— 8 —
13. Connect an AC voltmeter with LPF to speakers terminal (R+,R-).
14. Adjust the value of the AC voltmeter to specification by
headphones volume RV302.
Specified values: 155mVrms
15. Connect an AC voltmeter with LPF to speakers terminal (L+,L-).
16. Measure the value of the AC voltmeter.
17. Check the difference of the L and R to more than 25dB.
18. Remove a 33K
Ω
resistor between IC301 pin 4 and pin7.
Setting :
3-6. MPX Signal Modulation Check
1.
Set the transmitter CHANNEL switch to 2.
2.
Set the transmitter NOISE FILTER switch to OFF.
3.
Input a signal of 1kHz, 316mVrms to transmitter AUDIO IN-
A (L-ch) connector only.
4.
Connect an oscilloscope CH1 to speakers terminal (L+,L-) and
CH2 to IC301 pin 4 and GND.
5.
Push the headphones tuning switch (S301) to receive radio
frequency.
6.
Check the waveform of the oscilloscope that the CH1 is
demodulated 1kHz signal and CH2 is GND.
7.
Set the headphones volume (RV302) to max.
8.
Connect an AC voltmeter with LPF to speakers terminal (L+,L-).
9.
Check the value of the AC voltmeter to specification.
Specified values: 450mVrms to 650mVrms
Note:
When the specification is not satisfied in step 9, adjust
RV402 of the TMR-RF875R until the specification of 450
to 650mVrms is obtained.
Setting :
Adjustment Location : (See page 9)
+
–
Digital voltmeter
(AC range)
L+ / R+
L– / R–
+
–
+
–
L+
IC301 pin4
OSCILLOSCPE
L–
CH1
CH2
+
–
Digital voltmeter
(AC range)
L+
L–
+
–
+
–
L+
IC301 pin4
OSCILLOSCPE
L–
CH1
CH2
