User Manual

SGD-SB2025NT-TUM, Part 1

Jan 12 Page 60 FAULT FINDING

3. The Micro Controller PCB requires specialised test software to check all the hardware input

and output ports. Please contact Simoco Customer Services and arrange for the Micro

Controller PCB to be returned to Simoco’s Service Centre.

7.3 R

ECEIVER

ODULE

7.3.1 VCO Locking.

1. In MxTools, check that all hardware settings are correct.

2. On the Rx Module, check the value of X3 (13 MHz or 14.4 MHz) is the same as the Rx

Reference Frequency in the ‘Hardware Settings’ on the MxTools configuration menu.

3. On the Microcontroller PCB, connect a Digital Voltmeter (DVM) to the Rx VCO TP and check

the Rx locking voltage is between 2 V – 18 V.

4. Check that +12 V (SKD-2) and 28 V (SKD-13) supply lines are present.

5. If the Rx locking voltage is out of specification, on the Rx VCO, slowly adjust CT1 a full 360°

and check for a change in the locking voltage.

6. If there is a change in the Rx VCO locking voltage, realign the VCO voltage to 9 V at the

centre frequency of the Rx band.

7. If there is no change in the Rx VCO locking voltage, check that the VCO supply voltage at

SKU-3 is approximately 7 V and, with an Oscilloscope, check the TCXO is oscillating on pin

8 of IC10.

8. If all the above tests fail, the VCO or IC10 may be faulty. Contact Simoco Customer

Services and arrange for the Rx Module to be returned to Simoco’s Service Centre.

7.3.2 Rx Front End

1. Solder a 2-way Berg header onto a flying coax lead. Remove solder link I near the mixer

(M1) and fit solder link J. Inject a RF signal into CN5. Check that the sensitivity is better

than –110 dBm.

2. If the sensitivity is OK past this point, check that the supply voltage to IC12 is approx. 8 V. If

the supply is OK, replace IC12. If this does not repair the Rx, the alignment may be incorrect

or other components on the front end may be faulty. Go to Section 6.2.2.

7.3.3 IF Section

1. If the Rx has low sensitivity past this point, increase the RF level to –60 dBm and ensure the

Rx DISC voltage is set to 2.50 V. If necessary, adjust L14 for the required voltage.

2. Connect a coax lead with a pickup loop around the end from the antenna input on the

HP8920A to the case of X1. Set the HP8920 to Tx test, change the Tune Mode to Manual

and change the centre frequency of the CTS to 44.545 MHz for A to B Band and 89.545 MHz

for C Band and above.

3. If CT1 cannot be adjusted to match the above frequencies, X1 may be faulty.

4. Set the centre frequency of the HP8920A to the Rx freq. + 45 MHz for A to B band or Rx

freq. + 90 MHz for C to M Band or Rx freq. – 90 MHz for N band and above.

5. Adjust the TCXO to within ± 20 Hz.

6. If the Rx centre frequency cannot be adjusted, the TCXO may be faulty.