Nikon Coolscan III problems

[Mike Tomlinson]

En el artículo <9pi2tdFtklU1@mid.individual.net>, Andrew May
<andrew_d_may@hotmail.com> escribió:

In the meantime dos anyone have any ideas about the purpose of the
spring.

It looks like it's intended to hold the scanner head in tension to
prevent movement due to any play in the mechanism. If removing it makes
the thing work it suggests the motor is weak - faulty motor or driver
transistors or possibly a power supply fault. Checked for bad
capacitors?

--
(\_/)
(='.'=)
(")_(")

 

[Andrew May]

On 09/02/2012 15:50, N_Cook wrote:

I'm just wondering if something has gone wrong with microstepping. Course
back and forth movement and then at near focus dropping into microstepping
mode and not enough drive/wrong phasing / interaction with that spring


It cold well be. I had a closer look last night and found the following

with the spring removed:

When starting up and finding the home position it will move the carriage
backwards and forwards with sufficient force that it is not possible to
easily stop it.

While scanning it moves the carriage from the rear towards the front,
basically from the home position over the slide and does this with
sufficient force that it is not easy to stop.

Having finished the scan it returns to the home position but this time
just putting a finger in the way will stop the movement and results in a
squealing sound.

What I can not figure out is, if this is a micro-stepping problem, why
it is using micro-stepping to return the carriage to the home position.
I can understand it when scanning but not when it has finished. But then
I have no experience of stepper motors.

I assume the motor is OK. Is this indicative of a problem with the drive
circuitry? I don't have a service manual or circuit diagram but the PCB
which I assume does the driving is not very large and could probably be
traced out.

Andrew

 

[N_Cook]

Andrew May <andrew_d_may@hotmail.com> wrote in message
news:9pkkouFmgfU1@mid.individual.net...

On 09/02/2012 15:50, N_Cook wrote:


I'm just wondering if something has gone wrong with microstepping.
Course
back and forth movement and then at near focus dropping into
microstepping
mode and not enough drive/wrong phasing / interaction with that spring


It cold well be. I had a closer look last night and found the following
with the spring removed:

When starting up and finding the home position it will move the carriage
backwards and forwards with sufficient force that it is not possible to
easily stop it.

While scanning it moves the carriage from the rear towards the front,
basically from the home position over the slide and does this with
sufficient force that it is not easy to stop.

Having finished the scan it returns to the home position but this time
just putting a finger in the way will stop the movement and results in a
squealing sound.

What I can not figure out is, if this is a micro-stepping problem, why
it is using micro-stepping to return the carriage to the home position.
I can understand it when scanning but not when it has finished. But then
I have no experience of stepper motors.

I assume the motor is OK. Is this indicative of a problem with the drive
circuitry? I don't have a service manual or circuit diagram but the PCB
which I assume does the driving is not very large and could probably be
traced out.

Andrew

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

 

[Andrew May]

On 10/02/2012 13:54, N_Cook wrote:

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

 

[John Williamson]

N_Cook wrote:

Andrew May <andrew_d_may@hotmail.com> wrote in message
news:9pkkouFmgfU1@mid.individual.net...
On 09/02/2012 15:50, N_Cook wrote:

I'm just wondering if something has gone wrong with microstepping.
Course
back and forth movement and then at near focus dropping into
microstepping
mode and not enough drive/wrong phasing / interaction with that spring


It cold well be. I had a closer look last night and found the following
with the spring removed:

When starting up and finding the home position it will move the carriage
backwards and forwards with sufficient force that it is not possible to
easily stop it.

While scanning it moves the carriage from the rear towards the front,
basically from the home position over the slide and does this with
sufficient force that it is not easy to stop.

Having finished the scan it returns to the home position but this time
just putting a finger in the way will stop the movement and results in a
squealing sound.

What I can not figure out is, if this is a micro-stepping problem, why
it is using micro-stepping to return the carriage to the home position.
I can understand it when scanning but not when it has finished. But then
I have no experience of stepper motors.

I assume the motor is OK. Is this indicative of a problem with the drive
circuitry? I don't have a service manual or circuit diagram but the PCB
which I assume does the driving is not very large and could probably be
traced out.

Andrew




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


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.

--
Tciao for Now!

John.

 

[Andrew May]

On 10/02/2012 14:09, John Williamson wrote:

N_Cook wrote:

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.

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.

 

[David Farber]

Andrew May wrote:

On 09/02/2012 13:45, Mike Tomlinson wrote:
In article<9pfoiuF7viU1@mid.individual.net>, Andrew May
andrew_d_may@hotmail.com> writes

As far as I can see the initial reference position is found by
moving the carriage to the back where there is possibly some
sensor, optical or otherwise.

This is known as 'homing'.

Then step back a known number of steps to achieve the
reference position. This all works fine. It is when it tries to move
back to this position after focussing that it fails to get there
and the problems ensue.

Would you say it can drive in one direction OK but not the other? If
so, the drive transistors to the stepper may be failing.


It will drive quite happily in both directions when turned on and
finding the home position. It is only when doing the scan that is
seems to stop in the backwards direction.

Other obeservation. The sound appears to come from the stepper motor
but I cannot be absolutely certain bit is seems to indicate that it
is being prevented from moving.

