Glenayre Document Number: 9110.01002
GL-T8541 PA
09/10/99
CHECKOUT AND MAINTENANCE
t8541
p7.
fdk
Copyright © 1997 Glenayre
Page: 7-9
D. The Q1 idle current should read 20 +/-5 mA. Refer to left side of Figure 7-6.
E.
Remove all power from the transmitter.
7.
Remove the meter from the test points
8.
Replace jumper JW1.
9.
Reconfigure the transmitter for normal operation.
7.7.3 Setting PA Board RF Transistor Bias
Use the following procedure to set the PA board bias.
1.
Remove power to the transmitter.
2.
Disconnect the exciter RF output cable.
3.
Remove PA module from transmitter and remove its outer and inner PA covers.
4.
Preset the bias potentiometer (R7) on each of the PA boards for minimum gate to
ground resistance. Refer to right side of Figure 7-6.
Note: If the driver board bias is to be set at this time, preset the driver board bias po-
tentiometers (R6 for Q1 and R16 for Q2) for minimum gate to ground resistance.
5.
Remove or relocate equipment as necessary to gain access to PA boards while PA
module is installed. Exciter must remain connected to metering board and dc power
source. Reinstall PA module leaving RF input disconnected.
6.
Apply power to the transmitter.
7.
Enter the forward power calibrate mode and key the transmitter (key sequence
m-5-6-1).
8.
Observing the VDT display, adjust R7 on each PA board for an idle current of 2A.
9.
Unkey the transmitter and press the escape key or “m” to exit the calibration mode.
10. If the driver board bias is to be adjusted at this time leave the PA installed as it is, if
not, proceed to step 11.
11. Remove all power and reconfigure the transmitter for normal operation.
7.7.4 Setting Driver Board RF Transistor Bias
1.
Remove power to the transmitter.
2.
Terminate the transmitter through an RF wattmeter and into a high power (at least 250
watt) RF test load. The wattmeter must be capable of measuring 250 watts.
3.
Disconnect the exciter RF output cable.
4.
Remove PA module from transmitter and remove its outer and inner PA covers.
5.
Preset the driver board bias potentiometers (R6 for Q1 and R16 for Q2) for minimum
gate to ground resistance.
6.
Remove or relocate equipment as necessary to gain access to PA boards while PA
module is installed. Exciter must remain connected to metering board and dc power
source. Reinstall PA module leaving RF input disconnected.
