NGT—Checks and adjustments
NGT Transceiver System Technical Service Manual 177
To adjust the driver bias:
1 Ensure the transceiver is switched off and the DC supply is disconnected.
1 Disconnect the exciter output from the PA by removing the connector from J2 (Tx
coaxial) on the RF/IF PCB in the RF unit (drawing 08-05261 (sheet 1) or 08-05889
(sheet 1)).
1 Unsolder the link labelled DR (DC supply to the driver transistors V207 and V208)
(see Figure 31 on page 162).
1 Set a multimeter to DC 20 mA range and connect it in place of the removed link.
1 Connect the DC supply, then switch on the transceiver.
1 Select any transmit channel, then hold down PTT.
1 Check that the driver current measures 13 mA ±2mA.
1 If the current is out of the specified limit stated above, change it by adjusting DR
BIAS (R222) (see Figure 31 on page 162).
1 Release PTT.
1 Switch off the transceiver, disconnect the multimeter, then replace the link with a
length of tinned copper wire.
To adjust the driver bias:
1 Ensure the transceiver is switched off and the DC supply is disconnected.
1 Disconnect the exciter output from the PA by removing the connector from J2 (Tx
coaxial) on the RF/IF PCB in the RF unit (drawing 08-05889 (sheet 1)).
1 Unsolder the link labelled DR (DC supply to the driver FETs V207 and V208) (see
Figure 32 on page 162).
1 Set a multimeter to DC 200 mA range and connect it in place of the removed link.
1 Connect the DC supply, then switch on the transceiver.
1 Select any transmit channel, then hold down PTT.
1 Check that the driver current measures 40 mA ±2mA.
ALTERNATIVE TEXT
Drawing 08-05869 (sheet 2)
NOTE
The transceiver must be in Service mode to make this adjustment (see
page 154, Accessing Service mode).
ALTERNATIVE TEXT
Drawing 08-06461 (sheet 2)
NOTE
The transceiver must be in Service mode to make this adjustment (see
page 154, Accessing Service mode).
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