Sony WRT-822B, Service Manual

Page: 20 / 46

3-12
WRT-822B
MB-940 Board
(A side)
Spectrum analyzer
CN301
TP501 (GND)
Connect a jumper wire between
TP200 and TP501 (GND) by soldering.
(TONE signal : OFF).
TP200
MM-SMA (J)connector with SMA-BNC (J) connector
Jumper
wire
Procedure
n
Perform the checking with the MIC input connector short-
circuited.
(1) Set the spectrum analyzer as follow:
CENTER FREQUENCY (fc):
CE21 model; 470.125 MHz
CE33 model; 566.125 MHz
CE62 model; 798.125 MHz
CE67 model; 838.125 MHz
U14 model; 470.125 MHz
U30 model; 566.125 MHz
U62 model; 758.125 MHz
U66 model; 782.125 MHz
REFERENCE LEVEL: 20 dBm
FREQUENCY SPAN: 200 kHz (20 kHz/DIV)
RBW (resolution band width): 3 kHz
VBW (video band width):
1 kHz
ATT: 30 dB
(2) Decrease gradually the DC output voltage of the DC
regulated power supply and confirm that the battery
alarm signal turns on at 2
±
0.2 V.
(3) Check that level difference between carrier frequency
(center frequency level) on spectrum analyzer and tone
signal is with in 29
±
2 dB.
V : 10 dB/div
H : 20kHz/div
29
±
2 dB
20 dBm
fc
32.782 kHz
2. Frequency check
Connections
(For connecting the DC power supply, refer to the “Preparations”
on page 3-2.)
Procedure
n
Perform the checking with the Mic input connector (SMC9-
4P) short-circuited.
(1) Set the modulation analyzer as follows:
MEASUREMENT: FM
MEASUREMENT RANGE:
±
40 kHz
HPF: 4 kHz
LPF: >20 kHz
DE EMPHASIS: OFF
(2) Set the DC output voltage of DC power supply to 1
±
0.1
V so that battery alarm signal goes on.
(3) Check that frequency counter (resolution:0.1 Hz) read-
ing is 32.782 kHz
±
1 Hz.
(4) After the checking, remove (unsolder) the jumper wire
between TP200 and TP501 (GND) on the MB-940
board (A-side).