Sharp 25MR15J, Service Manual

Page: 9 / 26

9
25MR15J
SERVICE INSTRUCTIONS
Ë
MTS ADJUSTMENT
MTS LEVEL ADJUSTMENT
1. Feed the following monaural signal to pin (14) of
IC3001.
Monaural signal: 400Hz, 245mVrms
2. Connect the rms voltmeter to pin (39) of IC3001.
3. Enter the service mode and select the service
adjustment "M01".
4. Adjust the data so that the rms voltmeter reads
490
±
10mVrms.
MTS VCO ADJUSTMENT
1. Keep the unit in no-signal state.
2. Connect the frequency counter to pin (39) of IC3001.
3. Connect a capacitor (100
µ
F, 16V) in between
po) side of C3005 and ground.
4. Enter the service mode and select the service
adjustment "M02"
5. Adjust the data so that the frequency counter reads
62.94
±
0.75kHz.
FILTER ADJUSTMENT
1. Feed the following stereo pilot signal to pin (14) of
IC3001 .
Stereo pilot signal: 9.4kHz, 600mVrms.
2. Enter the service mode and select the service
adjustment "M03".
3. Adjust the data at the point where "OK" appears on
the screen. The "OK" represents the approximate
center of the adjustable range of the data.
SEPARATION ADJUSTMENT
1. Connect the rms voltmeter to pin (39) of IC3001.
2. Receive the following composite stereo signal 1.
Composite stereo signal: 30% modulation, left
channel only, noise reduction on, 300Hz
3. Enter the service mode and select the service
adjustment "M04".
4. Adjust the data until the AC voltage reading of the
rms voltmeter is minimum.
5. Receive the following composite stereo signal 2.
Stereo signal: 30% modulation, left channel only,
noise reduction on, 3kHz
6. Enter the service mode and select the service
adjustment "M05".
7. Adjust the data until the AC voltage reading of the
rms voltmeter is minimum.
8. Take the above steps 1 thru 7 again for fine
adjustment.