Adjustments 7-4 X-2 Technical Service Manual
Publication No: 15-02047
7.6 VCO Checks and Adjustments
7.6.1 VCO1 Check
108-04840
There is no adjustment for VCO1 located on the Rx/Exciter & Control PCB
but a check can be made as follows:
1. Select Test Mode (refer to Section 7.5).
2. Select channel position 8 and USB/LSB to LSB.
3. Ensure the screening can is fitted over VCO1
[C4]
and Mixer 1 for the
following test.
4. Connect a DC voltmeter to TP3
[C4]
and check for a reading of 7.7 V
± 1.0 V. The frequency at TP4 should measure approximately
55 MHz.
5. Select channel position 9.
6. Check the voltage at TP3 reads 3.2 V ± 0.7 V. The frequency at TP4
should measure approximately 47 MHz.
7. Select channel position 10.
8. Check the voltage at TP3 reads 12.7 V ± 1.5 V. The frequency at TP4
should measure approximately 63 MHz.
9. Should any of the measurements not be within the stated limits, check
the VCO1 and associated circuits for possible faults.
7.6.2 VCO2 Check
108-04840
VCO2 located on the Rx/Exciter & Control PCB can be checked as follows:
1. Select Test Mode (refer to Section 7.5).
2. Select channel position 9 and USB/LSB to LSB.
3. Connect a DC voltmeter to TP13
[D6]
and check for a reading of
3.0 V ± 0.5 V. The frequency at TP10
[C7]
should measure
approximately 44.5405 MHz.
4. Select channel position 8.
5. Check the voltage at TP13 reads 8.0 V ± 1.5 V. The frequency at
TP10 should measure approximately 44.5445 MHz.
6. Select channel position 10.
7. Check the voltage at TP13 reads between 11.0–15.7V. The frequency
at TP10 should measure approximately 44.5485 MHz.
8. Should the measurements not be within the stated limits, adjust VCO2
as detailed in section 7.6.3 VCO2 Adjust.
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