TX-21AT1P - Panasonic TV Service Manual (repair manual). Page 2

SAFETY PRECAUTIONS ......................................................................................................................................................... 2 

SERVICE HINTS ...................................................................................................................................................................... 3 

ADJUSTMENT PROCEDURE AND SELF-CHECK .................................................................................................................. 4 

WAVEFORM PATTERN TABLE............................................................................................................................................... 5 

ALIGNMENT SETTINGS .......................................................................................................................................................... 6 

BLOCK DIAGRAMS.................................................................................................................................................................. 7 

PARTS LOCATION................................................................................................................................................................. 10 

REPLACEMENT PARTS LIST................................................................................................................................................ 11 

SCHEMATIC DIAGRAMS....................................................................................................................................................... 17 

CONDUCTOR VIEWS ............................................................................................................................................................ 20 

 

1.  It is advisable to insert an isolation transformer in the 

a.c. supply before servicing a hot chassis. 

2.  When servicing, observe the original lead dress in the 

high voltage circuits. If a short circuit is found, replace 
all parts that have been overheated or damaged by 
the short circuit. 

3.  After servicing, see that all the protective devices 

such as insulation barriers, insulation papers, shields 
and isolation R-C combinations are correctly 
installed. 

4.  When the receiver is not being used for a long period 

of time, unplug the power cord from the a.c. outlet. 

5.  Potentials as high as 28kV are 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 
familiar with the precautions necessary when working 
on high voltage equipment. Always discharge the 
anode of the tube. 

6.  After servicing make the following leakage current 

checks to prevent the customer from being exposed 
to shock hazard. 

1.  Unplug the a.c. cord and connect a jumper between 

the two prongs of the plug. 

2.  Turn on the receiver’s power switch. 
3.  Measure the resistance value with an ohmmeter, 

between the jumpered a.c. 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 4M ohm and 
20M ohm. When the exposed metal does not have a 
return path to the chassis, the reading must be 
infinite. 

1.  Plug the a.c. cord directly into the a.c. outlet. Do not 

use an isolation transformer for this check. 

2.  Connect a 2k

Ω 10W resistor in series with an 

exposed metallic part on the receiver and an earth, 
such as a water pipe. 

3.  Use an a.c. voltmeter with high impedance to 

measure the potential across the resistor. 

4.  Check each exposed metallic part and check the 

voltage at each point. 

5.  Reverse the a.c. plug at the outlet and repeat each of 

the previous measurements. 
 
 

6.  The potential at any point should not exceed  

1,4 Vrms. In case a measurement is outside the 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. 
 

(EARTH)

2kΩ 10 Watts

1.  The potential sources of X-Radiation in TV sets are 

the high voltage section and the picture tube. 

2.  When using a picture tube test jig for service, ensure 

that the jig is capable of handling 28kV without 
causing X-Radiation. 

: It is important to use an accurate periodically 

calibrated high voltage meter. 
1.  Set the brightness to minimum. 
2.  Measure the high voltage. The meter should indicate: 

  27kV ± 1kV. 
If the meter indication is out of tolerance, immediate 
service and correction is required to prevent the 
possibility of premature component failure. 

3.  To prevent any X-Radiation possibility, it is essential 

to use the specified tube.