This supplement service manual is issued to add the modelss of the NA7DM family listed above to the main service
manual order No. MTNC010305C1 (CT-20D11E). Included in this supplement service manual are unique
characteristics and a complete parts list. Please file and use this simplified service manual together with main service
manual order No. MTNC010305C1
Chassis
“WARNING! This ServiceManualis designed forexperiencedrepairtechnicians only and is not designedfor use bythe general public.
It does not contain warnings or cautions to advise non-technical individuals of potential dangers in attempting to service a product.
Productspowered byelectricityshouldbeservicedorrepairedonlybyexperiencedprofessionaltechnicians.Anyattempttoservice
or repair the product or products dealt with in this Service Manual by anyone else could result in serious injury or death.”
The service technician is requiredtoreadand follow the “safety precautions”and“important safety notice” in this main manual.
Copyright2002by Matsushita Electric Corporation of
America. All rights reserved. Unauthorized copying
and distribution is a violation of law.
Important safety notice
Special components are used in this television set which are important for safety. These parts are identified on the
schematic diagram by the symboland printed in BOLD TYPE on the replacement part list. It is essential that
these critical parts are replaced with the manufacturer’s specified replacement part to prevent X-ray radiation,
shock, fire or other hazards. Do not modify the original design without the manufacturer’s permission.
Safety precautions
General guidelines
AnIsolationTransformershouldalwaysbe usedduring
the servicing of a receiver whose chassis is not
isolated from AC power line. Use a transformer of
adequate power rating as this protects the technician
from accidents resulting in personal injury from
electrical shocks. It will also protect the receiver from
being damaged by accidental shorting that may occur
during servicing.
When servicing, observe the original lead dress,
especially in the high voltage circuit. Replace all
damaged parts (also parts that show signs of
overheating.)
Alwaysreplaceprotectivedevices,suchas
fishpaper, isolation resistors and capacitors, and
shields afterservicing thereceiver.Useonly
manufacturer’s recommended rating for fuses, circuits
breakers, etc.
High potentials are present when this receiver is
operating. Operation of the receiver without the rear
cover introduces danger for electrical shock. Servicing
should not be performed by anyone who is not
thoroughly familiar with the necessary precautions
when servicing high-voltage equipment.
Extreme care should be practiced when handling the
picture tube. Rough handling may cause it to implode
due to atmospheric pressure. (14.7 lbs per sq. in.). Do
not nick or scratch the glass or subject it to any undue
pressure. When handling, use safety goggles and
heavygloves forprotection.Discharge the picture tube
by shorting the anode to chassis ground (not to the
cabinet or to other mounting hardware). When
discharging connect cold ground (i.e. dag ground lead)
to the anode with a well insulated wire or use a
grounding probe.
Avoid prolonged exposure at close range to unshielded
areas of the picture tube to prevent exposure to
X-ray radiation.
The test picture tube used for servicing the chassis at
the bench should incorporate safety glass and
magnetic shielding. The safety glass provide shielding
for the tube viewing area against X-ray radiation as
well as implosion. The magnetic shield limits the X-ray
radiation around the bell of the picture tube in addition
to the restricting magnetic effects. When using a
picture tube test jig for service, ensure that the jig is
capableofhandling35kVwithoutcausing
X-ray radiation.
Beforereturning a servicedreceiver totheowner,the
service technician must thoroughly test the unit to
ensure that is completely safe to operate. Do not use a
line isolation transformer when testing.
Leakage current cold check
Unplug the AC cord and connecta jumper between the
two plug prongs.
Measure the resistance between the jumpered AC plug
and expose metallic parts such as screwheads,
antenna terminals, control shafts, etc.
If the exposed metallic part has a return path to the
chassis, the reading should be between 240kΩ and
5.2MΩ. If the exposed metallic part does not have a
return path to the chassis, the reading should be
infinite.
Leakage current hot check (Fig. 1)
Plug the AC cord directly into the AC outlet. Do not use
an isolation transformer during the check.
Connect a 1.5kΩ 10 watt resistor in parallel with a
0.15µF capacitor between an exposed metallic part
and ground. Use earth ground, for example a
water pipe.
Using a DVM with a 1000 ohms/volt sensitivity or
higher, measure the AC potential across the resistor.
Repeat the procedure and measure the voltage
present with all other exposed metallic parts.
Verify that any potential does not exceed 0.75 volt
RMS. A leakage current tester (such a Simpson model
229, Sencore model PR57 or equivalent) may be used
in the above procedure, in which case any current
measure must not exceed 0.5 milliamp. If any
measurement is out of the specified limits, there is a
possibility of a shock hazard and the receiver must be
repaired and rechecked before it is returned to the
customer.
