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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Nikon Coolscan III problems
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 |
#2
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Nikon Coolscan III problems
You can't ignore the screeching noise. It's screeching for a reason. I'd
start by trying to track down the cause. Do you have an ultrasonic microphone? |
#3
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Nikon Coolscan III problems
Andrew May wrote in message
... 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 What sets the reference position ? a slotted opto device? |
#4
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Nikon Coolscan III problems
"Andrew May" wrote in message
... On 08/02/2012 15:30, William Sommerwerck wrote: You can't ignore the screeching noise. It's screeching for a reason. I'd start by trying to track down the cause. What I am at a loss to explain at the moment is why it can move through that position when starting up but not after focussing. That might be an important clue. But find out why it's squealing. |
#6
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Nikon Coolscan III problems
On 08/02/2012 17:02, Brian Gaff wrote:
How does this carriage know its relative position, and I suspect if the drive is slipping its somewhere in that drive and thus the slippage is misaligning the sensor. Brian 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. 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. Andrew |
#7
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Nikon Coolscan III problems
On 08/02/2012 15:30, William Sommerwerck wrote:
You can't ignore the screeching noise. It's screeching for a reason. I'd start by trying to track down the cause. Do you have an ultrasonic microphone? Unfortunately not. What I am at a loss to explain at the moment is why it can move through that position when starting up but not after focussing. Andrew |
#8
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Nikon Coolscan III problems
On 08/02/2012 17:09, Andrew May wrote:
On 08/02/2012 17:02, Brian Gaff wrote: How does this carriage know its relative position, and I suspect if the drive is slipping its somewhere in that drive and thus the slippage is misaligning the sensor. Brian 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. 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. Andrew Perhaps I should add, if I haven't mentioned it before that this is a screw drive not a belt drive. So no belt to slip. |
#9
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Nikon Coolscan III problems
Andrew May wrote:
On 08/02/2012 17:09, Andrew May wrote: On 08/02/2012 17:02, Brian Gaff wrote: How does this carriage know its relative position, and I suspect if the drive is slipping its somewhere in that drive and thus the slippage is misaligning the sensor. Brian 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. 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. Andrew Perhaps I should add, if I haven't mentioned it before that this is a screw drive not a belt drive. So no belt to slip. is it a twin screw? I've seen nasty problems with a laser cutter when one belt on one side slipped a cog and the whole thing went out of square - putting a BIG strain on the whole mechanism. |
#10
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Nikon Coolscan III problems
....snip...
Check if there is a tiny microswitch somewhere. I've recently seen a bluray drive which did something similar because a microswitch, which was activated by the movement of the carriage, got stuck. The mechanism used this to set its initial alignment and so the carriage thought it was "fully forward so need to move back" when it was actually fully back with the motor squealing because it could not move the carriage any further. As others have hinted, dust in/on an optical sensor or other sensor-knacking could be causing the same effect. Paul DS. |
#11
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Nikon Coolscan III problems
In article , Andrew May
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. -- (\__/) (='.'=) (")_(") |
#12
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Nikon Coolscan III problems
On 09/02/2012 13:45, Mike Tomlinson wrote:
In , Andrew May 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-scan...2000-cleaning/ Note: that this is the LS-2000 but the mechanism looks almost identical. Andrew |
#13
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Nikon Coolscan III problems
On 09/02/2012 14:18, Andrew May wrote:
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-scan...2000-cleaning/ Note: that this is the LS-2000 but the mechanism looks almost identical. Andrew Sorry, wrong link. It is in the second photo on that page or on page six of this document which does shoe the LS-30: http://www.vad1.com/photo/dirty-scanner/nikon-ls-2000-lubrication-guide.pdf |
#14
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Nikon Coolscan III problems
Andrew May wrote:
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-scan...2000-cleaning/ Note: that this is the LS-2000 but the mechanism looks almost identical. I would guess it's there to remove any free play in the drive system. That is, make sure that the there's no microscopic movement caused by there being no loading on the gears at any point. (There's a proper technical term for this but I'm darned if I can remember what it is at the moment. Whiplash maybe) Tim |
#15
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Nikon Coolscan III problems
