Colortrac 3 Series User manual

SERVICE MANUAL
for
COLORTRAC LARGE FORMAT SCANNERS
models
380 Gx Plus, 360 Gx Plus and 340 Gx Plus
380 Cx and 360 Cx
Raising Lid Option

Colortrac Service Manual – Colortrac Series 3 Colour Document Scanners
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Revision11.0
© Colortrac 1997
This document should not be copied without prior permission from:
Colortrac Ltd
Kings Hall
St. Ives Business Park
St. Ives
Huntingdon
Cambridgeshire
PE17 4WY
United Kingdom
Tel: [phone]
Fax: [phone]
Colortrac Ltd makes no warranty with respect to this documentation and disclaims any implied warranties of merchantability or fitness for a
particular purpose. Information in this document is subject to change without notice. Colortrac Ltd assumes no responsibility for errors that may
appear in this document.

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CONTENTS
1. INTRODUCTION 5
2. SAFETY REQUIREMENTS 6
3. SYSTEM DESCRIPTION 7
3.1 Scanning Principles 7
3.2 Adjustments Associated With Scanning 8
3.3 System Diagram 12
3.4 Camera boards 13
3.5 Digital Board 14
3.6 Display Board /Paper Sensor 16
3.7 Ballast System /light Sensors 16
3.8 Data Rates / Volumes (Doc 8) 16
4. ASSEMBLY DESCRIPTION 17
4.1 Replacing the Digital Board 18
4.2 Changing Cameras 18
4.3 Replace both fluorescent tubes 18
4.4 Replace the glass 18
4.5 Replace the paper holdown 18
4.6 Lubricate the reduction gear. 19
4.7 Set-up & Test Procedure for Raising Lid. 19
4.8 Glass Height. 20
5. PASSWORDS 21
6. CALIBRATION PROCEDURES 22
6.1 Focus Adjustment 22
6.2 4. Magnification Adjustment 24
6.3 String Adjustment 26
6.4 Stitch 30

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6.5 Light Level Adjustment 32
6.6 Motor Speed Adjustment 32
6.7 Calibration 32
6.8 Downloading Firmware 32
7. MAINTENANCE 33
8. FAULT FINDING 34
9. WARM UP AND CALIBRATION SEQUENCES 35
9.1 Warm up sequence 35
9.2 Calibration sequence 35
10. TOOL REQUIREMENTS 36
11. RECOMMENDED SPARES 37
12. SPARES LIST 38

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1. INTRODUCTION
This manual contains the information required to service and repair a Colortrac Series 3 colour
scanner. It does not cover specification, installation, operation or operators safety as these are
covered in the installation and operating manual.
There are five different variance of the series 3 scanner which are:
Scanner
Type Maximum Resolution Optical Resolution Mode No Of Cameras Scan Width
380Gx+ 800 400 RGB 3 100cm
360Gx+ 600 400 RGB 3 100cm
340Gx+ 400 400 RGB 3 100cm
380Cx 800 400 8 bit
Palette 3 100cm
360Cx 600 300 8bit
Palette 2 88.9cm
360Gx
junior 600 300 RGB 2 88.9cm
The service manual assumes that the scanner is a 380 GX plus is being serviced. The physical
difference between the the camera models is a hardware dongle on the digital board.
The effect of changing the number of cameras also has an impact on the cables to the cameras and
the camera lenses.

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2. SAFETY REQUIREMENTS
Electrical Safety warning.
Do not remove any of the cover panels without disconnecting the power. It is important not to
remove the two power supply boards until they have been left off for at least half an hour.

