IN-FIELD TUBE-HEAD REPLACEMENT PROCEDURE Introduction

IN-FIELD TUBE-HEAD REPLACEMENT PROCEDURE
Introduction
This procedure version 1.5 applies to PantOS 16 and PantOs DG
panoramic and cephalometric systems.
Three versions of Regulation Unit boards are considered:
• Model JED 25 version 05/02/2001 or earlier.
• Model JED 25 version 26/03/2002.
• Model JED 25 version 25/03/2003.
Exchanging the Tube-Head
The tube-head is supplied with cables for connection to the Power
Switching Unit (PSWU).
9
kV
FEEDBACK
mA
FEEDBACK
10
1
2
GROUND
CONNECTION
3
4
5
6
7
8
FILAMENT
SUPPLY
HIGH
VOLTAGE
SUPPLY
kV
FEEDBACK
TEMPERATURE
SENSOR
mA
FEEDBACK
The electrical points are labelled in the picture above from 1 to 10 for
reference purposes.
• Points 1 and 2 are the input to the Filament Supply circuit.
• Point 3 is the output of the kV feedback signal, relayed to point 9.
• Point 4 is the output of the mA feedback signal, relayed to point 10.
• Points 5 and 6 are the input to the High Voltage Supply.
• Point 7 is the connection to the temperature sensor.
• Point 8 is a ground connection.
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IN-FIELD TUBE-HEAD REPLACEMENT PROCEDURE
FILAMENT
SUPPLY
MICROSWITCHES
CABLES (CEPH)
POWER SWITCHING UNIT
FEEDBACK
CABLES
HIGH
VOLTAGE
SUPPLY
M 8 NUTS
COVER
HOLDER
PLASTIC
BUSHING
• Disconnect all wires from the PSWU terminal board and the ground
wire from the frame, except those of the micro-switches (Ceph model).
• Dismount the plastic bushing and pull out all cables, except the cable
connecting micro-switches of the collimator (Ceph model).
• Dismount the collimator holder from the tube-head paying attention not
to damage the wires (Ceph model) and unscrew the mounting ring.
• Remove the two M 8 nuts on the top cover and carefully detach the
tube-head. .
• Remove the cover holder by loosening the two screws.
• Move the two M 8 bolts onto the new tube-head.
• Mount and connect the new tube-head in reverse order.
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IN-FIELD TUBE-HEAD REPLACEMENT PROCEDURE
Filament Calibration
Regulation Unit JED 25 Version 05/02/2001
The Regulation Unit is the board placed above the control panel. Follow
the listed procedure:
TRIMMER
kV
RP101
TRIMMER
mA
RP103
SWITCHES
SA101
SA102
TEST
POINT
kV
GROUND
TEST
POINT
mA
Warning: wait for cooling time between one exposure and the other.
•
•
•
•
•
•
•
•
Enter Service program Number 10.
Set the anodic voltage to 70 kV and anodic current to 10 mA.
Switch to ON both switches SA101 and SA102.
Monitor the voltage to ground of kV and mA points
Tune trimmer RP103 (mA) for 6V during exposure.
Tune trimmer RP101 (kV) for 6 V during exposure.
Switch to OFF both switches SA101 and SA102.
Exit Service Program Number 10.
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IN-FIELD TUBE-HEAD REPLACEMENT PROCEDURE
Filament Calibration
Regulation Unit JED 25 Version 26/03/2002
TRIMMER
mA
RP103
GROUND
SWITCHES
SA101
TEST
POINT
mA
The Regulation Unit is the board placed above the control panel.
Warning: wait for cooling time between one exposure and the other.
•
•
•
•
•
•
•
Enter Service program Number 10.
Set the anodic voltage to 60 kV and anodic current to 10 mA.
Switch to ON both switches SA101.
Monitor the voltage to Ground and mA point
Tune trimmer RP103 (mA) for 6V during exposure.
Switch to OFF both switches SA101.
Exit Service Program Number 10.
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IN-FIELD TUBE-HEAD REPLACEMENT PROCEDURE
Filament Calibration
Regulation Unit JED 25
Version 25/03/2003 and Version 25/06/2004
TRIMMER
FDB
RP104
TEST
POINT
FDB
TRIMMER
mA
RP103
SWITCHES
SA101
GROUND
TEST
POINT
mA
The Regulation Unit is the board placed above the control panel.
