Sony WRT-807B, Service Manual

Page: 23 / 64

3-7
WRT-807B (U/CE)
3-2-6. Distortion Ratio Check
Equipment and Tools
DC power supply
DC output voltage : + 1.5
±
0.1 Vdc
DC ammeter
Audio analyzer
Modulation analyzer
Oscilloscope
SMA-BNC (J) connector (Part No. J-6402-490-A)
RF conversion connector (Part No. J-6402-400-A)
AF input cable (See “ How to make a AF input cable” on
page 3-1.)
Connections
(For connecting the DC power supply, refer to the
“Preparation” on page 3-2.
Switch and Control Setting
Same as “Switch and Control Initial Setting” on page 3-3.
Procedure
(1) Connect the audio analyzer to the AF OUT connector
on the modulation analyzer.
(2) Connect the modulation analyzer to the antenna connec-
tor (CN305) with SMA-BNC (J) connector (and RF
conversion connector).
Set the modulation analyzer as below;
MEASUREMENT
: FM
MEASUREMENT RANGE : AUTO or
±
40 kHz
(manual operation)
HPF : 50 Hz
LPF : 15 kHz or 20 kHz
DE EMPHASIS : 50 u s
(3) Set the audio analyzer to distortion measurement
(distortion mode).
(4) Input 1 kHz,
_
55 dBV (
_
52.8 dBm) signal to the AF
input connector (CN303/CN-1868 board) with AF input
cable from audio analyzer (oscillator).
(5) Check that the distortion analyzer reading is less than
1.0 %.
(6) Input 1 kHz, _ 22 dBV ( _ 19.8 dBm) signal to the AF
input connector (CN303/CN-1868 board) with AF input
cable.
(7) Check that the distortion analyzer reading is less than 6
% (for CE57/CE62/CE67 model)/1.0 % (for U30/U42/
U62/U66 model).
Audio
analyzer
Oscilloscope
CN303
MB-860 board (B side)
CN305
Oscillator
Distortion meter
Level meter
Modulation
analyzer
AF input cable
RF IN
AF OUT
CN-1868 board
SMA-BNC (J) connector with
RF conversion connector