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3. SYSTEM DESCRIPTION
This section covers the basic principle behind the Colortrac scanners and the main electronic
components that carry out this operation.
3.1 Scanning Principles
The heart of the scanner is a Charged Coupled Device (CCD) which is an electronic component that
converts light into voltage. Each CCD has three rows of light sensitive cells which are focused onto
a line of the image that is being scanned. The image is then moved in order to build up a two
dimensional picture.
The construction of the CCD is shown below and show that each of the CCDs rows is sensitive to a
different colour light. The information can then be used to build up a colour image.
Each light sensitive cell is 8 um by 8 um and there is a separation of 8 pixels between each of the
colours. The total number of pixels in a row is 5363. Since the scan width of the 380 model is 1000
mm ( 39.375”) and the optical resolution is 400dpi, the number of pixel required is 15750.
Therefore in the 380 models, three CCDS are used to build up the image. The optical resolution in
the 360 model has been reduced to 300 dpi and therefore only two cameras are required
Red Green Blue
8 pixels 8 pixels
64 um 64um
5363 pixels
42.9mm
Paper Direction

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3.2 Adjustments Associated With Scanning
The Colortrac scanner produces a high quality scan which requires compensation for a number of
inherent problems. These adjustments are as follows:
Left / Right Stitch
Front / back Stitch
Magnification and Focus
Light and Dark Normalisation
Colour delay Compensation
The Left / Right Stitch and Front back stitch are adjusted both electronically and mechanically. The
magnification and focus are purely mechanical adjustment where as the Normalisation and colour
compensation is completely electronic.
The exact methods of carrying out these are described in the calibration section of this manual.
3.2.1 Left / Right Stitch
The scanner contains three cameras which are mounted along the line of scan. These three camera
have got to be adjusted to ensure that there is not a gap or overlap in a scan as illustrated in the
diagram below.
Scan Line
L/R Stitch
Mag
Focus
Camera 1 Camera 2 Camera 3
The adjustment is carried out in two ways. The camera are mechanically adjusted to ensure that
there is sufficient overlap between the cameras. The total number of pixels in a camera is 5363 but
only 5250 pixels are used. This allows us select electronically which pixels are used and therefore
effectively move the image electronically. This allows the image to be joined to within a pixel. The
“ 113” Pixels of adjustment represents 0.25” of adjustment.

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3.2.2 Front / Back Stitch
The front / back stitch is carried out in order to align the three camera along the line of scan. This is
initially carried by aligning each camera to a string that is stretch across the top of the scanner. This
adjustment is sufficiently accurate to ensure that the electronic adjustment can align the camera
within a line. For each electronic line of adjustment a complete scan line has to be store in memory.
This means that there is only sufficient memory to store fourteen scan lines which gives of 0.035”
adjustment. Therefore it is critical to set this adjustment up carefully.
3.2.3 Magnification / Focus
The resolution of the scan in the X direction is set up by the magnification. This is adjusted by
moving the CCD and Lens up or down. As the Lens and camera assembly are dropped the area that
is covered by a single CCD is increased which effectively reduces the magnification.
Obviously if the distance between the lens and the scan line is moved then the system will be out of
focus. The focus is adjusted by changing the distance between the CCD and the lens. This also
effects magnification.
The passage above described the how the magnification is set in the X direction, focus is set for
both the X and Y axis, however the magnification in the Y axis is set by motor speed. The faster the
motor goes the lower the resolution. The motor speed can be adjusted to compensate for any
variation in the systems. ( The MT8 test is used in the factory to calculate the motor speed)
3.2.4 Light Normalisation, Dark Normalisation and Brightness Adjust
Dark normalisation is an automatic process that takes in account variation in the CCD output when
there is no light falling on it.
The light Normalisation ensures that that for an even distribution of light across the scan line the
voltage produced by the CCD is constant. output. This is required because there are a number of
factors that effect the response of the CCDs. The light passes through a lens which effects the
distribution of light falling on the CCD. The CCD does not respond in a linear fashion across it
length. These two effects are illustrated in the diagrams bellow.

