Disassembly of a Nikon Coolscan 4000ED film scanner.

  16 minute read  



Nikon 4000ED
Nikon 4000ED

I have owned a Nikon Coolscan 4000ED film scanner for many years. Over that time I have encountered problems with it that have required opening up the scanner to fix something. Problems I have encountered include:

  • Dust on the mirror.
  • Blown Firewire port (actually repaired by Nikon).
  • Broken scan drive mechanism.

Having a guide on how to disassemble the scanner really helps with repairs. I have used the excellent guide produced by G.Shtengel. My article is just documenting how I proceeded to take apart the scanner basically following the same approach as used in that guide.

Coolscan mirror
Coolscan mirror
This article does not cover taking out the scanner mirror and cleaning it. Cleaning the mirror in the Coolscan 4000ED is similar to cleaning the mirror in the 5000ED. Refer to the article on cleaning a Nikon Coolscan 5000ED.


Prepare a clean, well lit, work area.

I used:

  • Jeweller’s cross head screwdriver. I used a JIS 3.0mm screwdriver. Japanese equipment usually uses JIS crosshead screws and a normal Phillips or Posidrive screw driver can damage the screw head.
  • Jeweller’s flat head screwdriver.
  • A small flat head screwdriver.
  • A small Philips screwdriver.
  • A case to organise the screws that are removed from the scanner during the dismantling process
  • Giottos Rocket Blower. Used to blow dust of the mirror before cleaning.
Tools used to disassemble scanner

If the scanner’s mirror is to be cleaned then additional items are needed for that. Refer to the article on cleaning the mirror of a Nikon Coolscan 5000ED.

When doing repairs on complex equipment it pays to stay organised. These devices often have lots of different parts, secured with all types of fastenings, that need to be disassembled and reassembled correctly.

I would recommend having a tray with lots of compartments for holding screws and fastenings from each step of the disassembly. I marked each compartment with a number showing the order of the various steps the parts placed in that compartment come from.

Storage container for screws

I next recommend you take a picture of each stage of the disassembly process. Take a picture before conducting the step, and then another picture afterwards. This helps in the reassembly as you can reverse the steps you made during disassembly and see what part fits where.


Step 1: Remove Outer Case

Unplug the scanner and remove the mains and Firewire cables. Remove any film adapter. Place the scanner on a clean work surface.

Scanner placed upside down

Remove the 8 screws on the back panel that secure the cover to the scanner.

Screws at rear that secure the panel

Each of the sides can be slid back from the front panel. It is now possible to lift each cover away from the scanner body. Sometime the cover can catch the edge of the shields inside on removal.

Remove the bottom shield from the scanner frame. This shield is attached with two screws (red circles). It also has three tabs that hook into the chassis (green arrows), gently prise each tab on the shield out of the corresponding chassis slot as you remove the shield.

Shield at bottom of the scanner

Remove the top shield from the scanner frame. This shield is also attached with two screws (red circles). It also has three tabs that hook into the chassis (green arrows), gently prise each tab on the shield out of the corresponding chassis slot as you remove shield.

Shield at top of the scanner

Step 2: Remove the Power Supply

Access to the rest of the scanner’s internals is made much easier if the power supply is removed. The power supply is retained by 5 screws which should be removed.

  • A small screw attached to the mains connector on the case (purple arrow).
  • 3 medium screws attaching the power supply board to the chassis (red circles).
  • A larger screw that also attaches the power supply board to the chassis (blue circle).
Power supply board

A magnetic screw driver can help in removing the screws. Alternatively, leave the screws loose in the holes, and remove them with the power supply board as it is extracted.

Before lifting out the power supply board the power supply cable should be disconnected from the scanner main board (green arrow). After this, the plastic arm that connects the front panel button to the power supply switch should be disengaged (orange box). This can be done by lifting the power supply board slightly out of the chassis, it should then be possible to slide the lever off the power switch. After this the power supply board can be fully removed from the chassis.

Scanner with power supply and shield removed

Finally, remove the plastic isolation shield.

