Codan NGT 2010 RF Technical & Service Manual page 213

Drawing
ALTERNATIVE TEXT
NOTE
To adjust the bias of the PA output transistors:
1
1
1
1
1
1
1
1
1
NGT Transceiver System Technical Service Manual
08-05869 (sheet 2)
The transceiver must be in Service mode to make this adjustment (see
page 154, Accessing Service
Ensure the transceiver is switched off and the DC supply is disconnected.
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
(sheet 1)).
Unsolder the fuse PA O/P (F201) next to the power relay (DC supply to the output
transistors V211 and V212) (see
Set a multimeter to DC 1 A range and connect it in place of the removed fuse
(positive near to relay).
Connect the DC supply, then switch on the transceiver.
Select any transmit channel, then hold down PTT.
Check that the output current measures:
400 mA ±50 mA for 08-05869, or
•
• 400 mA ±20 mA for 08-06461
If the current is out of the specified limit stated above, change it by adjusting the
preset potentiometer PA BIAS (R239) (see
page 162).
Release PTT.
Switch off the transceiver, disconnect the DC supply, then resolder the fuse PA O/P.
If the fuse is broken, replace it with two strands (2 × 0.2 mm TCW) taken from a
piece of 7 × 0.2 mm cable. Extend the centre of the wire down from the two stakes
to form a V, ensuring it does not touch the PCB. Solder the wire to the two stakes,
making sure the solder does not run down the strand of wire (see
page 162 or Figure 32 on page
or 08-06461 (sheet 2)
mode).
Figure 31 on page 162
Figure 31 on page 162
162, PA Fuse).
NGT—Checks and adjustments
08-05261 (sheet 1) or
or Figure 32 on page
or Figure 32 on
Figure 31 on
08-05889
162).
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