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Lens Intensity Fall Off
Intensity
100%
70%
Centre Xdisplacement
Raw CCD Data
Volts
Pixels

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The result is that for a constant intensity of light across the scan line the voltage out from the CCD
is not constant.
Un-normalised Video O/P
Voltage
Pixels
The electronics on the camera board produces a gain compensation for each pixel to adjust for the
effects of the lens and of the CCD. This results in normalised video as shown in the diagram. These
factors are only calculated during factory normalisation and are stored in flash memory.
Normalised Video
Voltage
Pixels
Finally when the scanner is powered up and before each scan that does not have paper in the scan
line, an overall light compensation occurs. This measures the average light level across all the pixels
and then adjusts the overall gain accordingly.

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3.2.5 Colour Compensation
The CCD is made up of three lines of cells, each line responding to a different colour. Each of the
CCD lines focuses on a different scan line. Therefore it is necessary to delay the blue pixels by 16
lines, the green pixels by eight and the red pixels are not delayed. Obviously this delay is carried out
electronically and is carried out on the digital board.
3.3 System Diagram
The drawing below shows the complete scanner system. Each component is described in detail in
the section that follows.
Camera 3 Digital Board
Camera 2
Camera 1 &
Terminator
Display
Board
Paper
Sensors Paper Sensors
SCSI
Interface
Stepper
Motor
Tube
Ballast Board
Light
Sensors
Tube
Digital
PSU
Mains
Switch
/
Fuse
Mains
Inlet
The main part of the system is the digital board, it process all the data that comes from the cameras
and passes it out through the SCSI ports. It passes status information to the Display board and
receives Paper sensor position and key data back. The digital board also drives the stepper motor
and turns the lamps on and off. It is power by a switch mode power supply which supplies it with
+40,+15 and +5 Volts. The camera boards contain the CCDs and supply the digital boards with
“raw RGB data”. The stepper motor drives two paper rollers which controls the motion of the paper.
The two paper sensors detect the position of the paper. The Ballast board drives the two fluorescent

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tubes in the scanner The light intensity of the tubes is controlled by the Light Sensor Board. and the
Ballast board. The power feed for both the Ballast Board and the Digital Board PSU are fused by a
thermal fuse which is part of the mains switch.
3.4 Camera boards
CCDCCD
Drive
ADC RAM
Out
p
ut
TRC
RAM
Pixel
Correction
Serial Com
The main part of the camera board is the CCD. This is the device that converts the light into
electricity. In order to do this it requires a series of clock signals. Although these signal derive from
the digital board the drivers are on the camera board. The output of the CCD is less then 2 Volts
(normally about 0.5V) at a DC offset of 6.5 Volts. The analogue amplifier circuitry removes the DC
offsets and adjust the scaling to meet the requirements of the ADC ( Analogue to digital converter).
The ADC converts the analogue signal into a digital signal and then applies the correction for dark
and light normalisation. These correction are on a pixel by pixel basis and the data is supplied from
the pixel ram. The brightness adjustment is also carried out in the ADC before the data is passed to
the TRC ram. The control of the ADC is partially carried out via a serial communication system.
During scanning it is useful to be able to increase the response of the darker pixels. This is achieved
by applying a “Gamma Curve” to the data. An example of one is shown in the diagram below:

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Gamma Correction (Doc 6)
Intensity
Out
Intensity In
Gamma >1
This transfer function is applied in the TRC ram by using the ram as a look up table. The data is
then passed to the digital board down a ribbon cable.
3.5 Digital Board
The digital board carries out most of the data manipulation. The data from all three camera arrives
at the digital board simultaneously. It is necessary to hold one complete line of data because camera
1 data must be read first, followed by camera 2 and 3. The data from each of the camera is held in
the line rams. The line rams also provide storage for the delays required for Front/Back storage.
There is sufficient memory to allow up to 7 pixel variation in the front back stitch.
The three lines of pixels on the CCD which represents the three colours are separated by eight
pixels. The blue data for any given line arrive before the green and red, and therefore it is necessary
to delay the green and blue channels by eight and sixteen lines respectively. The delays are provided
by the Green and Blue Delay Rams. The data is loaded into these rams from the Line Rams but is
de-multiplexed in the process. Initially data is taken from the Camera 1 Line Ram with the Red
data going directly to the FPGA , the Green data going to the Green Delay Ram and the Blue
channel going to the Blue Delay Ram. Then a line of data is taken from Camera 2 Line Ram and
finally data is removed from Camera 3 Line Ram. The data from both Colour Delay Rams is passed
to the FPGA.