Warning: wait for cooling time between one exposure and the other.
•
•
•
•
•
•
Enter Service program Number 10.
Set the anodic voltage to 60 kV and anodic current to 10 mA.
Switch to ON both switches SA101.
Monitor the voltage to Ground and mA point.
Tune trimmer RP103 (mA) for 6V during exposure.
Switch to OFF both switches SA101.
At this point, only in case this procedure is done after replacement of
either the Regulation Unit or of the Power Switching Unit (or of both of
them) calibration of the feedback signal (FDB) has to be performed:
Monitor the voltage to Ground and FDB test point.
Set the anodic voltage to 86 kV and anodic current to 10 mA.
Tune trimmer RP104 (FDB) for 10V during exposure.
• Exit Service Program Number 10.
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IN-FIELD TUBE-HEAD REPLACEMENT PROCEDURE
Alignment of the Focal Spot
• Place a phosphor screen at the centre of the receptor side and, if
mounted, remove the collimator slit for panoramic exposures.
• Mount the ball & needle phantom. On it there are two lines crossing
each other. One in direction
backward-forward (from the
column), the other from one
side to the other one. On this
last line, just externally to the
balls two needles are marking
the position of the centre of
rotation, which is on the side
of the tube-head when the
carriage is parallel to the wall.
In the picture two sharp screws are used.
• Place the rotating carriage with the tube-head exactly on one side and
the receptor on the other side (parallel to the wall).
• Shift the rotating carriage
away from the wall and align
the beam of the side lamp on
the frontal needle (in this
position the carriage should
actually be aligned with the
transverse line of the ball
phantom).
• Place a needle/sharp screw on
the centre of rotation (tubehead side, on the left in the picture)
• Make a short exposure in the dark (70 kV, 8 mA) and check where the
shade of the needle/screw is falling on the screen.
• If it is falling in the centre, the focal spot is aligned. Repeat the
procedure to verify this also on the other side by rotating the tube-head
180° and by moving the needle/sharp screw on the other centre of
rotation (the right one when the tube-head is on the right side).
• If the shade of the needle/sharp screw appears shifted, far from the
central line on the phosphor screen, loose the two bolts of the tube-head
and shift it laterally on the same direction where the shade appears
shifted. Repeat the check with X-ray and continue shifting laterally the
tube-head until correctly aligned.
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IN-FIELD TUBE-HEAD REPLACEMENT PROCEDURE
Alignment of the Collimator for Panoramic
• Once the focal spot has been centred, mount the collimator slit for
panoramic projections and apply the radiation detector (phosphor plate)
into the secondary collimation slit, the UP mark to be up.
• Shoot X-ray, by using Service Program number 10, having set 70 kV
and 8 mA. The room should be dark enough to be able to see the
marked lines. Watch the light of the beam from below the X-ray
generator, at a convenient distance and with proper radiation shielding.
Always wait for cooling time between one exposure and the other.
• Check the beam for
rotation and align it to be
vertical by loosening the
three screws around the
body of the collimator.
• The irradiated field in
vertical height must stay
between the upper and
lower lines. Align it using
the screws on the
collimator. The ceph
version has independent
vertical adjustment for
Pan Solo, Ceph AnteroPosterior and Ceph Latero-Lateral.
• The irradiated field must be symmetrical in relation to the central line
of the radiation detector. If not, a horizontal shift has to be done by
rotating the tube-head around its vertical axis, after having loosened the
two bolts on the tube-head holder.
UP
PAN SOLO
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LOOSEN TO CORRECT
HORIZONTAL SHIFT
UP
UP
PAN CEPH
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IN-FIELD TUBE-HEAD REPLACEMENT PROCEDURE
Take a picture of the ball and needle phantom to verify proper alignment.
Put a copper filter in front of the beam to reduce radiation.
This is a digital picture made with the radiographic system PantOs DG.
WARNING
When putting back both the front and back covers of the tube housing
assembly, make sure you are using the correct screws to block them from
below.
Type M4x5 with locking washer is fine.
The use of screws with sharp edges causes the perforation of the tank with
heavy oil leakage and the impossibility to run the system without
replacement of tube-head.
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