AC VOLTMETER
COLD
WATER
PIPE
(GROUND)
0.15µF
TO
INSTRUMENT’S
EXPOSED METAL
PARTS
1500Ω,10 W
Figure 1. Hot check circuit
X-ray radiation
WARNING: The potential source of X-ray radiation in the
TV set are the High Voltagesection and the picture tube.
Refer to X-RAY protecton circuit check in service
notes in this manual to confirm HHS voltage.
High voltage (crt anode)
Confirm Anode voltage is within limits:
Set the BRIGHTNESS, PICTURE, SHARPNESS and
COLOR to minimum (To obtaina dark image). Measure
high voltage. It should be:
26.60
± 1.25kV.
If the upper limit is out of tolerance, immediate service
and correction is required.
Note: It is important to use an accurate, calibrated
high voltage meter.
Note: These components are affixed with glue. Be careful not to break or damage any foil under the
component or at the pins of the ICs when removing. Usually applying heat to the component for a short time
while twisting with tweezers will break the component loose.
Leadless chip component
(surface mount)
Chip components must be replaced with identical chips
due to critical foil track spacing. There are no holes in
the board to mount standard transistors or diodes.
Some chips capacitor or resistor board solder pads
may have holes through the board, however the hole
diameter limits standard resistor replacement to 1/8
watt. Standard capacitor may also be limited for the
same reason. It is recommended that identical
components be used.
Chip resistor have a three digit numerical resistance
code - 1st and 2nd significant digits and a multiplier.
Example: 162 = 1600 or 1.6kΩ resistor, 0 = 0Ω (jumper).
Chip capacitors generally do not have the value
indicated on the capacitor. The color of the component
indicates the general range of the capacitance.
Chip transistors are identified by a two letter code. The
first letter indicates the type and the second letter, the
grade of transistor.
Chip diodes have a two letter identification code as per
the code chart and are a dual diode pack with either
common anode or common cathode. Check the parts
list for correct diode number.
Component removal
1. Use solder wick to remove solder from component
end caps or terminal.
2. Without pulling up, carefully twist the component
with tweezers to break the adhesive.
3. Donotreuseremovedleadlessorchip
components since they are subject to stress
fracture during removal.
Chip component Installation
1. Put a small amount of solder on the board
soldering pads.
2. Hold the chip component against the soldering
pads with tweezers or with a miniature alligator clip
and apply heat to the pad area with a 30 watt iron
until solder flows. Do not apply heat for more than
3 seconds.
TYPE
b
e
ANODES
MH DIODE
Chip components
GRADE
c
TRANSISTOR
COMMON
CATHODE
SOLDER
CAPS
CAPACITOR
1ST DIGIT
RESISTOR
SOLDER
CAPS
2ND DIGIT
MULTIPLIER
=1600 = 1.6k
How to replace Flat-IC
- Required tools -
•Soldering iron•De-solder braids
•Sharpen pliers (wire
cutters and long nose)
1. Cut the pins ofthe defective IC with the wire cutters
pliers, and remove it completely away from the
board. If the IC is glued to the board, apply hot air
to complete the removal. CAUTION- Do not pull or
twist the pliers, may damage the soldering pads in
the board.
Flat-IC
2. Using the soldering Iron and the long nose pliers,
remove the IC pins that still attached to the board.
3. Using the de-solder braid and the soldering iron,
remove the solder from the board soldering pads.
4. Position the new Flat-IC in place (apply the pins of
the Flat-IC to the soldering pads where the pins
need to be soldered). Properly determine the
positions of the soldering pads and pins by
correctly aligning the polarity symbol. Start aligning
and soldering pin no.1, then align and solder the
pin in the apposite corner of the IC, this will help to
align the rest of the pins.
Polarity
symbol
5. Solder all pins to the soldering pads using a fine
tipped soldering iron.
Solder
6. Check with a magnifier for solder bridge between
the pins or for dry joint between pins and soldering
pads. To remove a solder bridge, use a de-solder
braid as shown in the figure below.
Solder
bridge
-4-
•Magnifier
Soldering
iron
De-Solder
braid
Soldering
iron
Soldering
iron
De-Solder
braid
Soldering
iron
Service notes (continued)
IMPORTANT: To protect against possible damage to
the solid state devices due to arcing or static discharge,
make certain that all ground wires and CTR DAG wire
are securely connected.
CAUTION: The power supply circuit is above earth
ground and the chassis cannot be polarized. Use an
isolation transformer when servicing the receiver to
avoid damage to the test equipment or to the chassis.
Connect the test equipment to the proper ground ( ) or
() when servicing, or incorrect voltages will be
measured.
Procedure:
1. Connect receiver to isolator transformer.
2. Apply a monoscope pattern.
3. In service mode. (Refer to service mode section)
select register C0b.
