Vệ Sinh Pentacon 135/2.8 (sưu tầm)

I always liked to put again in operation old devices... if someone is discarding something, I am often ready to take it with me and bring it to a new life...

This time I bought on eBay for a ridiculous price a Pentacon 135 2.8, a fully manual lens, made in German Democratic Republic in the seventies, sold 'AS IS' (that usually means in really bad shape). From the photos the lenses looked reasonably clear...

At the delivery, I made my diagnosis: stiff focus, stiff diaphragm ring, dust in between the lenses, and an horrible rattling coming from its guts... but, luckily, the splendid 15-blades iris was clean and shining.

Time for a complete overhaul...

These are the 'tools' you need for such a work, each one very common:

- A generous dose of common sense and patience (not pictured)

- A clean and tidy bench, in a room with a comfortable temperature

- Modified Seeger remover ( I simply filed the round edges, making a set of spanners! )

- Set of precision screwdrivers

- Dust blower

- Small torch

- Felt pen

- Molybdenum bisulfide grease

- High-grip mat

- A LOT of paper towels

- Soap

- Discardable toothbrush

And now let's go to the bench! [And keep always in mind there is no rush... when you feel uneasy it's time to stop (have a beer, maybe :-) ) and try to understand the meaning of the parts you are looking at...]

Phần 2:

This is the patient. Don't care about its hygienic conditions, right now. We are going to perform a complete dismantling, so we will take care of dust and crud later.

[Looking at the front lens mounting, I decided to leave it alone. It looked really hard to remove the front lens without scratching the black paint, and besides that, all the lenses I overhauled had a complete access from the rear. I know there are exceptions, but a 'rear approach' looked like the most sensible thing to do. And it proved true...]

First of all, set the diaphragm to FULL OPEN, and leave it as it is for the WHOLE process. It is important, because you don't want to risk to damage the iris.

Then unscrew the mount retainer ring. This will let the M42 mount free. All these East lenses from the seventies/eighties were sold in different mounts (M42, M39, Praktica, etc...) so the mount is almost always easily removable:

Raise the mount, noticing a small lateral slot and a matching protruding screw (its purpose is clearly to prevent a rotation of the mount when attaching the lens to the camera)...

There are three screws under the mount. Two flat and one raised (the one cited before). Unscrew all three, and place them in a safe place. And remember, from now on MARK WITH THE FELT PEN THE POSITION OF EVERY ELEMENT REMOVED. Don't forget it. We will talk about marking again, and again.

In this case we mark the position of the 'anomalous' screw, both on the external and the internal surface of this first ring. This particular marking proved unnecessary, but you NEVER know, until you loose an unrecoverable adjustment. Just mark everything you remove, and you will be glad to have done it, for sure.

Everytime you remove something, do it slowly and carefully, FEELING the part. After removing the three screws, the whole cap with the diaphragm marks can be raised. But it has a 'scratchy' feeling... because it retains TWO springs at both sides of the lens. These springs push two small pinions agains the anti-rotation groove of the focus helicoid. If the removal of the cap is too fast, the springs will fly away, following a lot of Murphy's laws (last but not least: Any object when dropped will roll into the least accessible corner).

This is the view after the removal of the previous cap. Notice one of the springs. When putting again the cap in place, you will have to gently push the springs under the cap with a small screwdriver. But now remove them, and also the pinions they push, AFTER HAVING MARKED THIS POSITION for remounting. Put them away in a safe place again. [Beware of cats... they LOVE dropping on the floor very small screws and springs. Believe me.]

Now things get a bit tough...

Phần 3:

Grasp the focus ring, and GENTLY and VERY SLOWLY turn it CLOCKWISE. After removing the anti-rotation pinions, it will begin to unscrew from the focus helicoid. At one point it will came loose. MARK WITH THE MAXIMUM PRECISION THAT POINT ON BOTH THE RING AND THE BARREL, this time making a little carving with the tip of a screwdriver (obviously not on the helicoid itself). You really DON'T WANT to miss that point. If you miss the marking you will loose focus at the infinity... and the only way to get it again would be by trial and error, dismantling and remounting the lens a number of times equal to the number of entry points in the helicoid (and they are typically A LOT)...

From now on, it's also time to clean. Remove the old grease and crud with paper towels and lighter fluid, alcohol or something like that. Take your time, and take care not to smear the exposed lenses. When the helicoid is clean, wash your hands. Then take the most suitable spanner, and VERY CAREFULLY unscrew the rear lens assembly (some force is involved... if you don't feel comfortable protect the lens with a soft cloth... but this step IS dangerous. Please be careful and DON'T SCRATCH your rear lens assembly!)

[This step is required only to thoroughly clean the rear lens assembly. If yours is not to be cleaned, leave it as it is.]

