Panasonic TC-21GX20P Schematic

Power

VHF

UHF

CATV

Audio

DVD

AV

Monitor

Colour Television

TC-21GX20P

GL1 Chassis

ORDER NO. MTV0701518CE

Specifications

Source : AC AUTO 110-240V, 50/60 Hz

Power Consumption : 58W

Aerial Impedance : 75Ω unbalanced

Coaxial type

Receiving System : 17 Systems

Receiving Channels :

2-13(U.S.A Standard)

14-69(U.S.A Standard)

1-125(U.S.A Standard)

Terminal :

Y 1.0 Vp-p, 75Ω

PB 0.7 Vp-p, 75Ω

PR 0.7 Vp-p, 75Ω

1, 2

Video In 1 Vp-p, 75Ω

Audio In Approx. 0.5V, 47kΩ

Out

Video Out 1 Vp-p, 75Ω

Audio Out Approx. 0.5V, 1kΩ

High Voltage : 27.5kV ±1.5

at zero beam current

Picture Tube : A51LYZ395X65

50.5cm (21 inches)

Measured diagonally,

90° deflection

Audio Output : 5W + 5w = 10W

Dimensions : Height : 472 mm

Width : 598 mm

Depth : 479 mm

Mass : 22.5 kg (Net Wt.)

Specifications are subject to change without notice.
Mass and dimensions shown are approximate.

© 2007 Matsushita Electric Industrial Co., Ltd. All
rights reserved. Unauthorized copying and
distribution is a violation of law.

TC-21GX20P

CONTENTS

Page Page

1 Safety Precautions 3

1.1. General Guide Lines

1.2. Leakage Current Cold Check

1.3. Leakage Current Hot Check (Fig. 1)

1.4. X-Radiation

1.5. GL1 Chassis Block Diagram

2 Service Hints

2.1. Service Position for E-Board

2.2. Factory Mode Adjustment

2.3. Adjustment for White Balance

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3

3

4

5

5

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2.4. Adjustment for CRT CUT OFF

2.5. Adjustment Procedure

2.6. Adjustment

3 Conductor Views

4 Schematic Diagram

4.1. A Board

4.2. L Board

5 Parts Locations

6 Replacement Parts List

6.1. Replacement Parts List

8

9

10

13

14

16

21

24

25

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TC-21GX20P

1 Safety Precautions

1.1. General Guide Lines

1. It is advisable to insert an isolation transformer in the AC supply before servicing this hot chassis.

2. When servicing, observe the original lead dress, especially the lead dress in the high voltage circuits. If a short circuit is found,
replace all parts which have been overheated or damaged by the short circuit.

3. After servicing, see to it that all the protective devices such as insulation barriers, insulation papers, shields and isolation R-C
combinations, are properly installed.

4. When the receiver is not to be used for a long period of time, unplug the power cord from the AC cord outlet.

5. Potential, as high as 29.0kV is present when this receiver is in operation. Operation of the receiver without the rear cover
involves the danger of a shock hazard from the receiver power supply. Servicing should not be attempted by anyone who is not
thoroughly familiar with the precautions necessary when working on high voltage equipment. Always discharge the anode of the
picture tube to the receiver chassis before handling the tube. After servicing make the following leakage current checks to
prevent the customer from being exposed to shock hazards.

1.2. Leakage Current Cold Check

1. Unplug the AC cord and connec t a jumper between the two prongs on the plug.

2. Turn on the receiver’s power switch.
Measure the resistance value, with an ohmmeter, between the jumper AC plug and each exposed metallic cabine t part on the
receiver, such as screw heads, aerials, connectors, control shafts, etc. When the exposed metallic part has a return path to the
chassis, the reading should be between 4 MΩ and 20 MΩ. When the exposed metal does not have a return path to the chassis,
the reading must be infinite.

1.3. Leakage Current Hot Check (Fig. 1)

1. Plug the AC cord directly into the AC outlet. Do not use an isolatio n transformer for this check.

2. Check a 2 kΩ non-inductive resistor and an AC/DC current meter, in series with each exposed metallic part on the receiver in
turn and an earth such as a water pipe.

The current from any point should not exceed 0.7 mA peak AC or 2 mA DC. In the case of a measurement being outside of
these limits specified, there is a possibility of a shock hazard and the receiver should be repaired and rechecked before it is
returned to the customer.

Fig. 1

1.4. X-Radiation

Warning:

The potential sources of X-Radiation in TV set are the EHT section and the picture tube. When using a picture tube test jig for
service, ensure that jig is capable of handlin g 29.0kV without causing X-Radiation.

Note: It is important to use an accurate periodically calibrated high voltage meter.

1. Set the brightness to minimum.

2. Use the remocon to get into Service Mode.

3. Measure the EHT. The meter reading should indicate 27.5±1.5kV. If the meter indication is out of tolerance, immediate service
and correction is required to prevent the possibility of premature component failure.

4. To prevent the possibility X-Radiation, it is essential to use the specified picture tube, if service replacement becomes
necessary.

