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EN 8
4.
DPTV565 AA
4.2
Service Position
1. Remove the Side Back Covers.
2. Remove the Front Speaker Baffle.
3. Remove the Front Control Panel.
4. Route the ribbon cable and the wire through opening and
into the back of the unit.
5. Reconnect the ribbon cable to the Front Control Panel.
6. Remove the Side Jack Panel to allow room for cable
movement.
7. Remove the rear Jack Panel cover (76).
8. Being careful with the PIP Panel, pull the Chassis Frame
out and tilt up.
9. Place the Chassis Frame on the bottom board of the PTV.
4.3
Picture Tube Replacement
Replacement of the cathode ray tube (CRT) and/or optical
system components of a Projection TV (PTV) can be easily
accomplished by following general guidelines. Use care when
working around the CRT and optical systems of the PTV. The
PTV light path encompasses a number of precision optical
components. These include lenses, mirrors, the lenticular
screen, and Fresnel lens. The PTV incorporates three separate
CRTs, representing green, red, and blue outputs. Each CRT
uses an independent deflection/convergence yoke, magnetic
centring ring, coupler, C-element lens, and output lens (A/B
lens). Each tube is mechanically fastened to a coupler which
houses fluid (a glycol-type substance) used to cool the high
temperatures generated by the small (7") CRTs. The fluid also
provides an optical characteristic supporting the optical system
of the PTV. When replacement of a CRT or optical component
is required, caution must be exercised in preventing fluid
spillage. The technician must carefully reassemble the CRT/
optical components, ensuring a proper seal of the coupling
fluid. Use only factory original coupling fluid.
Caution: Do not use or add water as an alternative to the
prescribed coupling fluid.
Note: Upon completion of CRT/optical assembly repair, the
centring, convergence, grey scale, mechanical and electrical
focus adjustments are required. If more than one assembly
requires repair, it is recommended the service technician fully
complete one assembly at a time, using the existing
assemblies as a reference for the alignment of the centring and
convergence.
The following procedure should be used when performing
repairs on the CRT/optical assemblies of the Projection TV.
4.3.1
Disassembly Procedure
A. Removal of a single CRT/Lens Assembly from the light
rack
1. Remove AC power from the PTV.
2. Remove the upper and lower back covers (1/4" screws).
3. Remove the barrier board and the shield cover from around
the lens assemblies (1/4" screws).
4. Carefully remove the CRT Socket Board from the CRT of
the CRT/optical assembly being serviced.
5. Remove the yoke and convergence plugs, of the CRT/
optical assembly being serviced, from the Large Signal
Module.
6. Remove the high voltage anode lead from the HV splitter
block on the Large Signal Module of the CRT/optical
assembly being serviced. Remove ground lug connectors
from the coupler frame.
7. Remove the four 1/4" screws that secure the CRT/lens
assembly to the light rack. These four screws are located
in each corner, on the top of the coupler assembly.
Caution: Do not remove the bolts with pressure springs or
the inverted Torx screws of the CRT/lens assembly. The
Mechanical Instructions
4.3.2
removal of these components could result in fluid spillage
into the PTV cabinet.
8. Carefully remove the CRT/Lens assembly from the PTV
cabinet.
Servicing the CRT/Lens Assembly
Warning: Coupling fluid is a poisonous solution containing a
high concentration of ethylene glycol. Do not leave exposed
fluid unattended. Prevent children or pets from coming into
contact with the fluid. Clean up spills immediately.
Caution: Do not attempt any repairs on the CRT/optical block
assembly without first removing the CRT coupling fluid.
Removal of the delta output lens will result in spillage of the
coupling fluid.
B. Removing the PTV Coupling Fluid
All repairs made to the CRT/optical block assembly require the
removal of the coupling fluid. The following procedure
describes how to remove the PTV coupling fluid.
1. Lay the CRT assembly on its side with the plug pointing up.
2. Remove the plug (X8).
3. Remove some of the fluid from the coupler to prevent
spillage when the CRT is removed. An empty coupling fluid
bottle with a cone top is recommended to lower the fluid
level within the coupler. Squeeze and hold the bottle and
insert the tip of the cap into the drain hole of the coupler.
Loosen the grip on the bottle, allowing the fluid to be pulled
up into the bottle. Save the fluid.
4. Reinstall the plug (X8).
5. Stand the CRT assembly up with the neck of the CRT
pointing up.
6. With an awl or marking pen, outline the edges of the CRT
onto the coupler.
Note: The correct positioning of the CRT to the coupler is
critical to the optimum performance of the optical system.
7. Remove the four CRT mounting bolts (A) (with springs and
spacers) and remove the mounting bracket (D).
8. Remove the four CRT mounting ear screws.
Note: The CRT mounting ear screws are not used on some
assemblies.
9. Gently remove any metal shavings from around the screw
holes. Do not allow the metal shavings to get into the fluid.
Note the position of the high voltage anode cap with
respect to the coupler.
10. Carefully remove the CRT from the coupler. Wipe any
excess fluid from the faceplate of the CRT. Set the CRT
aside.
11. Use an empty coupling fluid bottle to extract the remainder
of the fluid from the coupler.
Note: Complete removal of the coupling fluid is not
necessary when only replacing the CRT.
12. Clean any remaining fluid from the coupler and the CRT
gasket channel using absorbent tissue. Refer to "C".
Cleaning the Coupler, C-element Lens, and CRT
Faceplate procedure if the fluid is discoloured or
contaminated.
13. Make all necessary repairs.
C. Cleaning the Coupler, C-Element Lens, and CRT
Faceplate
1. Remove CRT coupling fluid as described in steps B1
through B13.
2. Using denatured alcohol on a cloth made of 100% cotton
or a lens cleaning tissue, gently clean the C-element
(fisheye) lens, coupler and the CRT faceplate. Thoroughly
clean the coupler assembly, including the expansion
chamber bladder, and allow to fully dry.
Caution: Do not use soap or detergent type substances to
clean the coupler and its related assemblies. Water can be
used as an alternative to denatured alcohol, but the
assemblies must be completely dry before reassembly of
the coupler and the addition of the coupling fluid. A hair
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