Nikon Coolscan III problems

Course

microstepping

If this was mine , I'd connect a small spring or cord with that spring to reduce its effect, but allow continued use while you obtain info & stepper/driver replacement

That is pretty much what I was going to do although since I can't see any particular reason why the anti-backlash is in one direction and not the other I was going to re-route the spring to pull the carriage the other way. That way it is assisting in the weak direction but still doing its job.

In the longer term I do need to work out what is wrong or at least see if I can get a circuit diagram of the driver board. However it is a SCSI device so there may be something to be said for cutting my losses and getting something USB based that I can use with the laptop. For electronic devices they do seem to hold their value well on the second-hand market.

Andrew

Could it be wear or dirt on the carriage or tracks, with the off centre force from the spring making it wedge in position? As the problem is in one direction only, I'd be suspecting a mechanical cause rather than electonics failure, bearing in mind the tolerances involved.

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Tciao for Now!

John.

That was my first thought but the first thing I did was to clean and re-lubricate the tracks which didn't help. Also, as noted earlier when powering up and finding the home position there is plenty of power. It is only when returning from the scan that it is so easy to stop. Hence N_Cook's suggestion about micro-stepping.

Hi Andrew,

I have the LS-2000 scanner. I had some scanning troubles with mine as well though I can't remember if screeching noises was one of the symptoms. Not only did I clean and lube the rails, I removed anything in the transport that moved and made sure nothing was sticking. I think you'll need to remove that plastic pulley shown on page 6 of your pdf and make sure that isn't sticking as well.

Good luck.

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David Farber
Los Osos, CA

Would seem to indicate nylon wheel or it's axle binding somewhere.

Looks as if it is intended to take up any slack that develops in the lead screw/nut.

HTH.

DerekG

Well, I got a chance to do some more tests at the weekend. Basically there appear to be three [1] speeds at which the carriage can move, Fast, medium or slow. It moves on rails between the front (F) and back (B) of the unit.

On power on:

F->B fast - lots of power B->F fast - to home position lots of power

On preview:

B->F medium - preview scan, lots of power F->B fast - return to home position, can be stopped with a finger

On scan: B->F slow - scanning, lots of power F->B fast - return to home position, can be stopped with a finger

So it seems that the power that the carriage has is not related to how fast it is going but how fast it has been going. These tests were all done with the spring removed so no interference on that front.

I am at a loss to see a connection between speed and power unless there is micro-stepping involved in the preview/scan which leaves the motor in a position where the return is underpowered. But what would be the root cause?

Does the team have any further ideas of where to look next?

Thanks for everyone's input.

Andrew

[1] specifically there is a range of speeds depending on the preview/scan resolution selected.

I have a Nikon Coolscan II (LS-20) film scanner that recently exhibited the same kind of behavior that your Coolscan III does--especially the inabilit y to find it's home position, screeching, and then jamming up against the f ront stop. I read this group thread with great interest and it encouraged m e to take the scanner apart again.

Several years ago, the scanner exhibited a similar problem with loud motor noises, error codes and jamming up against the front carriage stop. I read on someone's internet posting (I don't recall who it was) that this was pro bably due to the lubrication on the rails turning to "glue" and binding up carriage movement. Sure enough, this was my situation and I cleaned the gre ase (very stiff) off and applied new dry teflon lubricant. I could see that there was grease on the jackscrew the stepper motor turns to drive the car riage back and forth. But since I had not (and didn't want to) completely d isassembled the carriage mechanism, I could not get in to wipe the old grea se off. I elected instead to put some light oil on the drive screw where th e captured nut drives the carriage back and forth. I also carefully cleaned the optics (especially the mirrors) as well as I could without completely disassembling the carriage. The scanner then operated better than it had fo r years.

When the problem cropped up again recently, I was initially puzzled. There was no way the teflon lubricant could have become stiff, so after reading t his thread, I elected to disassemble the carriage completely. I found that the grease on the jack screw had hardened again and was binding up the carr iage motion. This time I cleaned it off well and applied Lubriplate All Pur pose grease that I have had good success with in other mechanisms. I cleane d the optics again and after putting it back together it works wonderfully! There is a lot of life in these scanners, it is just inhibited by the grea ses Nikon used years ago in assembly.