Furuno CH-270, Service Manual

Page: 26 / 88

23
SG
75
Matching Transformer
02S1138-1
CN5
J6
1
2
TRX Board 06P0241
RX Amplifier
TP3
Figure 3.4
Procedures
To adjust receiver gain;
1. Set the frequency of the SG to 180 kHz.
2. Rotate R38 three steps from fully CCN position.
Figure 3.5
3. Unplug J6 and set the output level of the SG to 46 dBuV ( measured by the Volt-meter ).
4. Connect J6 and turn on CH-270.
5. Set the range to 1600 m, Gain to "10", and TVG to "0".
6. Adjust R57 to obtain 4.0
±
0.5 V at TP3 on TRX board.
7. Adjust transformers T1/T2/T3 so that the signal level at TP3 becomes maximum.
8. Readjust R57 to obtain 4.0
±
0.5 V at TP3.
9. Unplug J6 and set the output level of the SG to 53 dBuV. (measured by the Volt-meter)
10. Connect J6 and confirm that the signal level at TP3 is 9 VDC.
11. Unplug J6 and set the output level of the SG to 116 dBuV. (measured by the Volt-meter)
12. Set Gain to "0" and TVG to "10".
13. Adjust R70 so that the lowest level of the TVG curve at TP3 becomes 0.4
±
0.05 V.