Tuner Unit Section - Sony XTL-W70 Service Manual

TUNER UNIT SECTION

• Use the following equipment for the electrical adjustment.
Equipment
1 Monitor TV (XVM-W71, 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
horizontal sync. signal
Color bar signal from TV signal generator
Connection points: See page 14.
Adjustment points: See page 14.
DC
power supply
POWER (CN4)
white (approx. 100%)
0.3 V
red
burst signal (flat)
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 45.75 MHz ± 1 kHz.
5. After this adjustment, open TP34. (Disconnect the spectrum
analyzer.)
45.75 MHz
AGC Adjustment
Procedure:
1. Set the TV SYSTEM switch to 1.
2. Input a color bar signal of 10ch (193.25 MHz) and 66 dBµV
(75 Ω OPEN).
3. Connect the digital voltmeter to TP42.
4. Adjust VR1 so that reading on the digital voltmeter is
3.0 ± 0.1 V.
AFT Adjustment
Procedure:
1. Input a color bar signal of 10ch (193.25 MHz) 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.
RGB Decoder FO Adjustment
Procedure:
1. Without INPUT1, INPUT2 inputs (no signal input mode), short
the jumper wire between TP100 and GND.
2. Connect a frequency counter to TP61.
3. Adjust VR6 so that reading on frequency counter is
3.579545 MHz ± 100 Hz.
4. After this adjustment, remove the jumper wires.
XTL-W70
2.5 Vp-p
0 V
13