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Line Ram
Line Ram
Line Ram
Green Delay
Blue Delay
FPGA
SCSI
Interface
Control
Ram
Palette RamDSPMicro
Buffer
Ram
Resolution
Line Delay
The FPGA (Field Programmable Gate Array) is a programmable logic device which carries out a
number of different operation. Data is passed from the control ram to the FPGA on a pixel by pixel
basis. Certain bits of the control data is used select weather a given pixel is used or not. By selecting
which pixels are used the active image from each camera can be moved left or right. This process
allows the images from all three cameras to be stitched together.
The modes of the scanner are carried out in the FPGA. Resolution control, paletting, binary and
compression modes are all carried in this device.
Variable Resolution is achieved by interpolating the levels between pixels. In this way a pixel can
be constructed which is between two pixels in a line and between lines. Data from the control ram
indicates what proportion of each of the four pixels around the desired pixel is required. The
Resolution Delay line keeps a copy of the previous line of data in order to allow this calculation to
take place.
The palette modes use the palette ram as a look up table. The Palette ram is loaded with the pallet
mapping that is required and then address with the RGB data. The output is then sent back to the
host computer.
Binary scanning is produced by setting a threshold in the FPGA which is compare with the
incoming RGB data. The process is modified when IAT (Intelligent Adaptive Thresholding) is
used. The FPGA produces an accumulation of 16 pixels and passes this to the DSP ( Digital Signal
Processor) The DSP produces a series of threshold and sends them back to the FPGA. The FPGA
compares these levels with the incoming data in order to produce the binary output.
The data from the FPGA is passed to a small buffer before being handled by the SCSI interface
circuitry and sent to the host. The buffer is not designed to hold large amounts of data but does
ensure that the scanner has sufficient time to stop if the host computer cannot cope with the data.

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The microprocessor does not carry out any of the data processing. It carries out a series of tasks that
control the data, such as loading the FPGA with its logic circuitry and setting up the various delay
lines.
3.6 Display Board /Paper Sensor
The display boards provides 3 led indicators, and two push buttons to allow for the operator
interface. The paper sensor are also connected to it. The display board contains a micro-controller
which communicates to the digital boards via a serial communication system. This communication
link is by-directional, in that the paper sensor and button push information is sent to the digital
board and the led status information is received from the digital board.
3.7 Ballast System /light Sensors
The ballast board drives the two fluorescent tubes. It has a digital input from the digital board. The
intensity of the lights is detected by a light sensor board and an analogue signal is passed to the
ballast board. This is used to control the drive to the tubes. The mains input to this board is power
factor corrected and produces an intermediate voltage of 400 volts. This is then switched and used
to drive the tubes. There is a detection circuit that ensure that both tubes are connected and that
there is not a current overload.
3.8 Data Rates / Volumes (Doc 8)
A common problem that is in understanding of file size and data rates when considering large
format scanning. Initially consider data file sizes:
Data Volume for E size sheet (42” x 32”) in 400 DPI RGB mode:
42 x 32 x 400 x 400 x 3 = 645 M bytes
This can be reduced to= 215 Mb in 256 colour/ greyscale
= 107 Mb in 16 colour
= 27Mb in binary
Compression can reduce data volumes for some drawing types
Now if dates rates are considered:
A width of 32 “ travelling at 0.75”/Sec at 400 dpi RGB mode gives a data rate of:
32 x 0.75 x 400 x 400 x 3 = 11.5 M bytes /sec
The SCSI controller maximum data rate = 15M bytes /sec and therefore can cope with the data
produced by the scanner. However most host computers are not able to store data at this speed.