Step 3: Remove the Main Board

Ribbon cable connector
Ribbon cable connector

The main board of the scanner is a large PCB, covered with metal shields, attached to the left side of the scanner. Its removal involves:

  • Disconnecting Molex connectors. These can be easily removed by holding the connector body and pulling it out.
  • Disconnecting ribbon cables. These are very delicate and can be easily ripped or damaged. Before they can be removed, the locking bracket on the connector must be gently raised using the tabs at each end. A flat jewellers screwdriver inserted under the tab at each end of the bracket can help with this. Once this bracket is raised, the ribbon cable will slide out without effort.
  • Removing 5 screws.

When removing the main board it will be necessary to keep re-orientating the scanner to get access. Be careful with any loose ribbon cables when doing this. They can flap out of the chassis, get snagged on the chassis, and tear.

The first cable to be removed is the scanner head ribbon cable from the main board. Start by unscrewing the screw (red) that holds the housing that secures a ferrite bead around this cable. Remove the screw and the housing (green arrow).

Removing scan ribbon cable ferrite holder

Next, prise up the locking bracket on the main board that locks this ribbon cable in place. This is tricky and will probably require a fine flat bladed screwdriver to be inserted from the top and bottom of the scanner in turn to reach the locking bracket ends (red). Once this bracket has been raised, slide out the ribbon cable. Do not force this, it may take a number of turns to get both ends of the locking bracket raised at the same time to allow easy removal of the ribbon. Once the end of the ribbon cable has been taken out, remove the ferrite bead from the cable.

Removing scan ribbon cable from main board connector

Now, from the side with the main board, prise up the locking bracket that holds another ribbon cable (red) to the edge of the main board. Then free this ribbon cable.

Cables to be removed from side of main board

Next, remove the two cables (blue) attached to the side of the main board using Molex connectors.

On the underside of the scanner there are two ribbon cables attached to the main board. Prise up the locking bracket on each connector and remove each ribbon cable as they are released.

Ribbon cables to be removed from bottom of main board

On the top of the scanner there are three cables with Molex connectors to be removed from the main board (the PSU cable was disconnected in a previous step).

Cables to be removed from top of main board

Finally the main board can be removed from the chassis. To do this:

  • Unscrew the small screw that secures the Firewire port to the back panel (green).
  • Unscrew the 4 screws that secure the main board to the chassis (red).
Screws securing main board to chassis

Step 4: Opening up the Chassis

Remove the front panel. The front panel is held in by two plastic clips. Insert a large flat screwdriver into the securing slots, under the edge of the clip, and gently prise up to disengage. Be careful not to snap off the plastic clip by bending it back too far. Once the edge of the clip is free of the slot you should be able to gently pull the cover forward and off.

Prise off front cover

Remove the front metal shield by removing the 3 screws securing it. Make a note of the type of screws and their location as you remove them.

Remove front shield

Remove the top of the steel chassis by removing the 4 screws that attach it. One of the screws is attached to a side plate (screw not visible on the picture).

Remove top steel plate of the chassis

Take out the black plastic film chute by removing 2 screws. First free the two cables held by plastic grips on the film chute (green arrows). Then remove the 2 screws (red). The back panel will need to be gently bent away from the film chute to allow that end of the chute to become free. It should now be possible to remove the film chute.

Remove film chute

Remove the two screws to take off the steel bracket that supported the film chute. You will need to gently hold the ribbon cables out of the way to get access to one of these screws. Some origami skills will be needed to coax the bracket free of the ribbons.

Screws holding film chute support

Remove two screws that hold the film chamber. You will need to gently hold the ribbon cables out of the way to get access to these screws.

Screws holding film chamber

Now you can remove the film chamber. You may need to raise the scanner head a little. Then lift the film chamber to free it of its location dimples and slide it out to the front. You will also need to gently feed the attached ribbon cables through the aperture as you withdraw the plate.

Withdraw film chamber to the front

Remove 2 screws holding the black anodised plate. Lift it upwards, then twist at an angle, and you can withdraw by sliding it out to the front.

