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 symbol and 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.
An Isolation Transformer should always be used metallic part has a return path to the chassis, the
during the servicing of a receiver whose chassis is not reading should be between 240kΩ and 5.2MΩ. If the
isolated from AC power line. Use a transformer of exposed metallic part does not have a return path to
adequate power rating as this protects the technician the chassis, the reading should be infinite.
from accidents resulting in personal injury from
electrical shocks. It will also protect the Receiver from
being damaged by accidental shorting that may occur
When servicing, observe the original lead dress,
especially in the high voltage circuit. Replace all
damaged parts (also parts that show signs of
Always Replace Protective Devices, such as
fishpaper, isolation resistors and capacitors, and
shields after servicing the Receiver. Use only
manufacturer’s recommended rating for fuses, circuits
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
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
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
not nick or scratch the glass or subject it to any undue
pressure. When handling, use safety goggles and
heavy gloves for protection. 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
Avoid prolonged exposure at close range to unshielded
areas of the picture tube to prevent exposure to X-
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
Figure 1. Hot Check Circuit
WARNING: The potential source of X-ray radiation in the
TV set is in the High Voltage section and the picture tube.
Note: It is important to use an accurate, calibrated
high voltage meter.
to the restricting magnetic effects. When using a Set the brightness, picture, sharpness and color
picture tube test jig for service, ensure that the jig is
capable of handling 40kV without causing X-
controls to Minimum. Measure the High Voltage. The
high voltage should be 31.0 ± 1.0kV. If the upper limit is
out of tolerance, immediate service and correction is
Before returning a serviced receiver to the owner, required to insure safe operation and to prevent the
the service technician must thoroughly test the unit to possibility of premature component failure.
ensure that is completely safe to operate. Do not use a Horizontal Oscillator Disable Circuit Test
line isolation transformer when testing.
Leakage Current Cold Check
This test must be performed as a final check before the
Receiver is returned to the customer. See Horizontal
Unplug the AC cord and connect a jumper between the Oscillator Disable Circuit Procedure Check in
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