Sony WRR-855B, Service Manual, Page: 28 / 84

3-12
WRR-855B
8. Noise Squelch Adjustment
Equipment and Tools
• DC power supply: + 7.0
±
0.1 Vdc
• Signal generator
• DC voltmeter (digital multi meter)
• Audio analyzer
• Adjuster (0.4
x 1.3 mm) : 1 (Part No. 7-221-652-81)
• Power supply/AF OUT connector
(Refer to the ''How to make power supply/AF OUT
connector" on page 3-1.)
Connection
Same as ''5. FM Detector Adjustment".
Adjustment Location
RV205
CPU-342 board
ANT IN B ANT IN A
NOISE
DC voltmeter
+
_
Case
(3) Read the AF OUT level (Indicaton level of the Audio
analyzer ) . This level is specified to be 0 dB.
(4) Set the MODULATION of the signal generator to the
OFF (No modulation) .
(5) Check that the indication level of the audio analyzer is
_ 61 dB or less (S/N: 61 dB or more with A-weighted
filter) as compared with level of procedure (3) above.
(6) Change the RF OUTPUT (output level) of the signal
generator as shown below.
RF OUTPUT
: 10 dB
µ
V
EMF
( = _ 103 dBm)
(7) Check that indication level of the Audio analyzer
(level meter mode) is
_
38 dB or less (S/N: 38 dB or
more with A-weighted filter) as compared with level
of procedure (3) above.
(8) Change the RF OUTPUT and MODULATION of the
signal generator as shown below.
MODULATION : ON (modulation frequency=1 kHz).
RF OUTPUT
: 60 dB
µ
V
EMF
( = _ 53 dBm)
(9) Set the audio analyzer to the distortion meter mode.
(10)Check that the distortion ratio is
_
40 dB or less (1 %
or less with A-weighted filter).
ANT IN B side check
(11)Connect the signal generator to the ANT IN B connec-
tor.
(12)Perform the procedures (3) through (10) above for
ANT IN B side.
n
When checking the S/N at 10 dB
µ
V input, note the ANT
IN (A or B) connector which shows the better S/N. Use the
ANT IN (A or B) connector which shows the better S/N
for adjustment under ''8. Noise Squelch Adjustment".