Repair options for a 200-400mm F/4G VR (first gen, red VR text)

[Macro_Cosmos]

Hi there,

I have one of these, the focus no longer works.
I can rotate the focus ring, however, the scale indicator will not change.  I cannot focus the lens at all.  No autofocus, no manual focus.  The focus scale window shows that the lens is stuck at around 15m.
Considering how bad the 200-400 lenses perform at far distances, this might not be too bad.  Does it produce good images at around the 15m mark? 

Here is an informative link I found: https://www.dpreview.com/forums/threads/repairing-replacing-a-200-400mm-vr1.4595309/

The author has the same issue.  The lens can be zoomed in and out, but it does not focus at all.  The motor appears to be fully functional.
As the author claims:

They looked at the lens and said they couldn't repair it due to lack of replacement parts; it apparently was not the SWM, but an internal "dent". I've no idea how it became damaged. Any ideas?

I contacted a camera repair shop in China selling some SWM motors for this lens. 
They told me that:
- Forget it, the SWM works but the lens barrel has issues, it cannot be repaired
- We will not touch it

The lens has its hood, the filter insert and the tripod foot.  I paid $350 for it.  If I sell all of these parts, I will be able to get most of my money back and keep the heavy doorstopper.
I can probably profit if I sell the functional SWM motor, they run for $200-400.

What are the options?
1. I can wait for a unit that focuses badly to salvage the so called "barrel" that is causing focus issues.
2. Just sell it for parts.
3. Adapt to Z-mount with a focusing helicoid, maybe that can work a bit.
The problem with #3 is its focusing mechanism.  If the lens moves various internal groups to achieve focus, then the third option will probably not work, or produce bad results.
I have the repair manual.  The manual focus coupling makes no sense to me.  I cannot see how "barrel problem" can cause both manual and autofocus to not work.  This seemed like a design flaw.
(Page 32: https://elektrotanya.com/nikon_af-s_vr_zoom-nikkor_ed_200-400mm_f4g_if_jaa78751_sm.pdf/download.html)
It appears that the SWM is coupled to the barrel via a "swm connecting plate".  The SWM rotates, engaging this plate to perform focusing.  If some linkage inside gets damaged, I suppose that is how we can arrive at a situation where neither focusing works.  This also means I can simply replicate the part in CAD and make one with a CNC.

Both 200-400mm lenses feature a front protective glass window.  Has anyone tried to remove it to see if the images improve? 

[Macro_Cosmos]

I found another lead.

其中200-400一二代比较特殊，有镜筒受潮膨胀的故障，表现为手动自动双失效，也可以不换件维修

They are saying the 200-400 VR first and second versions both suffer from this kind of problem.  The barrel expands due to humidity, and it causes both focusing to fail.
(... How?!  I know Nikon's microscopes have these types of insane expansion problems.  Okay maybe I just answered my own question.)

I just had a chat with the seller.  He told me it can be mitigated by trimming the barrel.  The issue was due to bad quality casts using impure aluminium, which causes it to expand when subjected to humidity.  This leads to a total breakdown of manual and autofocus.
I will send the lens to him and report back.  $600 in total for a functional 200-400 is not that bad in my opinion.

[senecaman]

Macro-Cosmos

I had exactly the same problem with my 200-400mm lens. I only discovered it after having stored the lens for a year during covid. 

None of the repair shops here in the UK would touch it.

In the end I sent it to Nikon who said it was now obsolete since spares were no longer available. They offered to scrap it in exchange for a 20% discount off a new product.

A huge disappointment on such an expensive lens.

My 300mm f2.8 VRII suffered the same problem, but that was repairable at the time with a new SWM (at high cost)

Unfortunately many of our older lenses are falling into the obsolete category as specific spares become unavailable.

[MILLIREHM]

Looks like a common problem. I was affected too. Bought mine (also version I)  in 2009 as second hand (still payed 4600 Euro then).  Later had it serviced by Nikon and got a SWM motor replacement installed. Finally a few years ago after seeing very little use and thus resting for some month I detected that it could nearly not be focussed any more. After sending it to NikonGermany again I got the reply that it needed a new inner focusing helicoid but that is not availabe any more. Finally I got it back having lost the little remaining ability to be manually focussed.

The lens was a revolutionary internal supertele-zoom with constant maximum aperture when it came out (and little to none none of the manifold "non-Pro" supertele-Zooms were available then) had great close-up capability and performed well in low to medium ranges but was found out to be subpar at longer distances. I dont need it any more but I share the disappointment that an expensive lens like that cannot be brought into life any more. It is the only lens of many I own that became unusable.

[Les Olson]

My suggestion would be to put an extension ring (the longest you have) between the lens and the camera, then see if you can focus at short distances using the zoom ring.

The basis of the test is the lens conjugate equation: 1/f = 1/u + 1/v, where f is focal length, and v is the distance behind the lens where an object at distance u is sharply imaged. If u is really big (infinity, as you might say, blushing slightly) 1/u is really small or zero, and 1/f = 1/u, meaning an object at "infinity" is sharply focused on a sensor the focal length behind the lens. To focus closer - to make u smaller - you need to make v bigger - move the lens away from the sensor. In the large format world you use the bellows to move the lens, but in the 35mm world that is done by moving lens elements around. But there is an alternative way of focussing closer: change f. If f is smaller, 1/f is bigger, then for the same 1/v, 1/u is bigger and u is smaller.

If you can focus using the zoom ring, the lens elements are where they should be and moving as they should.


The reason to use an extension ring is that the smaller u is, the bigger 1/u is, so the bigger the change in f to make 1/f = 1/u + 1/v, so it is easier if you di it at close focus.