Quasar SP-2725F, Service Manual

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IMPORTANT: To protect against possible damage to
the solid state devices due to arcing or static discharge,
make certain that all ground wires and CRT DAG wire
are securely connected.
CAUTION: The power supply circuit is above earth
ground and the chassis cannot be polarized. Use an
isolation transformer when servicing the receiver to
avoid damage to the test equipment or to the chassis.
Connect the test equipment to the proper ground ( ) or
(
) when servicing, or incorrect voltages will be
measured.
WARNING: This receiver has been designed to meet
or exceed applicable safety and x-ray radiation
protection as specified by government agencies and
independent testing laboratories.
To maintain original product safety design standards
relative to x-ray radiation and shock and fire hazard,
parts indicated with the symbol on the schematic
must be replaced with identical parts. Order parts from
the manufacturer’s parts center using the parts
numbers shown in this service manual, or provide the
chassis number and the part reference number.
For optimum performance and reliability, all other parts
should be replaced with components of identical
specification.
X-ray Protection Circuit Check &
Adjustments
This test must be performed as final check before the
receiver is returned to the customer. If voltages are out
of tolerance, immediate service and correction is
required to insure safe operation and to prevent the
possibility of premature component failure.
Equipment:
1.
Isolation transformer.
2. High voltage meter.
3. Short jumper.
4. Jumper diode (same as D823, PN S3L60P154004).
diode should be rated a minimum of 150V.
Procedure:
1.
Connect the receiver to an isolation transformer.
turn receiver ON.
2. Apply a monoscope pattern.
3. In service mode (see service mode section in this
manual) select register C0B.
4. Measure TP5 (located near the tuner). Compare
the measured value to the left column of the table
below. Set C0B with value from the right column
corresponding to the measured level at TP5.
Example, if the measured level at TP5 is 1.03V, set
C0B to 03.
5. Exit service mode and shut the TV OFF.
6. Connect the short jumper between TPD16 and
TPD17.
7. Connect the jumper diode between TPD14 and
TPD15 (cathode connected to TPD14, anode
connected to TPD15).
8. Apply 75VAC to the input of the isolation
transformer.
9. Turn receiver ON.
10. Set PICTURE and BRIGHTNESS to minimum.
11. Slowly increase the voltage at the input of the
isolation transformer and confirm HHS voltage
measure 35.0KV when the receiver starts to go out
of sync.
12. Turn receiver OFF and remove jumper & diode.
TP5 MEASUREMENT SET C0B TO (HEX)
0 ~ 0.93V 00
0.93 ~ 0.97V 01
0.97 ~ 1.01V 02
1.01 ~ 1.05V 03
1.05 ~ 1.09V 04
1.09 ~ 1.13V 05
1.13 ~ 1.17V 06
1.17 ~ 1.21V 07