4. Measure TP5 (TPs port close to tuner). Compare
the measure of TP5 and set the data for C0b
according the following table
TP5
MEASURE (V)
DATA TO
C0b (Hex)
WARNING: This receiver has been designed to meet
or exceed applicable safety and x-ray radiation
protection as specified by government agencies and
independent testing laboratories.
To maintain original product safety design standards
relative to x-ray radiation and shock and fire hazard,
parts indicated with the symbolon the schematic
must be replaced with identical parts. Order parts from
the manufacturer’s parts center using the parts
numbers shown in this service manual, or provide the
chassis number and the part reference number.
For optimum performance and reliability, all other parts
shouldbereplacedwithcomponentsof
identical specification.
X-ray protection circuit check
This test must be performed as final check before the
receiver is returned to the customer. If voltage is out of
tolerance, immediate service and correction is required
to insure safe operation and to prevent the possibility of
premature component failure.
Equipment needed to check the protection circuit:
1. Isolator transformer.
2. High voltage meter.
3. Short jumper.
4. Diode connection jumper.
Use similar diode than D823, refer to parts list for
part No., (diode should support at least 150V.)
0 ~ 0.9300
0.93 ~ 0.9701
0.97 ~ 1.0102
1.01 ~ 1.0503
1.05 ~ 1.0904
1.09 ~ 1.1305
1.13 ~ 1.1706
1.17 ~ 1.2107
5. Exit service mode and turn receiver OFF.
6. Connect a jumper from TPD16 to TPD17.
7. Connect the
diode jumper
, cathode to TPD14
(cold GND), anode to TPD15 (hot GND).
Note: Refer to Fig. 2 for test point location.
8. Apply 75V AC to the AC input of the Insulator
transformer.Turn receiver ON.
9. Set PICTURE and BRIGTHNESS to minimum.
10. Increase the AC voltage at the input of Insulator
transformer and confirm the HHS voltage is
32.0kV, at the point set starts to loose sync,
11. Reset picture controls to original levels.
12. Turn the set OFF, and remove all jumpers and
connections from chassis.
-5-
Receiver feature table
FEATURE\MODELCT-20G7DFCT-20D12DF
Chassis NoAP391BP391
FamilyNA7DM
Number of channels181
Menu languageEng/Span/Fr
Closed CaptionX
V-ChipX
75 Ω inputX
Remote Model numberEUR501450EUR51 1502
PicturetubetypePANABLACK
Picture tube SupplierSAMSUNG
Comb Filter2DIG
V/A normV
FM Radio----X
MTS/SAP/DBXX
Built-in audio power1.5Wx2 (10%)
Number of speakers2
AI SoundX
A/V in (rear/front)1(1/1)
Audio Out (F:FAO/V:VAO)---F,V
S-VHS In (rear/front)---1/0
EPJ/HPJ/MISCHPJ
Dimensionsmm
(WxDxH)in
Weight (kg/lbs)18/39.6
Anode voltage
Video input jack1Vp-p 75Ω, phono
Audio input jack500mV rms, 47KΩ
A-Board TNP2AH040DH*DK*
C-Board TNP2AA106AF*
515.7x490.5x461.7
20.30x19.31x18.17
± 1.25 kV
26.60
Table 1. Receiver features
*Note: When ordering a board, add and ” S” after the board suffix application.
Example, If order A-Board for CT-20G7DF, should be ordered as:
TNP2AH040
DHS.
Specifications are subject to change without notice or obligation.
Dimensions and weights are approximate.
-6-
Chasis service adjustment procedures
All service adjustments are factory preset and should not require adjustment unless controls and/or
associated components are replaced.
Note: Connect the (-) lead of the voltmeter to the appropriate ground. Use IC801’s heat sink when the HOT
ground symbol ( ) is used. Otherwise, use COLD ground () — tuner shield, IC451’s heat sink or FA2.
Figure 2. A-Board main
components
and test points
IC552
IC551
T
U
N
E
R
FA1
CLK
DATA
FA2
IC2302
IC2301
IC002
IC001
A11
TPE10
TPE11
IC050
COLD ()
IC003
C825
TPD17
TPD15
TPD16
HOT ( )
F801
IC801
TPD14
CRT
GND
TPD9
IC451
D561
TPD8
D554
SCREENFOCUS
COMPONENTS WITHIN DOT LINES ARE LOCATED AT THE OPOSITESIDE OF BOARD.
130.0V B+ voltage confirmation
1. Set the BRIGHT and the PICTURE to minimum by
using the PICTURE menu.
2. Connect the DVM between C825 (+ side) and cold
ground ().
3. Confirm that B+ voltage is 130.0V ± 2.5V.This
voltage supplies B+ to the horizontal output &
flyback circuits.
Source voltage chart
120V AC line input. Set the BRIGHT and the PICTURE
to minimum by using the PICTURE menu. Use cold
ground