On 09/02/2012 14:34, Tim Downie wrote:
Andrew May wrote: 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-scan...2000-cleaning/ Note: that this is the LS-2000 but the mechanism looks almost identical. I would guess it's there to remove any free play in the drive system. That is, make sure that the there's no microscopic movement caused by there being no loading on the gears at any point. (There's a proper technical term for this but I'm darned if I can remember what it is at the moment. Whiplash maybe) Tim That would make sense and would explain why it is not particularly strong - just strong enough to keep the carriage on one edge of the screw. I can't imagine it being strong enough to impede the carriage if it is tensioned too much so I will look at something interfering with its movement. Andrew |
#16
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Nikon Coolscan III problems
In article , Tim Downie
writes (There's a proper technical term for this but I'm darned if I can remember what it is at the moment. Whiplash maybe) Backlash. -- (\__/) (='.'=) (")_(") |
#17
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Nikon Coolscan III problems
Mike Tomlinson wrote:
In article , Tim Downie writes (There's a proper technical term for this but I'm darned if I can remember what it is at the moment. Whiplash maybe) Backlash. Ta. Tim |
#18
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Nikon Coolscan III problems
Andrew May wrote in message
... On 09/02/2012 14:34, Tim Downie wrote: Andrew May wrote: 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-scan...2000-cleaning/ Note: that this is the LS-2000 but the mechanism looks almost identical. I would guess it's there to remove any free play in the drive system. That is, make sure that the there's no microscopic movement caused by there being no loading on the gears at any point. (There's a proper technical term for this but I'm darned if I can remember what it is at the moment. Whiplash maybe) Tim That would make sense and would explain why it is not particularly strong - just strong enough to keep the carriage on one edge of the screw. I can't imagine it being strong enough to impede the carriage if it is tensioned too much so I will look at something interfering with its movement. Andrew 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 |
#19
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Nikon Coolscan III problems
Tim Downie wrote:
Andrew May wrote: 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-scan...2000-cleaning/ Note: that this is the LS-2000 but the mechanism looks almost identical. I would guess it's there to remove any free play in the drive system. That is, make sure that the there's no microscopic movement caused by there being no loading on the gears at any point. (There's a proper technical term for this but I'm darned if I can remember what it is at the moment. Whiplash maybe) Tim backlash, or simply lash. |
#20
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Nikon Coolscan III problems
On Thu, 09 Feb 2012 14:18:20 +0000, Andrew May
wrote: On 09/02/2012 13:45, Mike Tomlinson wrote: In , Andrew May 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-scan...2000-cleaning/ Note: that this is the LS-2000 but the mechanism looks almost identical. Andrew Greetings Andrew, The sound most likely is coming from the stepper. Stepper motors will squeal when stalled and driven with a microstepping driver. I would check to see if the motor can't spin when it starts to squeal. Maybe when the noise starts turn off the power and try to spin the motor shaft or move whatever is supposed to be moving. I wouldn't be surprised if you find the thing being jammed in one direction only. Eric |
#21
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Nikon Coolscan III problems
En el artículo , Andrew May
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? -- (\_/) (='.'=) (")_(") |
#22
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Nikon Coolscan III problems
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 |
#23
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Nikon Coolscan III problems
Andrew May wrote in message
... 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 |
#24
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Nikon Coolscan III problems
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 |
#25
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Nikon Coolscan III problems
N_Cook wrote:
Andrew May wrote in message ... 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. |
#26
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Nikon Coolscan III problems
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. |
#27
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Nikon Coolscan III problems
Andrew May wrote:
On 09/02/2012 13:45, Mike Tomlinson wrote: In , Andrew May 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-scan...2000-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 |
#28
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Nikon Coolscan III problems
On 09/02/12 14:18, Andrew May wrote:
On 09/02/2012 13:45, Mike Tomlinson wrote: In , Andrew May 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-scan...2000-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 |
#29
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Nikon Coolscan III problems
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. |
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Nikon Coolscan III problems
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. |
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