3) Observe the waveform on the spectrum analyzer and turn RV21 to adjust the modulation degree of a sub spectrum �A� in the figure 4 to be narrowest as shown below.
4) At this time, measure AC voltage of IC21 Pin 1 on the TX board with AC voltmeter and define the value as �V0� for the next adjustment. 5) Turn the RV21 again so that the AC voltage of IC21 Pin 1 becomes the same value as the two thirds of �V0�. (V1=V0 � 2/3) Adjustment Location: TX board (See page 6.) Adjustment and confirmation without a spectrum analyzer Please confirm the units by following procedure shown below. Here a series of procedure which can be performed without a spectrum analyzer is introduced. Deviation adjustment/confirmation 1) Input a 400 Hz 316 mV signal into the left channel of transmitter. 2) Measure the AC voltage at the Pin 1 of IC21 (MJM2100M) with AC voltmeter. Spec.: 100 ± 10 mVrms If not, turn RV21 for obtaining the value. Adjustment Location: TX board (See page 6.) Sub-carrier frequency and output level confirmation 1) No signal is input into transmitter. 2) Connect a oscilloscope and a frequency counter to the test point TP1. 3) Confirm the voltage is within the following spec. Spec.: 0.55 Vp-p
0.55 Vp-p
4) Confirm the frequency is within the following spec. fsub=42 ± 2 kHz
SCHEMATIC DIAGRAM
� Original Service Manual page 7. (Location C � E, 6 � 8) Connection point
PRINTED WIRING BOARD
� Original Service Manual page 5. (Location A � C, 4 � 6)
oscilloscope frequency counter IN
