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2. ELECTRICAL ADJUSTMENTS
Note:
• Perform countermeasure for distortion before adjustments.
Adjust and confirm the unit by following procedure shown below after this countermeasure.
• Please adjust the transmitter and the headphone together.
Procedure for Measurements and Adjustments
Lastly, we would like to explain the procedure for adjusting this model. As this model adopts a Stereo Modulation method called “FM-
FM”, it is difficult to perform the adjustments with common measurement equipments.
The following adjustment should be performed with a spectrum analyzer.
Adjustments for Headphones
Reception frequency confirmation and adjustment
1) Prepare a pick-up coil (See the figure. 1) for measuring the local oscillation frequency of RX board.
Figure 1.
2) Turn on the power of the adjusted transmitter.
3) Input a signal of 1 kHz 50 mVrms to Lch of the transmitter for avoiding AUTO OFF.
4) Set the pick-up coil to the RX board as the figure. 2.
Figure 2.
5) Confirm and adjust the frequency by the spectrum analyzer.
CH1: Adjust CH1 to be the following value by turning CT41.
Adjusted value CH1=Main carrier frequency of Transmitter – (minus) 372.36 MHz
CH2: Adjust CH2 to be the following value by turning CT42.
Adjusted value CH2=Main carrier frequency of Transmitter – (minus) 372.36 MHz
BNC
Pick-up coil
One turn of
cupper wire
Diameter:
approx. 40 mm
coaxial cable
[RX Board] – Side A –
volume
IC41
CT42
CT41
spectrum
analyzer
pick-up coil
CH1: CT41
CH2: CT42
Be careful not to set the pick-up coil
too close to the RX board.
Summary of Contents for MDR-RF940R
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