Service manual

16
Alignment
Transmitter Output Power
Ë Set the transceiver to band center CH 2, and select high
power output.
Ë Ensure that the supply voltage is precisely 7.2 V, then
adjust VR3201 (while the PTT switch is pressed) for 5.0
W on the wattmeter, and confirm that supply current
remains below 2.2 A.
Ë Select low power output (“LO” displayed on the LCD),
and adjust VR3202 on the Main Unit for 1.1 W on the
wattmeter, and confirm that supply current remains
below 1.2 A.
Modulation Level
Ë With the transceiver set to band center CH 2, adjust the
AF generator for 77 mVrms output at 1 kHz to the MIC
jack.
Ë Press the PTT switch and adjust VR3204 on the Main
Unit for a deviation of ±4.3 kHz (for 25 kHz steps) or ±
2.1 kHz (for 12.5 kHz steps).
Ë Reduce the AF generator output to 7.7 mVrms.
Ë Press the PTT switch and adjust VR1002 on the Con-
trol Unit for a deviation of ± 3.0 kHz (for 25 kHz steps)
or ± 1.5 kHz (for 12.5 kHz steps).
PLL & Transmitter Alignment Points (II)
CTCSS Tone Level
Ë With the transceiver set to band center CH 2, set the
CTCSS encoder on .
Ë Press the PTT switch and adjust VR1001 on the CNTL
Unit for a deviation of ±0.7 kHz (for 25 kHz steps) or ±
0.35 kHz (for 12.5 kHz steps).
DTMF Tone Level
Ë With the transceiver set to band center CH 2.
Ë Press [1] key on the DTMF keypad while press and
holding the PTT switch, adjust VR1003 on the CNTL
Unit for a deviation of ±2.5 kHz (for 25 kHz steps) or ±
1.25 kHz (for 12.5 kHz steps).
AF Test Adapter Schematic
Ground
Attenuated
Test Output (1/2)
3.5
φ
PLUG
8Ω 1W
8Ω 1W
470µF
Note!
Because of the bridge audio amplifier circuit used in the
VX-520U, it is necessary to construct and use a simple
audio load test adapter as shown in the schematic dia-
gram above, when conducting receiver alignment steps.
Do not connect either side of the speaker leads to chassis
“ground”.
VR1002
VR1003
VR1001