4
TMR-RF975R
SECTION 3
ELECTRICAL ADJUSTMENTS
Transmission Frequency Check
1. Set the noise filter SW to OFF.
2. Input a signal of 1 kHz, 40 mVrms to only the L-CH (J402).
3. Connect a telescopic antenna to the frequency counter input
and extend the antenna to a length of approximately 8 cm.
4. Place TX-BASE board close to the frequency counter, then
measure the frequencies of CH1, CH2 and CH3 and make
sure the values are as follows:
CH1 : 913.5 MHz
±
200 kHz
CH2 : 914.0 MHz
±
200 kHz
CH3 : 914.5 MHz
±
200 kHz
When the frequency does not satisfy the specified value,
set the channel switch (S402) to CH2, then adjust the value of
the frequency counter to 914.0 MHz by trimmer capacitor in
the VCO unit.
Standard value :913.9MHz to 914.1MHz.
When completed with replacement, recheck the frequecies of
CH1, CH2 and CH3.
Compresser Output Check
1. Set the channel to CH2.
2. Input a signal of 1 kHz, 316 mVrms to L-CH and R-CH of
J402.
3. Measure IC 601 pin 7 and IC 602 pin 7 on the CHG-NR
board using a digital voltmeter (AC range) and put down a
value mesured. (Fig.1).
4. Input a signal of 1 kHz, 31.6 mVrms to L-CH and R-CH of
5. Measure IC 601 pin 7 and IC 602 pin 7 on the CHG-NR
±
6. When the frequency is not satisfied the specified value,
exchange TX- BASE board or CHG-NR board.
Setting :
Pilot Signal and MPX Signal Modulation Check and
Adjustment
1. Set the channel to CH2.
2. An electric wave is output for 5 or 10 minutes when OFF to ON
a power supply with no signal input (Power indicator will ON).
3. Set the RV402 and RV403 to max. (clockwise)
4. Connect a digital voltmeter (AC range) to the center terminal
of RV403 (Fig.2).
5. Adjust the value of the digital voltmeter to minimum by RV401.
6. See the RV402 to minimum. (counter clock wise)
7. Adjust the value of the digital voltmeter to max by L407.
8. Adjust the value of the digital voltmerter to 2.1to 2.6mVrms
by RV403.
9. Connect a digital voltmeter (AC range) with LPF to movable
terminal of RV403 (Fig.2).
10. Input a signal of 1 kHz, 316 mVrms to only the L-CH.
11. Adjust the value of the digital voltmeter to 5.2 to 6.4 mVrms
by RV402.
Connection points and Adjustment Location :
AF signal
generator
Telescopic
antenna
8 cm
L-CH / R-CH (J402)
TMR-RF975R
set
TMR-RF975R
set
Frequency counter
S402
J402
(L-CH) (R-CH)
CH3
←
CH2
←
CH1
VCO
UNIT
RV403
RV402
RV401
Hole
Sheet
L407
R464
IC 602
IC 601
1
8
4
5
1
8
4
5
CHG-NR board
+
–
digital
voltmeter
(AC range)
(Fig. 1)
7 pin
RV401-403,
L407
Modulation
check and
adjustment.
Trimmer capacitor:
Transmission
frequency
adjustment
+
–
digital
voltmeter
(AC range)
(Fig. 2)
R464
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