1. SAFETY INSTRUCTIONS .
GENERAL GUIDELINES the receiver, such as screw heads, aerials,
1. It is advised to insert an isolation transformer connectors, control shafts etc. When the
in the AC supply before servicing a hot exposed metallic part a return path to the
chassis. chassis the reading should be between
4Mohm and the 20Mohm. When the exposed
2. Potentials as high as 33KV are present when metal does not have a return path to the
this receiver is in operation. Operation of the chassis, the reading must be infinite.
receiver without the rear cover involves the
danger of a shock hazard from the receiver LEAKAGE CURRENT HOT CHECK
power supply. Servicing should not be 1. Plug the AC cord directly in to the AC outlet.
attempted by any one who is not competent Do not use an isolation transformer for this
with the precautions necessary when working check.
on the high voltage equipment. Always 2. Connect a 2Kohm 10W resistor in series with
discharge the anode of the tube. an exposed metallic part on the receiver and
an earth, such as a water pipe.
3. When servicing observe the original lead 3. Use an AC voltmeter with high impedance to
dress in the high voltage circuits. If a short measure the potential across the resistor.
circuit is found, replace all the parts which 4. Check each exposed metallic part and
have been overheated or damaged by the check the voltage at the each point.
short circuit. 5. Reverse the AC plug at the outlet and repeat
each of the above measurements.
4. Always use the manufacturer?s replacement 6. The potential at the any point should not
safety components. The critical safety exceed 1.4 Vrms. In case a measurement is
components marked with on the outside the limits specified, there is the
schematics diagrams should not be replaced possibility of a shock hazard, and the receiver
by other substitutes. Other substitute may should be repaired and rechecked before it
create the electrical shock, fire or other is returned to the customer.
hazards. Take attention to replace the
spacers with the originals. Furthermore where
a short circuit has occurred, replace those
components that indicate evidence of HOT CHECK CIRCUIT
overheating. AC-Voltmeter
TO INSTRUMENTS
5. After servicing, see that all the protective EXPOSED
devices such as insulation barriers, insulation METALLIC PARTSWater pipe
(earth)
papers, shields and isolation R-C
combinations are correctly installed.
2 K Ohm
6. When the receiver is not being used for a
long time of period of time, unplug the
power cord from the AC outlet.
Figure 1
7. After servicing make the following leakage X-RAY RADIATION WARNING
current checks to prevent the customer from
The primary source of X-ray radiation in this receiver
being exposed to shock hazard. is the picture tube. The chassis is specially
LEAKAGE CURRENT COLD CHECK
1. Unplug the AC cord and connect a jumper constructed to limit X-ray radiation. For continued X-
ray radiation protection, replace the tube with the
between the two prongs of the plug.
same type of the original one.
2. Turn the receiver?s power switch on. CAUTION
3. Measure the resistance value with an AFTER REMOVAL OF THE ANODE CAP, DISCHARGE THE
ANODE OF THE PICTURE TUBE AND THE ANODE CAP TO
ohmmeter, between the jumpered AC plug
and each exposed metallic cabinet part on THE METAL CHASSIS, CRT SHIELD, OR THE CARBON
PAINTED ON THE CRT WITH A HIGH VOLTAGE PROBE
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ACEC
