Tuner Unit Section - Sony XTL-750W Service Manual

TUNER UNIT SECTION

• Use the following equipment for the electrical adjustment.
Equipment
1 Monitor TV (XVM-750W, etc.)
2 Spectrum analyzer
3 TV signal generator
4 Digital voltmeter
5 Oscilloscope
6 Audio analyzer
7 DC power supply
8 Frequency counter
Equipment Connections
Connect the test equipment as shown in the figure below (unless
otherwise instructed) and perform the adjustment.
ANT IN
TV SG
set
RF out
Setup during Adjustment
Use the video signal obtained from the TV signal generator as the
alignment signal, and check that this signal is within video output
signal standards.
0.7 V
0.3 V
red
horizontal sync. signal
Color bar signal from TV signal generator (US model)
white (approx. 100%)
0.7 V
0.3 V
red
horizontal sync. signal
Color bar signal from TV signal generator (Hong Kong model)
Connection points: See page 14.
Adjustment points: See page 14.
DC
power supply
POWER (CN4)
white (approx. 100%)
0.3 V
burst signal (flat)
0.3 V
burst signal (flat)
– 12 –
TRAP Adjustment (Hong Kong model)
Procedure:
1. With the Power off, input the output of TG to TP30 (with DC
cut by a capacitor (0.01 µF)).
2. Connect a spectrum analyzer to TP31 (with DC cut by a
capacitor (0.01 µF)).
3. Adjust T1 so that the waveform peak is 39.75 MHz ± 50 Hz.
4. Adjust T2 so that the waveform peak is 30.0 MHz ± 50 Hz.
5. After this adjustment, open TP30 and TP31. (Disconnect the
spectrum analyzer.)
T1= 39.75 MHz
T2= 30.0 MHz
VCO Adjustment
Procedure:
1. No connection to ANT IN. (no signal state)
2. Connect a resistor (10 kΩ) between TP33 and +9 V (TP35).
3. Connect a spectrum analyzer to TP34 (with DC cut by a
capacitor (0.01 µF)).
4. Adjust T3 so that the waveform peak is 38.0 MHz ± 1 kHz
(Hong Kong model) or 45.75 MHz ± 1 kHz (US model).
5. After this adjustment, open TP34. (Disconnect the spectrum
analyzer.)
38.0 MHz (Hong Kong model)
45.75 MHz (US model)
AGC Adjustment
Procedure:
1. Set the TV SYSTEM switch to 1.
2. Input a color bar signal of C9ch (192.25 MHz) (Hong Kong
model) or 10ch (193.25 MHz) (US model) and 66 dBµV
(75 Ω OPEN).
3. Connect the digital voltmeter to TP42.
4. Adjust VR1 so that reading on the digital voltmeter is
6.0 ± 0.1 V (Hong Kong model) or 3.0 ± 0.1 V (US model).
AFT Adjustment
Procedure:
1. Input a color bar signal of C9ch (192.25 MHz) (Hong Kong
model) or 10ch (193.25 MHz) (US model) and 74 dBµV
(75 Ω OPEN).
2. Connect the oscilloscope to TP102.
3. Adjust T3 untill the waveform on the oscilloscope is 2.5 Vp-p.
Note: Small peaks (dips) coming out from the top of the
waveform are unacceptable.
2.5 Vp-p
0 V