Remove anodised plate

Step 5: Dismantling the Film Sled

Remove the spring that tensions the imaging platform to the film sled (green). There are also two white plastic clips (red) that hold the moving imaging platform onto the film sled. Use a flat bladed screwdriver to prise them off. The imaging platform can now be removed from the film sled.

Remove imaging platform

The imaging platform has a ribbon cable attached to it that is very delicate and often rips.

Imaging platform with ribbon cable

Remove the base from the chassis. The base is retained by three screws. Once these have been removed the base is slid off sideways to clear a retaining lug at the fourth corner of the base.

Focus drive ribbon cable clip

Before the film sled is removed from the base, turn the unit upside down. Underneath is the ribbon cable that controls the focussing drive. This needs to be freed from its retaining clips. Push the end nearest the front of the scanner towards the clips until the detent in the ribbon allows that end to be lifted free from the clip. Then the ribbon can be moved in the other direction to free the other end.

Focus drive ribbon clips

Turn the unit back the right way around. Remove the spring (green) that tensions the film sled. The rails that the film sled slides on are secured by 3 metal clips. Remove the 4 screws (red) that fix these clips.

Film sled rails retaining clips

Now gently lift the film sled off the base. The focus drive ribbon cable must be fed through the aperture as the film sled is lifted off.

The base hosts the drive that moves the film sled back and forward. The worm drive is retained at one end by a small white plastic moulding secured by a screw (green arrow). If this is removed then the worm drive and its attached white plastic gear can be lifted out.

Film sled rails retaining clips


Reassembly is essentially the reverse of the disassembly process.

Step 1: Reassemble Film Sled

The first step is to offer the film sled to the base. Push the focus drive ribbon cable through the slot (red arrow) and direct it out to the side. Align the rails to approximately their correct position. Slide the film sled along the rails until the plastic moulding is in the correct position to mesh with the plastic puck on the worm drive (green arrows).

Aligning film sled with base

Now lower the film sled onto the base ensuring the rails fit into the slots for them in the base, making sure the ribbon cable is correctly feeding through the aperture in the base. Ensure the film sled moulding has engaged with the moulding on the worm gear.

Secure the rails with the clips and retaining screws. The clip at the front has a slot in it that must be aligned with the protrusion on the base.

Film sled secured to the base

Now turn the base upside down and secure the focus drive ribbon cable within its retaining clips on the base.

Focus drive ribbon clips

Reattach the spring that tensions the film sled on the rails. This spring wraps around the big plastic pulley and back again. Ensure the spring is inside the plastic guides moulded into the base.

Work the worm drive gear back and forth to ensure it drives the film sled back and forth also.

Attach the base to the chassis. One corner of the base, the one without a screw, is hooked onto a flange in the chassis. Once engaged, align the screw holes and fix with the 3 screws.

Hold the imaging platform upside down. With a rocket blower, blow some air into the mirror housing in the imaging platform to help remove any dust that might have settled there.

Lower the imaging platform onto the film sled so that the lugs on the imaging platform fit into the matching slots on the film sled. Ensure when doing this that the ribbon cable on the imaging platform lies freely out of the back with no snags or folds. Press the white plastic clips onto the imaging platform lugs to secure it. It may be necessary to wiggle the imaging platform up and down to get the clips to engage. Reattach the spring that tensions the imaging platform.

Step 2: Reassemble the Chassis

Slide the black anodised plate through the scanning platform. It will have to be inserted at an angle and when in place will sit on some locating lugs. All of the screw holes should align with the those in the scanning platform if it has been inserted in the right orientation. Use the two screws to secure it.

Insert the film chamber into the scanner platform. This can be a little tricky as the film chamber has two ribbon cables attached to it that must be fed through the scanning platform in front of the film chamber. Orientate the film chamber at 90 degrees to the scanning platform and feed the ribbon cables through the scanning platform.

Inserting ribbon cables of film chamber into scanning platform

Now, whilst gently pulling on the end of the ribbon cables to guide them, rotate and insert the film chamber into the scanning platform. The scanner head may need to be lifted a little, and the film chamber jiggled up and down slightly as it is inserted. Eventually it should locate itself on some positioning lugs. Secure it with the two screws whilst holding the ribbon cables up and out of the way.

