Manual Focus Lenses Forum

stevemark · Joined: 29 Apr 2011 Posts: 5303 Location: Switzerland

The Sun Auto-Tele 2.8/200mm is a nicely made and pretty heavy (800g) fast 200mm which has pretty much the same size as the conteporary 2.8/200mm lenses from Canon and Minolta. Unlike the Minolta MD 2.8/200mm which focuses down to 1.8m, the Sun has a MFD of only 2.5m - a bit long for tight portraits, but otherwise OK.

My sample came with the usual and well known issues of the lens - fogging and an aperture stuck wide open. Otherwise the lens was in nearly perfect shape, obviously well looked after by the previous and original owner.

Since there's not information about disassembling and cleaning of the Sun Auto-Tele 2.8/200mm I decided to publish some useful information here. Let's start with an image of the lens itself, mounted on a Olympus OM-2 S/P:

Here's the lens from the front end - fogging on several of the front lenses is celarly visible:

Using a lens spanner, the front name ring can be removed easily:

Just beyond the name ring there's a second ring holding the front lens into position. Removing it, again using a lens spanner, is as easy as before:

Now the front lens - a large positive lens which is unusually heavy - can be removed:

Looking into the lens after removal of the front lens:

Exactly as before we now can remove the second negative lens. Be sure to store it properly - it look pretty symmetrical and it's easy to forget which side was in front and which was to the rear ... reassembling it wrongly will result in strong spherical aberrations and very poor corner performance:

There's a spacer between second an third lens - remove it:

After removing the third (positive) lens we can look at the aperture mechanism. You can clearly see the three tiny screws holding it place, but for time being I prefer not to dismantle it yet:

That was pretty easy!

Now lets start from the rear end. There are five bayonet mount screws to be removed. Again pretty easy, no glue involevd (let alone epoxy)!

When you remove the aperture ring be sure not to loose the tiny steel ball:

Now we can remove the rear optical group, again using a lens spanner:

Next: Separation of the two parts of the focusing thread. Extract these two screws and remove the metal guide:

On the other side there's a second guide, a bit more complicated to remove! The crosshead screw is easy, the other one in additions is holding a tiny spring in place. ATTENTION! Do not simply extract this screw as it will destroy the spring! The spring is glued onto the screw, and the glue must be removed / dissoved first with acetone. Once you have removed the glue, CAREFULLY turn the screw and check whether the spring has been freed from the screw. If not, apply more acetone and try again ...

Now we can separate the two halves of the lens barrel.

Be sure to mark the point where they come apart:

Separated!

It's obvious that the aperture mechanism is full of oil which shouldn't be there (separating grease from the helicoids):

The inner part of the helicoid after careful cleaning, first with acetone and then with water/detergent:

After removing the rubber grip (focusing) we can see three small screws:

There's also another, bigger "thing" - no screw head is visible, and on cannot extract it (at least not from this side). Leave it as it is:

Extract the four small screws - ATTENTION: apply acetone first since they are glued in:

You'll get two halves, again:

Turns out that "thing" is the focus limiter - it's screwed in from the inside, but we don't need to remove it:

Now we can separate the outer thread of the focusing mechanism. Clean all threads carefully with acetone an water/detergent!

The aperture mechanism - full of oil - is hidden quite deeply inside the remaining barrel.

While not impossible to dismantle and reassemble, I decided to try to clean it with plenty of acetone, but WITHOUT dismantling. Soaking the entire mechanism in acetone while opening/closing the aperture for quite some time (maybe 50 actuations) did remove most of the oil.

In a second step I repeatedly flushed the aperture mechanism with a few ml of fresh acetone, thus removing the remainig traces of oil. After some time the acetone suddenly got a blueish tint, and I feared that some hidden plastic stuff might have been damaged - but luckily that was not the case: The color simply came for the laquer which had been used to lock the screws of the aperture mechanim ...!

Here's the aperture mecanism after a thorough cleaning - it's completely dry (no traces of oils), and snappy. The reddish-brown dots visibly here are NOT rust; it's simply a slight coloration which looks far more dramatic on the images than it is in reality:
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The lens as it is now ...

Last thing is the rear element: Someone clearly had f***ed with it before, trying to open and clean it. I tried as well, and failed, too - even after applying acetone for quite some time. I assume it's epoxied, and since there fogging in there was quite limited (just slight fogging along the outer rims of the lenses) I left it as it was.

Reassembling was pretty easy - apart from one thing: The spring actuating the aperture mechanism was a bit tricky to re-mount.

I spent maybe five or ten minutes before I finally succeeded, using a very slim (0.7mm) screwdriver to pull one end of the spring onto the top of the screw, and a second small screwdriver to push that end over the top into its final and correct position.

OK, so much for today! - It took me about tree hours, and there were no major hiccups (apart from the rear element I couldn't disassemble).

Hopefully that's useful for others - otherwise it might just be fun to read and look at!

S