Reassembling the Coolscan IV - for HARDWARE gurus only

After two years of use,I disassembled my Coolscan IV for cleaning the

mirror, lens and

the CCD. Cleaned the lens and mirror with pre moistened lens cleaning

tissue. Was extra careful with the CCD, used only a stream of air

from a can of compressed air. When I put it all back together, it

seemed to work fine - however, there were geometrical distortions in

the scanned image from a 35mm slide. I traced the problem back to the

misaligned CCD board, and here is what I found: <p>

When the CCD PCB (printed circuit board) is moved horizonatally

(there is some play when the 2 black screws are loosened)or

vertically at right angles, it results in the cropping of the image

along one or more of the four edges. If the PCB is rotated along an

axis perpendicular to its plane, the rectangular image distorts to a

rhombus. By trial and error, ie shifting and rotating the PCB I

managed to get the image back to a rectangular shape without any

cropping along any of the edges. <p>

However there is one remaining problem. The image is now 'elongated'

along the long edge, meaning that the long edge of the scan seems to

have been stretched. However the image size is still 2870x4203. I

don't think its the CCD assembly anymore, I have tried almost

all 'degrees of freedom' with it. It could be in the LED light source

assembly, but I am not sure. It didn't seem to affect the picture in

any way. Anyone has any idea what I need to adjust/align to fix this

problem ? <p>

Nikon USA told me to send it over. I don't want to do that, I know

its some minor alignment problem somewhere, and I am sure I can do it

my self. <p>

Thanks.

<b>"I am sure I can do it my self."</b>

<p>Well, if you're so sure, why would you need to ask? Do what you should have done in the first place and let the pros handle it.

Hey Tim,

Seems unlikely that the LEDs would have anything to do with the distortion. The spatial relationship between the CCD assembly, the lenses and the film platform is important. Since you seem to have got the CCD assembly back in its general position, I'd suggest that the lenses are probably the next thing to experiment with as you probably did not touch the film stage.

Just in support about what you have done - I would have done exactly the same thing myself (ex-warranty like yours, of course!). The knowledge that you gain from knowing how the machine works puts you in a better position to solve problems with the machine, or even makes you a more appreciative user.

More than anything else, thanks for the support, Taquin. Some people will take their equipment back to the dealer(cars included) at the drop of a hat, and just beg on their knees to get robbed (eg: the first responder) Others, such as you and myself, will spend the effort on learning for themselves, save money and enjoy the rich experience of learning itself ! <p>

And here is the reward for my week long effort. I finally figured out what was causing the aspect ratio of the scanned images to change. The distance between the CCD assembly and the lens can be adjusted and it has to be exact, otherwise the magnification of the LED slit beam projected onto the CCD line sensor will be incorrect. The length of the slit beam that moves along the longer edge of the 35mm slide, corresponds to the width of the slide. This beam then passes through the lens and is focused onto the CCD sensor. The two have to be perfectly alligned. If they are not, it will cause other forms of distortions as I mentioned in my previous post. And if the distance is not right, the aspect ratios will be affected. It took me hours to callibrate everything properly. Finally, I have a scanner that I know how it works, that makes great images, saved money, and above all greatly enjoyed the whole experience.