Place the steel bracket in position feeding it through the ribbon cables and into position. Secure with two screws.

Add the black plastic film chute. The narrow end is first inserted into the door on the back plate. The the other end is settled into position on the steel plate. Secure with two screws. The two cables can be settled into the cable grips on the top of the film chute.

Reattach the top of the steel chassis. It is secured by three screws on the top, and one on the side.

Add the front metal shield. It has three screws. Make sure these are inserted in the same places as they were removed as they are not all the same.

Press fit the front panel onto the chassis. Squeezing the chassis slightly can help it pop into place.

Step 3: Insert Main Board

Attach the main board. Before doing this ensure the shield around the Firewire port is in place. Also ensure all cables are clear of where the board will be mounted. The main board is secured by 4 screws, plus an additional tiny screw at the Firewire port.

Reconnect the cables to the main board. This is essentially the reverse order of the disassembly steps described above. Remember, to insert a ribbon cable into a connector, the locking bracket must be raised, ribbon inserted into the connector, and then the bracket pushed home to lock the ribbon in place.

  • Connect the 3 Molex connectors on top edge of the main board.
  • Connect the 2 ribbon cables to the bottom edge of the main board.
  • Connect the 2 Molex connectors and small ribbon cable to the inside edge of the main board.

Connecting the scan head ribbon cable to the connector in the middle of the main board is a bit more complicated.

  • Place the scanner on a surface so that the connector is facing upwards.
  • Ensure the security bracket of this connector is in the raised unlocked position.
  • Slip the ferrite bead onto the end of the ribbon cable.
  • Slide the end of the ribbon cable into the connector ensuring the ferrite bead stays in place.
  • Push down the locking bracket to lock the ribbon cable in place.
  • Turn the scanner the right way up. Slide the ferrite bead away from the connector and ensure the ribbon cable is correctly inserted into the connector and fully locked.
Scan head ribbon cable locked into main board connector

The next operation is fiddly. The cover for the ferrite bead must be placed over it and secured to the frame with a screw.

  • Turn the scanner the right way up.
  • Locate the ferrite bead on the ribbon cable in the position it will need to be in when clamped.
  • Place the retaining screw into the hole in the ferrite bead holder.
  • Push the holder over the ferrite bead.
  • With the screwdriver inserted through the top of the scanner locate the screwdriver into the screw head.
  • Use the screwdriver to help you locate the screw over the correct hole in the frame. Then tighten the screw.

Step 4: Insert Power Supply

Place the scanner so that the hole that will accept the power supply board is facing upwards.

Insert the plastic power supply isolation shield into this hole. It must be orientated so that its side cutout aligns with the hole in the chassis for the mains connector. The shield should rest on two metal lugs below, with the power supply screw mounting points above the base of the shield.

Power supply isolation shield in position

Drop the power supply board into the shield. Locate the mains power connector in the hole in the back panel and engage the power switch with the plastic lever from the on/off button. Secure the board with 4 screws, one of which is larger than the rest. Then secure the mains power connector to the back panel with another screw. Connect the Molex power supply cable to the main board.

Step 5: Close Up the Outer Case

Fix the two metal shields to the top and bottom of the chassis.

  • Check the attachment points of each shield to work out what goes where.
  • Insert the 3 metal tabs in each shield into the matching slots in the chassis. You will need to gently flex the shield to locate the last tab in place.
  • Secure each shield with the screws.

Place the two case sides onto the chassis. The side with holes on the main face will cover the side of the chassis with the power supply exposed.

  • Orientate the scanner so that one side is facing up.
  • Push the appropriate case side vertically down onto the chassis so that there is about a 5mm gap at the front. You may need to flex the sides of the case outwards slightly to clear the metal shields on the chassis.
  • Once fully down, slide the case side forwards to locate under the front panel.
  • Secure the case side with 4 screws at the rear.

That’s it! Attach the mains power supply. Connect the scanner to your computer. Insert an appropriate film adapter. Switch on and test with a scan of something.