Adjustment Procedures; Audio Circuit - Mitsubishi Electric WT-46807 Service Manual

MODELS: WT-46807 / WS-55807 / WS-55857 / WS-55907 /WS-65807 / WS-65857 / WS-65907 / WS-73907

[Audio Circuit]

1. MCS Input Level
Measuring
Oscilloscope
Instrument
Test Point
Connector JA pins 6 & 8
------
Ext. Trigger
Measuring
50mV/Div
Range
RF Stereo
Input Signal
300 Hz modulation
RF Input
Input Terminal
[Audio Circuit]
2. Separation
Measuring
Oscilloscope
Instrument
Test Point Conector JA pin 8
------
Ext. Trigger
Measuring
10mV/Div
Range
RF Stereo
Input Signal
RF Input
Input Terminal
Purpose:
Check the input signal level to the MCS circuit
Symptom:
Distorted sound during a stereo broadcast.
1. Supply an RF MCS signal to the Ant A input, 300 Hz at 100% modulation
(25 kHz deviation) for right and left channels.
2. Connect the oscilloscope to connector JA pin 8 (Main Tuner Right Audio).
3. Enter the Adjustment Mode and select the Audio Function.
4. Verify that the Audio Function items are set to the data values given the
table below.
5. Set the data for Item "1 INP" for 1.56 Vp-p ±0.06V.
6. Connect the oscilloscope to connector JA pin 6 (Main Tuner Left Audio).
7. Confirm that the left audio level at pin 6 of the JA connector is 1.56 Vp-p
±0.06V.
Note: Adjustment 2 (Stereo Separation) must be performed after this adjustment)
CIRCUIT ADJUST MODE
Activate ........ MENU-8-2-5-7
Function .................AUDIO
Item No. .................VIDEO
Adjust Data ...........ADJUST
Save Data .... .........ENTER
Exit ..............MENU (twice)
Purpose
Check stereo separation
Poor stereo separation
Symptom:
Note: This adjustment must follow Adjustment 1 (Input Level)
1. Supply a RF Stereo Signal (dual tone stereo) to the Ant. A input.
• Left Channel = 300 Hz modulation
• Right Channel = no modulation
2. Connect the oscilloscope to connector JA pin 8 (Main Tuner Right Audio).
3. Enter the Adjustment Mode and select the Audio Function.
4. Set the data for Item "3 WDE" for minimum Right Audio signal.
5. Change the modulation frequency to 3kHz.
6. Adjust the data for Item "4 SPC" for minimum Right Audio signal.
CIRCUIT ADJUST MODE
Activate ........ MENU-8-2-5-7
Function .................AUDIO
Item No. .................VIDEO
Adjust Data ...........ADJUST
Save Data .... .........ENTER
Exit ..............MENU (twice)
Page 32
AUDIO Function
Item # Abbrev.
1 INP
3 WDE
4 SPC
Data
7
16
16