Hitachi 32UX01S, Service Manual

Page: 23 / 92

23
4-3 MTS ADJUSTMENT
4-3-1 Input Level Adjustment
Adjustment Preparation
(1) Apply a signal to output terminals of the Main
Tuner on the Main PWB using the circuit shown
below. Connect 100
Ω
resistor between AGC ter-
minal, Pin
햲
and GND.
Video signal
Generator
MTS signal
Generator
EXT
SYNC
IN
AUDIO
VIDEO
IF modulator
(50
Ω
output)
fp=45.75MHz
fs=41.25MHz
2200PF
50
Ω
11
IF modulator output signal waveform
(Color bar or all white)
Note : Video signal and Audio Signal
should be synchronized.
MAIN
TUNER
U101
1
IF
terminal
87.5%
25%
100%
Carrier 0
100
Ω
IF modulator output level and P/S
P=105dBu (50
Ω
termination)
S level; -3dB to P level
At this time, S/N ratio of F/E
video output is 45dB or less.
Sound modulation condition:
Noise reduction encoder: ON
Stereo signal;
햲
R=0 (L only), 300Hz, 30% modulation
햳
R=0 (L only), 3kHz, 30% modulation
Monaural signal;
햴
Monaural, 400Hz, 100% modulation
(PRE-EN Off)
SAP signal;
햵
SAP, 300Hz, 30% modulation (see note)
(2) Connect AC voltmeter Vo to I401 pin .
Use the AC voltmeter of Matsushita model
VP-950C or equivalent.
Adjustment Procedure
(1) Select sound input
햴
then adjust the data “A04”
to Vo= 500mVrmsw10mVrms at I401 pin .
4-3-2 Stereo VCO adjustment
Adjustment Preparation
(1) Same as items 4-3-1(1) and 4-3-1(2).
(2) Connect a frequency counter to I401 pin
. Use
1:1 Probe.
(Probe standard Ri
≥
1M
Ω
, Ci
≤
15pF)
(3) Should be no signal at pin
햸
(I401).
(4) Connect capacitor (100µF/16v) as it is shown.
(5) Select adjustment code “A01.”
Adjustment Procedure
(1) Adjust the data “A01” to set 15.73±0.1KHz by
왗
,
왘
keys.
(2) Remove capacitor (100µF/16v)
U101
R107
100
애
F/16v
R401
R402
C406
I401
14
7
+
-
+
-
40
40
40