A few weeks ago I got this Sony / Zeiss ZA 2.8/24-70mm lens from my favourite local photo store. Its zoom ring was jammed at about f=26mm, but otherwise it seemed pretty much OK. There was no obvious damage visible on the outside, the AF motor was working, and the aperture mechanism was OK as well. I did have a similar problem in 2018 with my second ZA 2.8/16–35mm (the first one had been stolen back in 2009), but before I could dismantle that second (jammed) copy, it was stolen as well – in Rome, inside a church!

Back to this beautiful Zeiss monster. The ZA 2.8/24-70mm can be disassembled from the front as well as from the rear. Front disassembly however should be avoided if nothing is wrong with the optics. 

Removing the rear light shield barrel

Bayonet removed:

Back adjustment washers removed (shims for adjusting the distance between the lens and the camera)

The friction spring came off unintentionally when slightly uplifting the rear outer barrel assembly:

Rear outer barrel assembly removed:

Now the supersonic wave motor control electronics become visible:

Polyimide sheet removed and three connectors disconnected:

Here are a few images of those tiny connectors:

This one is about five millimeters in size; it central part may measure about three millimeters. We have fifteen conncting spikes which means they are about 100 - 150 um apart (0.1 - 0.15 mm). Inserting the flexible conductor is a bit tricky, and you have to be really precise.

 One connector (soldered) remains for time being: I was hoping it wouldn't be necessary to de-solder it, but that was futile ...

Zoom barrel rubber removed:

Now it becomes obvious that the zoom linkate plate has become loose. Sorry about the lousy image; it's the shiny silver metal part close to the screwdriver (on the left of the screwdriver). Re-mounting it doesn't solve the problem (obviously it had become loose as a result of futile forceful trials to turn the bocked zoom ring; fortunately no additional damage had been done):

To remove the Zoom Barrel, we should remove first the Zoom Linkage Plate mentioned above, along with its cap. To remove the Zoom Linkage Plate, The Zoom Barrel should be in its "24mm" positioin. However, as we have seen at the beginning, it is blocked at its 26mm position, and I can't remove the Zoom Linkage Plate! Seems to be a dead end ...

Therefore I go on removing the other parts preventing the Zoom ring to come off - first is the copper colored Grund Bracket seen below the tweezers. It's just one screw to remove, but one has to be carefful not to bend those parts of the bracket going inside the lens. I took a small screwdriver, together with the tweezers (slightly tricky work; the small screwdriver to push in the lower bruises is helpful)

Now the Zoom Brush is removed - carefully check and record its position because we will need that information when re-assembling the lens!

Remember - there's still the Zoom Linkage Plate preventing me from removing the Zoom Barrel. Since I have  no other option, I now remove the screws holding the Zoom Barrel in place. Actually one the screws is missing, and I suspect that missing screws to be blocking the zoom ring ("Zoom Barrel"). After having removed the screws, I can turn the ring just enough to be able to remove the Zoom Linkage Plate. That was pure luck - if the zoom had been blocked in another position, I would have hav no way to remove the plate!

Now I can take off the zoom ring ("Zoom Barrel"):

Wneh removing the zoom ring we can see two "roller bearings" made out of rubber - they ensure smooth zooming. Be sure not to loose them, and to re-install them correctly!

A few other small things to loosen / remove before we can go on - first this one (no idea what it is for):

BE CAREFUL ABOUT THE TWO TINY WASHERS BEHIND THE SCREWS; they easily could slip into the zoom mechanism!!

Then the focus brush removed (no washers here):

Now, finally, it becomes obvious that I have to de-solder the last remaining connection to the circuit board. Once the connection is de-soldered, I can remove the entire outer barrel assembly (just in front you see the de-soldered SSW motor connectors). Also visible the rotor of the supersonic wave motor:

While working, suddenly a badly bent screw falls out of the lens barrel:

I think "cool ... problem solved now" (I had suspected a "lost screw" right when I got the lens a few weeks ago).
However, the zoom ring still doesn't turn; it remains blocked. We have to go on dismantling the lens.

