Pa Adjustments; Driver Bias; Pa Bias - Codan X-2 Service Manual

Adjustments 7-10

7.11 PA Adjustments

7.11.1 Driver Bias

To check and adjust the driver bias:
1.
2.
3.
4.
5.

7.11.2 PA Bias

To check and adjust the output PA transistors bias:
1.
2.
3.
4.
5.
Disconnect exciter output to the PA by removing connector P2 on the
PA PCB assembly.
With the Transceiver off, unsolder Link DR (DC supply to the driver
transistors V13 and V14). Connect a Multimeter set to DC current
100 mA in place of the removed link (+ve to the right).
Switch on the Transceiver selected to any transmit channel and operate
the PTT (transmit mode). Check the driver current measures 18 mA
± 3 mA.
If the current is out of the specified limit stated in step 3 it can be
changed by selecting an alternative SOT resistor R39.
Switch off the Transceiver, disconnect Multimeter and replace Link
DR with a length of 22 gauge TCW.
Disconnect exciter output to the PA by removing connector P2 on the
PA PCB assembly.
With the Transceiver off, unsolder Fuse PA/OP (DC supply to the
output transistors V18 and V19). Connect a Multimeter, set to DC
current 1A, in place of the removed fuse (+ve to the left).
Switch on the Transceiver selected to any transmit channel and operate
the PTT (transmit mode). Check the output transistor current measures
120 mA ± 10 mA.
If the current is out of the specified limits stated above, adjust preset
potentiometer R45 [C5]
Switch off the Transceiver and replace Fuse PA/OP with three strands
taken from a piece of ribbon cable. Solder the wire to the two stakes
extending the centre of the wire up to form an inverted Vee. Only
solder at the wire ends attached to the stakes.
to the correct current level.
X-2 Technical Service Manual
Publication No: 15-02047