of the elements you will need to remove the front retaining ring and then carefully remove the front element retaining ring to get inside to more retaining rings.

Apply IPA and wait.

Conclusions

This isn't a fun lens to service as its not what you'd expect if you've done mostly normals (50mms etc). Even compared to another short/medium telephoto the 105mm f/2.5 AI-S won't give you much of a clue. Further to that, its one of the AI lenses with a single heavy helicoid key that can get prone to binding if you dont seat it/grease it right and there are too many small grub screws to handle.

Overal whilst the lens is a good budget option and solidly built as you'd expect for the vintage, personally, its not one that brings much satisfaction upon service completion.