Now removing the screws holding the SSW motor in its place:

SSW motor removed! The motor is on the right side, the complete optical block on the left side. It's absolutely astonishing how much stuff we have removed until now without having touched anything on the optical block! Pretty amazing.

I now can turn the zoom ring a tiny bit more, maybe from 24 mm to 28 mm, but any further movement still is blocked. I have no clue what's going on since the "bad screw" (obviously a major factor in the disaster) can't be blocking the zoom mechanism any more. The small movement between 24 mm and 28 mm is perfectly smooth; then it hits a blockage - as if there was another loose screw somewhere inside the zoom barrel.

I'm really hesitating to open the optical block, but there's no choice. We start removing the first group (=front group), by removing the large screws shown below:

Front group is removed; we now have the core of the lens with its remaining three groups moving in complicated ways while zooming. In addition to the zoomoing, there's the movement of the focusing group, induced by a lever hidden between the three cams for the three zoom groups. This optical core is pure mechanics - just beautifully machined precision mechanics. No focusing motors, no image stabilizer, no aperture motors, no position sensors, no electronics at all. Amazing! The small barrel shown below contains fourteen lenses.

Its zooming function still is limited to 24-28mm, sadly....

Font lens barrel on the left, core barrel on the right.

Before dismantling the core of the lens I decide to really carefully look at it. There are a few scratches visible indicating the bent screw had been stuck here somwhere.

There are strange black markings on its outside, which I didn't really notice at first. I'm playing around with the core, trying to zoom beyond 28mm - impossible. Applying slightly more force suddenly results in a slightly larger zoom range. After a few more minutes of fiddling around with the lens core, the zoom range has extended again. Quite suddenly I can overcome the "stiff" range (at about f=35mm). Now zooming goes freely from 35 mm to 70mm. However, the blockage at around 28-35mm remains. I am now prepared to dismantle the damn thing completely. To start with, I loosen three of the nine screws of the zoom mechanism, one in each barrel:

Now - what a surprise !! - the entire zoom range is available, perfectly smooth and without any resistance. I'm done now; we just have to reassemble everything. I'm putting back the first of the three screws, and - bummer! - the zoom mechanism is blocked again! What a crazy little beast ;)

However it doesn't take long before two tiny - i mean really tiny (< 1 mm) - plastic parts are falling out of the core:

These two tiny particles obviously have been blocking the entire zoom mechanism (and not the badly bent screw!).

I have no idea where they come from, but they look like those tiny knobs sticking out of the larger plastic parts for no obvious reason (probably related to the manufacturing process). Two of them probably have been broken off by the bent screw, end then they got stuck in the very core of the lens.

Anyway – now the problem finally was solved, and I could start reassembling the lens. Everything went surprisingly well, with two exceptions.

 One was the re-mounting of the front lens group – one really has to be very careful not to push the front lens group too far over the (inner) zoom core: Just as far as needed to mount the three screws. I did push the core a few millimeter too far into the front lens group. After that it was locked (i. e. I could not move it backwards into the correct position). I had to remove the glass element within the front group to have access from the front.

After a few minutes of fiddling with the two parts, I finally was able to slide the (inner) zoom group barrel forward, and thus remove it from the (outer) first lens group barrel.
Problem solved!

The second problem (well, it wasn't a problem actually, but I suspected it to be one) was the re-soldering of the connector on the circuit board. My soldering gun was bit too large, but nevertheless I managed to do it pretty well. Since I was afraid of shortcuts between the four connectors, I checked the resistance between them. Two combinations were OK ("infinite" reistance), the third one had ZERO ohms. OOPS. I suspected to have soldered them together, but visual control with a 10x binocular loupe did not reveal any obvious mistakes.

Nevertheless I didn't want to risk damaging my Sony DSLR cameras with the "repaired" lens. Therefore I decided to dismantle my other Sony Zeiss 2.8/24-70mm SSM (the Var II one). After a few minutes it became clear that this lens as well had "zero" resistance between soldering points 3 and 4; so I was quite confident my repaired ZA 2.8/24-70mm (I) should work. Late night testing on the A900 resulted in tack sharp image centers (wide open at f=24mm and f=70mm); landscape testing (corners) will follow as soon as possible.