CONTENTS
SAFETY PRECAUTIONS..........................................................................................................................................................2
SERVICE HINTS.......................................................................................................................................................................3
SERVICE POSITION.................................................................................................................................................................4
ADJUSTMENT PROCEDURE...................................................................................................................................................5
ADJUSTMENT PROCEDURE AND SELF-CHECK ..................................................................................................................6
WAVEFORM PATTERN TABLE ...............................................................................................................................................7
ALIGNMENTSETTINGS...........................................................................................................................................................8
BLOCK DIAGRAMS..................................................................................................................................................................9
PARTSLOCATION.................................................................................................................................................................13
REPLACEMENTPARTS LIST................................................................................................................................................14
SCHEMATIC DIAGRAMS.......................................................................................................................................................23
CONDUCTOR VIEWS.............................................................................................................................................................28
SAFETY PRECAUTIONS
GENERAL GUIDE LINES
1. It is advisable to insert anisolation transformer in the
AC 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
suchasinsulationbarriers, 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 AC outlet.
5. Potentials ashigh as29,5kV {29,2kV} [29kV]are
present when this receiver is in operation. Operation
of the receiver without the rear cover involves the
danger of a shock hazard fromthe receiver power
supply. Servicing should not be attempted by anyone
who is not familiar with the precautionsnecessary
when working on high voltage equipment. Always
dischargethe anode of the tube.
6. After servicing make the following leakage current
checks to prevent the customer frombeing exposed
to shock hazard.
LEAKAGE CURRENT COLD CHECK
1. Unplug the AC cord and connect a jumper between
the two prongs ofthe plug.
2. Turn on the receiver’spower switch.
3. Measure the resistance value with anohmmeter,
between the jumperedAC plug and each exposed
metallic cabinet part onthe receiver, such asscrew
heads, aerials, connectors, control shaftsetc. When
the exposed metallic part has a return path to the
chassis, the reading should bebetween 4M ohm and
20M ohm. When the exposed metal does not have a
return path to the chassis, the reading must be
infinite.
LEAKAGE CURRENT HOT CHECK
1. Plug the AC cord directly into the AC outlet. Do not
use an isolation transformer for this check.
2. Connect a 2kΩ10W resistor in series with an
exposed metallic part on the receiver and an earth,
suchasa water pipe.
3. Use an AC voltmeter with high impedance to
measure the potentialacrossthe resistor.
4. Check each exposed metallic part and check the
voltage at each point.
5. Reverse the AC plug atthe outlet and repeat each of
the above measurements.
6. The potential at any point should not exceed
1.4 Vrms. Incase a measurement is outsidethe 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.
X-RADIATION WARNING
1. The potential sources of X-Radiation inTVsets are
the high voltage section and the picture tube.
2. When using a picture tubetest jig for service, ensure
that the jig is capable of handling 29,5kV without
causing X-Radiation.
NOTE: It is important to use an accurateperiodically
calibratedhigh voltage meter.
1. Set the brightness to minimum.
2. Measure the high voltage. The meter should indicate.
TX-28MD4 28,5kV ± 1kV.
TX-25MD4 28,2kV ± 1kV.
TX-21MD4 28kV ±1kV.
If the meter indication isout of tolerance, immediate
service and correction is required to prevent the
possibility of premature component failure.
3. To prevent any X-Radiation possibility, it isessential
to use the specified tube.
HOT CHECK CIRCUIT
A.C. VOLTMETER
WATER PIPE
(EARTH)
TO INSTRUMENT’S EXPOSED
METALLIC PARTS Fig. 1.
2kΩ10 Watts
2
