27R-S200, 27R-S400
27R-S450, CR27S20
CSR20027
IMPORTANT SERVICE SAFETY PRECAUTION
�Service work should be performed only by qualified service technicians who are
thoroughly familiar with all safety checks and the servicing guidelines which follow:
WARNINGX-RADIATION AND HIGH VOLTAGE LIMITS
1. For continued safety, no modification of an1.y circuitBe sure all service personnel are aware of the
should be attempted.procedures and instructions covering X-radiation. The
2. Disconnect AC power before servicing.only potential source of X-ray in current solid state
3. Semiconductor heat sinks are potential shockTV receivers is the picture tube. However, the picture
hazards when the chassis is operating.tube does not emit measurable X-Ray radiation, if
4. The chassis in this receiver has two ground systemsthe high voltage is as specified in the "High Voltage
which are separated by insulating material. The non-Check" instructions.
isolated (hot) ground system is for the B+ voltageIt is only when high voltage is excessive that X-
regulator circuit. The isolated ground system is fradiation is capaborle of penetrating the shell of the
the low B+ DC voltages and the secondary circuit ofpicture tube including the lead in the glass material.
the high voltage transformer.The important precaution is to keep the high voltage
To prevent electrical shock use an isolationbelow the maximum level specified.
transformer between the line cord and power2. It is essential that servicemen have available at all
receptacle, when servicing this chassis.times an accurate high voltage meter.
The calibration of this meter should be checked
periodically.
CAUTION : FOR CONTINUED3. High voltage should always be kept at the rated value
PROTECTION AGAINST A-no higher. Operation at higher voltages may cause
RISK OF FIRE, REPLACEa failure of the picture tube or high voltage circuitry
4A 125VONLY WITH SAME TYPE 4A-and;also, under certain conditions, may produce
125V FUSE.radiation in exceeding of desirable levels.
4. When the high voltage regulator is operating properly
SERVICING OF HIGH VOLTAGE SYSTEMthere is no possibility of an X-radiation problem. Every
time a color chassis is serviced, the brightness shouldAND PICTURE TUBE
be tested while monitoring the high voltage with a
When servicing the high voltage system,meter to be certain that the high voltage does not
remove the static charge by connecting aexceed the specified value and that it is regulating
correctly.
10k ohm resistor in series with an insulated
5. Do not use a picture tube other than that specified or
wire (such as a test probe) between the pic-
make unrecommended circuit modifications to the
high voltage circuitry.ture tube ground and the anode lead. (AC
line cord should be disconnected from A6.CWhen trouble shooting and taking test measurements
outlet.)on a receiver with excessive high voltage, avoid being
unnecessarily close to the receiver.
Do not operate the receiver longer than is necessary1. Picture tube in this receiver employs integral implosion
protection.
to locate the cause of excessive voltage.
2. Replace with tube of the same type number for
continued safety.
3. Do not lift picture tube by the neck.
4. Handle the picture tube only when wearing
shatterproof goggles and after discharging the high
voltage anode completely.
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ACEC
SHARP
