7
(2) Never short-circuit the "HOT" and "COLD" circuit to prevent the fuse or other components from burning.
(3) Never connect any measuring equipment such as oscilloscope to both the "HOT" and "COLD" circuit at the same
time to prevent the fuse from burning. Also, connect the ground of the measuring equipment to the ground of the
circuit being tested.
(4) Never fail to unplug the power cord of the receiver before taking out the chassis.
TEST EQUIPMENT :
EQUIPMENT
SPECIFICATION
High Impedance Voltmeter
Having an impedance of at least 100 Kohm.
Oscilloscope
Volt sensitivity over 10mV input impedance over 1
Mohm, below 10PF.
Sweep/Marker Generator
Output adjustable to at least 0.1 volts rms.
Colour Bar Generator
With functions: BAR/DOT/SQUARE/SYSTEM
SELECT/VIDEO OUTPUT TERMINAL/CROSS-
HATCH/S-VIDEO OUTPUT TERMINAL functions
and green or red purity signal.
Power Supply
Source such as a battery or a well regulated and
isolated DC bias supply. (Adjust 0-20V)
AC/DC Voltmeter
High sensitive (better use digital voltmeter)
Isolation Transformer
Voltage adjustable type having capacity of more
than 200 watts.
Probe
Low-capacitance / High impedance.
FM/AM Signal Generator
National ; MODEL : VP8177A
B+ VOLTAGE ADJUSTMENT
Notice: (A) B+ voltage closely relates to the picture tube's positive high voltage.
(B) To prevent it from producing excessive hazardous X- RAY RADIATION, ensure that B+ voltage must be
adjusted to at the 108V POSITIONS.
1.
Check the AC line voltage suppl ied is -5% 50 Hz.
2.
Turn in an active channel, adjust BRIGHTNESS and CONTRAST controls to obtain a normal picture.
3.
Connect test point (C506) on the MAIN CHASSIS PCB with high impedance DC voltmeter.
4.
Adjust VR501 (on the MAIN PCB) for B+ 108V +/-0.3V voltage reading.
VCO IF ADJUSTMENT:
(1) In AV mode, disconnect the solder link( P1 ) on main chassis board.
(2) Connect an Oscilloscope Measure pin 1 of IC201.
(3) Does not apply signal to Tuner & Power on TV.
(4) Access service mode, then selects PIF VCO item adiustment setting date = 80
(5) Adjust the VCO coil (L204) so that the pin 1 of IC201 voltage is DC 2.5V and the waveform
(see Fig. 6)
(6) Press Factory handset [PP] key to finish.
(7) Turn off TV set and connect the solder link( P1 ) on main chassis board.
(1) Press Factory handset [ PP] key to finish.
5V 5V
2.5V 2.5V
