Service Notes
IMPORTANT: To protect against possible damagEquie tpmeont needed to check the disabled circuit:
the solid state devices due to arcing or static
1. Voltmeter (0 - 200V scale)
discharge, make certain that all ground wires and CRT
DAG wire are securely connected.2. High Voltage Meter (0- 50kV)
CAUTION: The power supply circuit is abov3. Ve eaarrtihac or Isolation Transformer
ground and the chassis cannot be polarized. Use an
Procedure:
isolation transformer when servicing the Receiver to
1. Tune in a station to verify that the horizontal is
avoid damage to the test equipment or to the chassis.
in sync.
Connect the test equipment to the proper ground ( ) or
( ) when servicing, or incorrect voltage2.s wObitlali bn a Moenoscope pattern or a signal generator
measured.crosshatch pattern
WARNING: This Receiver has been designed to3. meeTutrn the Receiver OFF. Connect a jumper across
or exceed applicable safety and X-ray radIC80iatio3 npin 3 and pin 4. Apply +9V DC to cathode of
protection as specified by government agencieD00s an1.d
independent testing laboratories.
4. Reduce the AC supply voltage to approximately
To maintain original product safety design st45Vandar. Codsnnect the high voltage meter to the CRT
relative to X-ray radiation and shock and firanoe hade.za (rdH,.V. button).
Note: Use the Dag Ground (C10 on the CRT Board)
parts indicated with the s! y onmbol the schematic
to connect the (-) lead of the meter.
must be replaced with identical parts. Order parts from
5.Turn the Receiver ON. Slowly increase the AC
the manufacturer?s parts center using the parts
supply voltage and verify that the high voltages
numbers shown in this service manual, or provide the
does not exceed37. 1kV, when horizontal just
chassis number and the part reference number.
begins to pull out of sync. If the high voltage is not
For optimum performance and reliability, all othwiterh pina therts specified limit, the cause must be
should be replaced with components of
determined and corrected before the Receiver is
identical specification.
returned to the customer.
Horizontal Oscillator Disable Circuit
This chassis employs a special circuit to protect
against excessive high voltage and beam current. If, for
any reason, the high voltage and beam current exceed
a predetermined level this protective circuit activates
and detunes the horizontal oscillator that limits the high
voltage. The over-voltage protection circuit is not
adjustable. However, if components indicated by the
symbol ! on the schematic in either the horizontal
sweep system or the over-voltage protection circuit
itself are changed, the operation of the circuit should
be checked using the following procedure:
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