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GL1 BLOCK DIAGRAM

Antenna

TUNER

SAW

Rear Inputs

AV 1 : V /L / R

Front Inputs

AV 2 : V / L/ R

YUV

YUV

CVBS4

CVBS2

IF

V

H

V OUT

H OUT

RGB

RGB

CRT

defl.

coil

MONITOR

OUT

SDA SCL

Audio Out

Mon Out

AUDIO

AMP

IC2302

IC601

UOC

EEPROM

IC1103

IC851

5V & 8V

IC801

T801

IC880

3.3V

PRIMARY

LIFE CCT

SPEAKER

TC-21GX20P

1.5. GL1 Chassis Block Diagram

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2 Service Hints

2.1. Service Position for E-Board

1. Remove the back cover.

2. Stand the TV set as shown in Fig. 2.

3. Remove the A-Board from the TV set by pulling the main board out as shown in Figure 2.

TC-21GX20P

Fig. 2

2.2. Factory Mode Adjustment

1. Adjustment.

a. Set Timer ON (30 minutes)

Press remote’s RECALL & panel’s vol down key simultaneously to select service mode.

b. CHK should appear on right side of TV screen.

After few second s CHK 1 should appear on right side of TV screen.

NOTE :

To move from CHK 1 to CHK 2 mode, etc, please follow below rotation:-

c. CHK 1

Press digit key “4” to move option mode forward.

Press digit key “3” to move option backward.

The function rotation will be as follows :-

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TC-21GX20P

d. After selecting the required option mode press Vol up / Vol down to adjust correct option. OSD will change to RED colour.

Press digit “0” to memorize data.

e. CHK2

Press digit key “2” to move forward to CHK2.

The function rotation will be as follows:-

f. Press digit key “4” to move forward from Colour ------> Sub-Colour, etc.

Press digit key “3” to move backward from Sub-Colour ------> Colour, etc.

g. Press volume up / volume down to adjust setting.

h. Press digit key “5” to make the AKB OFF (Blue OSD) - first time.

Press digit key “5” to make the AKB On (White OSD) - second time.

i. CHK3

Press digit key “2” to move forward to CHK 3.

The function rotation will be as follows:-

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j. Press digit key “4” to move forward from V-SLOPE ------> V-SHIFT

Press digit key “3” to move backward from V-SHIFT ------> V-SLOPE

k. Press volume up / volume down to adjust required setting.

l. CHK4

Press digit key “2” to move forward to CHK 4.

The function rotation will be as follows:-

TC-21GX20P

m. Press digit key “4” to move forward from R-CUT ------> G-CUT

Press digit key “3” to move backward from G-CUT ------> R-CUT

n. After selecting the required mode, press volume up / volume down to adjust required setting.

o. Press digit key “5” to make the AKB OFF and H-Line mode - first time.

Press digit key “5” to make the AKB ON and Normal picture - second time.

p. After finish adjustment, press Power ON / OFF button on remote control to go to normal TV mode.

2. HOW TO CHANGE CHANNEL BY I2C BUS CONTROLLER

a. Short FA1 and FA2

b. Select Slave address ‘70H’, Sub-address ‘43H’ for RF AGC.

*Example:

Slave Address = 70H’, Sub-Address = 43H’

Data = 80H’ = Center

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TC-21GX20P

2.3. Adjustment for White Balance

Preparation:

1. Receive the white balance pattern and aging should have been performed over 30 minutes.

2. Set the picture menu to DYNAMIC NORMAL.

3. Degausse the CRT face.

4. Fix the CRT colour analyzer receiver unit to CRT face.

Adjustment of Low Light.

1. Adjustment Sub Bright, so that Y = 6.3 ± 1.0 nit.

2. Adjustment R-CUT OFF, so that X = 0.233 ± 0.015 nit.

3. Adjustment G-CUT OFF, so that Y = 0.235 ± 0.015 nit.

Adjustment of High Light

1. Adjustment Sub Bright, so that Y = 150 nit.

2. Adjustment R-Drive, so that X = 0.262 ± 0.010 nit.

3. Adjustment G-Drive, so that Y = 0.264 ± 0.010 nit.

2.4. Adjustment for CRT CUT OFF

Preparation:

1. Connect the oscilloscope probe to TPL5.

2. Screen VR min.

3. Set the data Sub Bright, Bright.

4. In service Mode at “Bright” dac press [5] in factory mode to enter vertical line and adjust by volume down or up button.

5. Adjust “Screen VR” until 1-H Line appears.

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2.5. Adjustment Procedure

2.5.1. +B Voltage

Item / preparation

1. Operate the TV set.

2. Set control as follows :

Brightness ........... minimum

Contrast ............... minimum

Adjustment procedure

1. Confirm the DC voltage at the indicated test points, as follows :

TPA 10 : 141 ± 1.5V

TPA 12 : 3.3 ± 0.5V

TPA 09 : 5 ± 1V

2.5.2. High Voltage

Item / preparation

1. Receive the crosshatch pattern.

2. Set to 0 Beam.

Screen VR .......... minimum

Contrast .............. minimum

Adjustment procedure

1. Connect a DC voltage meter to TPA 10 and confirm the +B voltage is 141.0 ± 1.5V.

2. Connect a high frequency voltmeter to heater and confirm that voltage reads 6.3 ± 0.24 (VRMS).

3. Normalize the brightness and contrast.

TC-21GX20P

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