There is also a long spring attached to the rear end of the carriage
that goes around a wheel at the front and back to the rear of the
chassis. It is not clear what this does. It looks as if is should be
for returning the carriage but the carriage is driven in both
directions by the screw.

I have tried removing this spring and everything seems to work with it
removed. Replacing it triggers the failure again. There is no sign of
any interference between the spring and the carriage but the spring
does not move smoothly around the wheel so it may be that it is
applying too much pull on the carriage and causing it to stop. Then
when it runs forward again it lets a bit more spring out and stops it
earlier the next time.

When I get a chance tonight I will try a bit of lubrication on that
wheel to see if that helps.

In the meantime dos anyone have any ideas about the purpose of the
spring. It can be seen at the bottom of the photograph on page six of
the document here if anyone is interested.

http://www.vad1.com/photo/dirty-scanner/ls2000-cleaning/

Note: that this is the LS-2000 but the mechanism looks almost
identical.
Andrew

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.
--

David Farber
Los Osos, CA

 

[Derek Geldard]

On 09/02/12 14:18, Andrew May wrote:

On 09/02/2012 13:45, Mike Tomlinson wrote:
In article<9pfoiuF7viU1@mid.individual.net>, Andrew May
andrew_d_may@hotmail.com> writes

As far as I can see the initial reference position is found by moving
the carriage to the back where there is possibly some sensor, optical or
otherwise.

This is known as 'homing'.

Then step back a known number of steps to achieve the
reference position. This all works fine. It is when it tries to move
back to this position after focussing that it fails to get there and the
problems ensue.

Would you say it can drive in one direction OK but not the other? If
so, the drive transistors to the stepper may be failing.


It will drive quite happily in both directions when turned on and
finding the home position. It is only when doing the scan that is seems
to stop in the backwards direction.

Other obeservation. The sound appears to come from the stepper motor but
I cannot be absolutely certain bit is seems to indicate that it is being
prevented from moving.

There is also a long spring attached to the rear end of the carriage
that goes around a wheel at the front and back to the rear of the
chassis. It is not clear what this does. It looks as if is should be for
returning the carriage but the carriage is driven in both directions by
the screw.

I have tried removing this spring and everything seems to work with it
removed. Replacing it triggers the failure again. There is no sign of
any interference between the spring and the carriage but the spring does
not move smoothly around the wheel so it may be that it is applying too
much pull on the carriage and causing it to stop.

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

Then when it runs
forward again it lets a bit more spring out and stops it earlier the
next time.

When I get a chance tonight I will try a bit of lubrication on that
wheel to see if that helps.

In the meantime dos anyone have any ideas about the purpose of the
spring. It can be seen at the bottom of the photograph on page six of
the document here if anyone is interested.

http://www.vad1.com/photo/dirty-scanner/ls2000-cleaning/

Note: that this is the LS-2000 but the mechanism looks almost identical.

Andrew

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

HTH.

DerekG

 

[Andrew May]

On 11/02/2012 04:33, David Farber wrote:

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.

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.

 

[Tickerman]

On Wednesday, February 8, 2012 at 9:15:25 AM UTC-5, Andrew May wrote:

I have a Nikon Coolscan III (LS-30) film scanner that has worked
flawlessly since I purchased it new about twelve years ago. Now, however
it is giving a few problems in that the carriage appears to stick.

It operates by moving the scanning carriage forward and backwards over a
transparency or strip of film using a stepper motor. A second stopper
motor moves it in the vertical direction for focussing.

I have stripped it down and cleaned and re-lubricated the rails which
seems to be the standard maintenance procedure but to no avail.

What should happen (I think) is this. When the scanner is first turned
on it moves the carriage to the far rear and then steps it forward to
some sort of reference position located so that the sensitive parts are
out of reach when the film carrier is removed. Here it remains. There is
an autofocus function in the software that can be initiated at any time
and moves the carriage forward until it is somewhere within the frame
and performs a focus adjustment. It then returns the carriage to the
reference position. All well and good and this action can be performed
repeatedly.

What is actually happening is that in moving the carriage back to the
reference position after performing the focus it stops short by about
5mm with a short but loud screeching noise. At this point the reference
position is out by 5mm so repeating the action moves it 5mm further
forward. What is interesting is that this time it still gets pulled up
short with the same sound so now is 10mm short. I conclude it is not a
physical obstruction otherwise it would return to the same place and I
would expect it to happen on start-up as well when it is moved all the
way to the rear. Eventually after several of these focusing actions it
is so far forward that when moving forward it rams into the start of the
screw and cannot be dislodged by the stepper motor. It needs manual
intervention to turn the stepper to move the carriage back a little.
Turn off. Turn on and all moves back to the original reference position.

Before I decide whether to replace this or send it off for repair I
should like to have a go at fixing it but having tried the obvious would
appreciate some pointer towards what the problem might be.

Andrew

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 inability to find it's home position, screeching, and then jamming up against the front stop. I read this group thread with great interest and it encouraged me 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 probably 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 grease (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 carriage back and forth. But since I had not (and didn't want to) completely disassembled the carriage mechanism, I could not get in to wipe the old grease off. I elected instead to put some light oil on the drive screw where the 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 for 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 this 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 carriage motion. This time I cleaned it off well and applied Lubriplate All Purpose grease that I have had good success with in other mechanisms. I cleaned 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 greases Nikon used years ago in assembly.