Panasonic TX-21FX50T Service manual

Colour Television

TX-21FX50T

GP41 Chassis

ORDER NO. MTV0601002CE

Specifications

Power Source : AC SINGLE 220-240V, 50/60 Hz

Power Consumption : 67W

Aerial Impedance : 75Ω unbalanced

Coaxial type

Receiving System :

Receiving Channels :

VHF 2-12 PAL / SECAM B,K1

0-12 PAL B (N ZEALAND)

1-9 PAL B (N ZEALAND)

1-12 PAL / SECAM D

1-12 NTSC M (JAPAN)

2-13 NTSC M (U.S.A)

UHF 21-69 PAL G,H,I / SECAM G.K.KI

28-69 PAL B (Australia)

13-62 NTSC M (JAPAN)

14-69 NTSC M (U.S.A)

CATV S1-S20 (OSCAR)

1-125 (U.S.A CATV)

5A,9A (AUSTRALIA)

17 Systems

13-57 PAL D,K

C13-C49 (JAPAN)

21-237 (CHINA)

Audio Terminal : AV 1, 2, YUV, MONITOR OUT

RAV In Video In 1 Vp-p 75Ω

Audio In Approx. 400mVrms

Monitor Out Video Out 1 Vp-p 75Ω

Audio Out Approx. 400mVrms

High Voltage : 27.5kV ±1.5

at zero beam current

Picture Tube : A51LYZ295X

50.5cm (21 inches)

Measured diagonally,

90° deflection

Audio Output : 16.0W Dimensions : Height:472mm

Width : 648 mm Depth : 488 mm

Mass : 24 kg (Net Wt.)

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

TX-21FX50T

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. GP41 Chassis Block Diagram

2 Service Hints

2.1. Service Position for E-Board

2.2. Factory Mode Adjustment

2.3. Adjustment for White Balance

3 3 3 3 4

5 5 7

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

7 8 9

12 13

15 20

23 24

TX-21FX50T

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 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 connect 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 cabinet 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 MΩand 20 MΩ. When the exposed metal does not have a return path to the chassis, the reading must be infinite.

29.0kV

is present when this receiver is in operation. Operation of the receiver without the rear cover

1.3. Leakage Current Hot Check (Fig. 1)

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

2. Check a 2 kΩnon-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 handling

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 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.

29.0kV

without causing X-Radiation.

27.5±1.5kV

. If the meter indication is out of tolerance, immediate service

GP41 CHASSIS BLOCK DIAGRAM

TX-21FX50T

1.5. GP41 Chassis Block Diagram

SPEAKER

PVP

SCL

SDA

EEPROM

IC1101

IC1801

CVBS

R/G/B

V/L/R

AUDIO

AMP

IC2301

CVBS OUT

AUDIO

OUT

V_IN

MON_OUT

R/G/B

VCT-IF

IC601

TUNER

SCL SDA

R G B

V OUT H OUT

CRT

DRIVE

VM DRIVE

defl.

coil

CRT

MAIN

POWER

SWITCH

FRONT INPUTS

AV2 : V/L/R

GEOMAGNETIC

WOOFER

AMP

IC2401

REAR INPUTS

AV1 : V/L/R AV3 : YUV/V/L/R

FRONT INPUTS

AV2 : V/L/R

MON_OUT

29" models

PIP models

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.

TX-21FX50T

Fig. 2

2.2. Factory Mode Adjustment

1. Factory Mode Adjustment. a) Set timer ON b) Press remote’s RECALL (

2. To Set Self-Check: Press the volume down button on TV then press the Off Timer Button on remote control.

3. Service Mode 1 Controls

4. Service Mode 1 Function

) and panel’s volume down key simultaneously to enter SERVICE 1.

5. Service Mode 2 Controls To enter SERVICE 2; press channel key ‘1’ in SERVICE 1 entry screen.

TX-21FX50T

NOTE :- Service mode 2 options bit.

6. Service Mode 3 Controls To enter SERVICE 3; press channel key ‘1’ in SERVICE 2 entry screen.

7. Service Mode 3 Function

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 = 6.5 ± 1.0 nit.

2. Adjustment R-CUT OFF, so that X = 0.313 ± 0.015 nit.

3. Adjustment G-CUT OFF, so that Y = 0.320 ± 0.015 nit.

Adjustment of High Light

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

2. Adjustment R-Drive, so that X = 0.275 ± 0.015 nit.

3. Adjustment B-Drive, so that Y = 0.285 ± 0.015 nit.

TX-21FX50T

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.

TX-21FX50T

2.5. Adjustment Procedure

2.5.1. +B Voltage

Item / preparation

1. Operate the TV set.

2. Set control as follows :

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

Contrast ............... minimu m

Adjustment procedure

1. Confirm the DC voltage at the indicated test points, as follows : TPA 15 : 3.35 ± 0.2V TPA 16 : 141 ± 2V TPA 17 : 8.2 ± 0.5V TPA 18 : 1.9 ± 0.2V TPA 19 : 5.2 ± 0.2V TPA 20 : 175 ± 15V

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 16 and confirm the +B voltage is 141.0 ± 2V.

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

3. Normalize the brightness and contrast.

2.6. Adjustment

TX-21FX50T

Before Colour Purity, Convergence and White Balance adjustment are attempted,

V. Height, H. Centre and Focus adjustments must be completed.

Colour Purity

1. Set the Brightness and Contrast controls to their maximum positions.

2. Operate the TV set for 60 minutes.

3. Fully degausse the picture tube by using an external degaussing coil.

4. Apply a crosshatch pattern signal and adjust the static convergence magnets to the approximately correct position.

5. Receive a black and white signal.

6. Set the control as follows:

Red................minimum

Green.............minimum

Blue...............minimum

Press the Shipping button on the remote control twice to select CRT Adjustment Mode to select low light.

7. Loosen the clamp screw for the Deflection Yoke A in Fig. 10 and move the Deflection Yoke as close to the purity magnet as possible.

8. Adjust the purity magnetic rings so that a vertical green field is obtained at the centre of the screen.

Convergence

1. Apply a crosshatch pattern signal and Normalize Contrast control to the maximum positions.

2. Adjust Brightness until the grey position of the crosshatch pattern just becomes black.

3. Adjust the Red and Blue line at the centre of the screen by rotating the R-B static.

Fig. 6

9. Slowly push the Deflection Yoke and set it where a uniform green field is obtained.

Fig. 21

10. Re-adjust the Low Light controls to their correct settings and make sure that a uniform white field is obtained.

11. Tighten the clamp screw A in Fig. 10.

Fig. 8

4. Adjust Red and Blue with Green line at centre of the screen by rotating (RB)-G static convergence magnetic rings.

5. Lock convergence magnets with silicone sealer.

6. Remove the DY wedges and slightly tilt the Deflection Yoke vertically and horizontally to obtain the good overall convergence.

Fig. 9

7. Fix the Deflection Yoke byreinserting the DY wedges. Refer to Fig. 10.

8. If purity error is found, repeat “Colour Purity” adjustment.

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