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4. ASSEMBLY DESCRIPTION
Rear View of The scanner
Rear View of The scanner
Digital Board
Ballast Su
pp
l
y
Camera Board
Main PSU
Dis
p
la
y
Motor
Li
g
ht Sensor Board

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4.1 Replacing the Digital Board
When the digital board is replaced ensure that:
1. The security dongle is changed.
2. The motor speed is updated
3. The correct firmware is used.
4. The system is re-calibrated
4.2 Changing Cameras
If the cameras require changing ensure that:
1. All three cameras need to be changed
2. Camera 1 has a terminator fitted
3. Don’t forget to fit the gasket between the camera board and the camera casting
4.3 Replace both fluorescent tubes
1. Open the lid of the scanner
2. Remove the two screws that secure then end castings. Make sure that the end castings are
supported before carrying this out.
3. Disconnect the two connectors on the display board.
4. Loosen the screws that hold the brackets that lock the tubes in place.
5. Remove and replace the tubes.
6. When replacing the end castings ensure that the tube connectors are properly secured, reconnect
display board and ensure that there are no wires trapped.
4.4 Replace the glass
1. Open the lid and remove the two screws that secure the glass.
4.5 Replace the paper holdown
1. Open the lid.
2. Remove the four screws that secure the paper holdown in place.
3. The paper holdown then slides out

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4.6 Lubricate the reduction gear.
1. Open the lid
2. Remove the two screws that secure then end castings. Make sure that the end castings are
supported before carrying this out.
3. Oil the reduction gear ( The spindle that has two gears on it).
4. Ensure that when the casting is replaced, no cables are trapped and that the tube connectors are
secured
4.7 Set-up & Test Procedure for Raising Lid.
4.7.1 Latches.
The plunger should operate without excessive friction and click positively into the locked (pushed
in) position. Note that the lock pin (the one sticking out the end of the lid when the plungers are in
the locked position) should be visibly square to the end face of the lid and not fouling the end of the
slot in the lid end plates.
DO NOT LEAVE THE LID OPEN AND HANGING ON THE HINGES WITHOUT THE END
CASTINGS IN PLACE. IT CAN FALL OFF.
4.7.2 Drive Roller Nip.
These two adjustments are made by moving the rear locator blocks on their slotted holes. Do these
tests/adjustments with the lid fully assembled except for the pinch roller covers, and with the end
covers in place.
1. Check that the pinch rollers are compressed by approximately 0.5 mm. and that the compression
is equal from end to end. Close the lid slowly observing the gap between the pinch rollers and
the drive rollers. The gap should close equally.
2. There must be enough nip between the pinch rollers and the drive rollers so that the lid pops up
at the back and the extractor levers stay in the outward position. The extractors should snap back
to the inner position when the lid is pressed down against the pinch roller spring pressure.
4.7.3 Hold Down Clearance.
Close the lid and lock in the lowest position.
Using a 5.5 mm thick plastic test piece check that the Paper Hold Down lifts to clear the test piece.
The test should be applied at both ends and the middle.

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If the Paper Hold Down requires adjustment place 1 or 2 mm ‘horse shoe’ shims under the Paper
Hold Down Bracket.
4.8 Glass Height.
Set the height of the glass in relation to the top of the drive rollers such that the glass is 0 to –0.3mm
below the rollers. This test can be carried out by placing a steel rule over the rollers and checking
that there is a small amount of clearance between the ruler and the glass. If this requires adjustment
then it is carried by replacing the screw that attach the main extrusions (the extrusions that contain
the rollers) with screws that have been machined to allow adjustment (Please contact Colortrac).
The extrusions and therefore the glass can then be dropped in relationship to the rollers. The
extrusions must be kept level when this is done.