Rectilux HCDNA Disassembly

November 7, 2018

It’s time to tear a Rectilux HCDNA apart for a mod project. It’s a useful tutorial for regreasing and general servicing.


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Tito Ferradans here for an oddly technical video on how to take things apart: let’s rip open a Rectilux HCDNA. The wisdom for this process was originally imparted on me by Ian Edward Weir – you should definitely check out his content – and you can find a link to his website as well as the written version of this tutorial in the description below.

Why am I taking a HCDNA apart? My fellow Vancouverite Victor Prokopowicz was having some trouble getting the HCDNA close to the front of his Kowa 1.75x. He wanted to mill the back of the HCDNA a bit wider, but wasn’t insane to try to do it with the glass still on. He was also not comfortable taking it apart by himself, so we made a deal I could make some episodes with his gear if I helped him out. Here I am.

Taking your HCDNA apart is also good to fix stuck-focus issues, regreasing, taking off excessive grease and cleaning in between the glass too. This was a much more challenging process than I expected, but everything and everyone made out alright. And you’ll be able to see the video about that Kowa soon, so hit subscribe now and be done with it.

Let’s go.

As an easy warm up step, let’s get all the clamping screws out. This will set up the mood for everything to come, and it’s an easy enough step that no one can mess up.

Now, with gloves and lens wrench, I’ll remove the locking ring for the rear glass. After that, carefully drop it onto your hands and place it in a safe area. Move to the front and remove the locking ring. These steps make me extra nervous because I can’t have the lens wrench slip and hit the glass. After removing the ring, turn the lens so the glass goes safely on your hand. Put it aside too.

Now, remove the three small screws around the focus ring and now it kind of spins freely, so I went to minimum focus and then pulled off the focus ring. Naked helicoid now. Lots of grease.

The next step is to take out the screws that lock the cam sheaves. There’s three of them. Move on to the drag ring that sits at the bottom of the main body. After that is removed, only the sheaves hold the focus mechanism to the main body of the Rectilux.

This is me just being stupid and trying to take out the sheaves from the wrong side. They’re held by pressure and you just need to push them from inside so they pop out. I tried to wedge them out and wasted a ton of time in that process. As soon as they get a little loose, the ring with the RECTILUX engravings comes out.

After that I realized my mistake and just used tweezers to push them out from inside and then pull the rest from outside. Tiny things for big fingers. That releases the helicoid, and you can say you’re done with the first part of the process.

We’re gonna mill out the area with the 75mm male threads.

And this is what we got. A few milimeters wider and good enough for the Kowa. So let’s begin reassembling.

We got the grease John Barlow recommended, Mobil-28, which is an aircraft grease. I used q-tips to spread it good amounts of it as evenly as I could over the helicoid. Also, I’m doing this without gloves and it really sucked. The best way to clean out the grease is lighter fluid and that messes up your skin. Don’t be like me.

After you have a good layer on the helicoid and the base piece, slide the helicoid in place and lock it using the big ring that goes on the base – add some grease to the bottom of this ring too. From my understanding, this ring controls the drag of the lens, if you want focus to be stiffer, tighten here more. If you want it to be more loose, don’t push this too far, but always keep it below the lip of the main body.

Check for grease spill and clean it. We are stuffing this baby with grease and there’s red stuff going everywhere.

Rotate the helicoid so the bottom of the cam curve aligns with the slots in the main body. Now slide in the piece with the Rectilux name (the name should be aligned with the white marking in the main body) and align the holes in it with the guides inside the main body as well. The cam sheaves have to go through all these pieces to lock everything in place. Once you put everything in place, push in the little pins, one at a time.

Make sure everything is flush and then put back the screws inside the cam sheaves. Do not overtighten, go just enough so they don’t protrute from the surface of the helicoid.

Slab some more grease on the outside of the helicoid and then slide over the focus ring. Align with infinity and insert the three tiny screws. Make sure they don’t go too deep, just enough to lock into place. John recommends using threadlock on these little guys and the drag ring inside. I did not do that. I’m traumatized from stripping screws.

Anyway, after you fit the focus ring and lock it, give it a whirl to make sure everything moves accordingly. Go to the minimum focus mark and let’s put back the rear glass.

Of course I got some grease onto the glass, so I had to do some passes of lighter fluid to get it clean. Dust off, and done with this. Move to the front glass and repeat the process. It would be really smart if I just switched gloves, but I ran out of gloves in the middle of the process, so I resorted to cleaning the glass repeatedly to get rid of the grease.

Once the glass is locked in place, do some repeated full focus turns to spread out the grease better. Some of it is gonna come out on the ring with Rectilux written on it, so you might wanna clean that off.

As I said, I got grase everywhere, so I spent a good amount of extra time wiping this entire thing with lighter fluid and making it clean. Our last step is the reverse of our first, putting back in place the clamp screws.

That concludes the process of putting it back together, now with a wider back that can fit bigger lenses. If you’re following these steps, please be super careful with everything, wear gloves, use proper tools, and I highly recommend filming everything so you can easily backtrack what goes where.

Like the video if you enjoy hardcore lensporn and if you have any comments, please leave them below! I urge you to subscribe before you go, as I’m always trying to grow this channel and make sure beginners have a reliable place to look for knowledge. Thank you for watching, and I’ll see you soon. Tito Ferradans out.