Put the lens assembly away, and DO NOT LAY IT ON A HARD SURFACE.

Now that the most exposed part of this phase is safely stored away, we can clean some more and relax a bit. The tricky parts have yet to come...

On a side, near the focus helicoid, you will find a very small hole, with the smallest screw of your life hidden inside. Unscrew it with a suitable precision screwdriver, WITHOUT TAKING IT COMPLETELY OUT. If it exits that hole, it will require an extra amount of time to be reinserted... and remember that screws of that ridiculous diameter are really easy to mangle...

Now unscrew the following 'cap' (that was retained by that very small screw):

You will find a lot of grease, here. This is because under the previous cap, the diaphragm actuator has to be lubricated to freely rotate. Clean the grease, and remember to put it there again when remounting everything.

There is a strange screw locked in a tab, here, that couples the diaphragm actuator to the actual iris. Remove it, but TAKE EXTRA CARE because there is a spring, two rings behind, tensioning the whole assembly upward. Remove the screw whilst gently pressing down the actuator.

Then gently remove the slotted actuator ring.

Another screw is exposed. It is the diaphragm stopper (it blocks the rotation at fully open and fully closed, not to damage the iris mechanism). Remove it, and remember there is a tensioning upward...

Remove the diaphragm step indicator. Under it there is a steel wire curved to act as a spring. Look at it carefully to understand how and where it is to be inserted when remounting (it slides in a circular slot, that has to be regreased).

Clean thoroughly from grease; you will find on the side another OH SO TINY screw; same as before: loosen it, but don't remove it completely. It is evident at this point that this screw inhibits the unscrewing of the front element from the helicoid. Grasp firmly the two parts, and unlock them with a bit of force.

Detach the helicoid from the front element. It requires a lot of turns... at first it looks like it is only rotating, instead of unscrewing!

Now the most fragile and soft part of the lens is exposed: this is the center lens assembly, locked in place by a conical ring. GOTCHA! This ring in my case loosened, causing that horrible rattle and a strange optical effect (because the center element was dislodged from its optimal position).

Unscrew and remove the conical ring to access the center element; to unscrew it only friction is required; it is large enough to be unscrewed with bare hands. But remember NOT TO TOUCH THE LENSES!

CAREFULLY estract the center element (it a relatively big and heavy block of optical glass... DON'T DROP IT AND DON'T LAY IT AGAINST HARD SURFACES!!!) and gently clean it and the rear of the front lens with the blower. We are at the bottom end, at last!

Place the center element back in place, and tighten the conical ring.

Now CLEAN EVERYTHING AGAIN; everything must be shining. The all-metal parts can be washed in soapy warm water, brushing them with a discardable toothbrush until perfectly clean. Then dry them thorougly, better with a not too warm hairdryer. Then it is time to remount everything, following the reverse order, and reapplying a reasonable amount of molybdenum bisulfite grease. (I choose this kind of grease because it gives a mild sensation of friction, adheres to metals, resists to heat and provides protection against oxidation, humidity and corrosion. And if it works for high load bearings, it surely works for focus helicoids...)

On the focus helicoid apply grease BY HAND in the right quantity to fill the threads, but no more than that. It will give a nice 'braking' feeling when focusing... After remounting, wipe away the excess of grease squished out. But leave a thin film on the outside rim... it acts as a barrier against dust. We don't want to have to open again the lens because some particle of dust enters the helicoid and starts scratching...

The remounting is pure boredom, if you marked everything. The only tricky part is to reinsert the focus ring; it takes a steady hand and some patience. DO NOT FORCE THE ENTERING ON THE HELICOID! When it is well aligned and parallel it will screw in like a charm.

And now let's take a look at the final result....

A wonderful 15 blades iris through a perfectly clean front lens and central element...!

Shining body, and no more rattle!

Like new! (with some minor traces of use... but it has almost 40 years!)

[ The whole process took less than two hours, not knowing the sequence or the meaning of parts... I bet you can do it in less than an hour, following my example! ]

If someone performed an overhaul of the iris, please write me an email! I will be glad to add the pictures to this 'howto'... with proper credits, obviously!

24/02/2008 - UPDATE...

I am a member of the wonderful "Manual Focus Forum", and Robin Murphy, from UK, started an interesting thread about a very similar lens, covering the iris maintenance. If interested, look at it here: Pentacon 4/200 preset aperture repair

Link: http://www.mqcvisions.net/Pentacon_135_2_8/Pentacon_1.html

0 nhận xét:

Đăng nhận xét


Liên Hệ

Liên hệ Sách Nguyễn Photography
ĐC: 98 Nguyễn Viết Xuân, T.P Vinh
ĐT: 0978877999 – 0977992282
email: sachnguyen@gmail.com

Người theo dõi

Biểu mẫu liên hệ


Email *

Thông báo *