– 5 –
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 “V
0
” 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 “V
0
”. (V1=V
0
×
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
4) Confirm the frequency is within the following spec.
fsub=42 ± 2 kHz
0.55 Vp-p
SCHEMATIC DIAGRAM
• Original Service Manual page 7.
(Location C – E, 6 – 8)
!
: Connection point
[TX Board]
PRINTED WIRING BOARD
• Original Service Manual page 5.
(Location A – C, 4 – 6)
+
–
oscilloscope
IN
frequency counter
OUT
coaxial cable
[TX Board] – Conductor Side –
^
