N90S/F90X: Cracked Polycarbonate Prism Covers--a baked-in problem?

[gary_watson]

Shopping for a used F90X, I've noticed many examples with fine cracks

in their prism covers that run from the screws under the Nikon logo

up toward the flash shoe.Is this a common problem? Any clues

regarding cause/prevention? Some tell me these small fractures result

from repeated impact to a camera-mounted flash. As usual, thanks.

[shawn_rahman]

Gary,

 

I bought a used N90S about four years ago, and have used it heavily with camera mounted flash, and I do not have crack in the prism.

 

Repeated "impact"? I imagine that will do it, but the prism should not crack by repeated mounting and taking off the flash. Perhaps the prism itself isn't the strongest material, but the cracks sound like they were from rough usage.

 

This is a great camera, and very inexpensive nowadays in the used market. Good luck.

[Michael R Freeman]

I don't know what causes it, but it is a very common problem with the N90s/F90X series.

[bryan_lardizabal]

Hmmmm.....Gary you may have something there, here is a photo of my camera with a

mysterious chip as you described. I don't believe I subjected the prism area to an

impact in, what seems to be an impossible area to strike if a lens is mounted...<div></div>

[bryan_lardizabal]

Smaller image

[richard_laepple]

I had two F-801s and a F4 with cracks near the screws. Both models have magnesium tops. I doubt that magnesium alloy is better than high quality plastic. Doesn't the F90 have a magnesium alloy top too? I think the reason of these cracks are impacts or tensions caused by the screws or temperature changes. After some years the material has lost its flexibility and it cracks. This never happens to the brass housings of a F, F2, F3,... But brass is too expensive today. To fix one of my F-801s I used a special metal adhesive, it worked. I hope my D70 polycarbonate is more restitant then Nikon's magnesium alloys.

[kelvin_nash]

Bryan, I have the same issue on my N90s. I have two chips of that nature in same size and distance from each edge. I must say that my camera is handled pretty roughly. It works like a charm however. I figured my problem was due to rough handling, and not much else.

 

Kelvin

[markp]

The hairline crack issue in the N90s prism, with "twin" hairline cracks originating from the two screws below the Nikon logo on the prism, is common with the N90s and F90x bodies. When the N90s was new, this issue was widely discussed on the Nikon e-mail lists. I owned two N90s's with such cracks; still have one.

 

Nikon USA never acknowledged it as a design problem, but I recall hearing from some Canadian email listmembers that Nikon Canada replaced would replace N90s top deck assemblies under warranty, and attributed the cracks to over-tightening of the two screws at the factory. I knew several people who used jewelers screwdrivers to slightly loosen the screws to prevent the problem from occurring on their cameras.

 

It doesn't represent impact with a speedlight attached, but at the time most of the listmembers I communicated with attributed it to simply the force of sliding a speedlight in and out of the hotshoe; the high torque of those screws thus caused the plastic to crack.

 

Both of my N90s's developed the problem when about a year old, though they were never subjected to impact. However, once the cracks were present and about .5-.7cm long, they never worsened and cause no functional problems.

 

I've never seen the full-out holes in the prism as pictured above. That's ugly! But, seems some electrical tape would be all that's necessary.

 

Oh, Liang-Wu Cai had a FAQ on the N90s in the '90s, which briefly discusses the prism crack issue. The page hasn't been updated in years but it is still active:

 

http://web.mit.edu/cai/www/nikon/N90sFAQ.html

 

Cheers,

Mark

[gary_watson]

Many thanks to all who kindly responded.I also tend to discount the "speedlight abuse" theory. The overtorque explanation makes much more sense, since these patterned fractures appear prevalent among both "beaters" and lightly used examples.

[jon_snape]

I've had my f90 from new, eleven years, it's never had its focusing screen changed and never had a 'pronged' nikkor fitted or been dropped, however it has the 'chips', they must be stress cracks caused by a design fault, they appeared for no apparent reason about five years ago, doesn't seem to effect the camera though so ignore it.