Check The Biasing Of The First Pa; Gate Biases For The Pas And Pa Driver At High Power - Tait TM9100 Service Manual

Check the biasing of the first PA (Q310).
Task 13 —
Check Biasing
of First PA
Important
1.
2.
3.
4.
5.
6.
7.
Table 11.6 Gate biases for the PAs and PA driver at high power
Frequency band
B1
H5
H7
TM9100 Service Manual
© Tait Electronics Limited August 2005
Ensure that the current limit on the DC supply is 3A.
And, when entering the CCTM command 331 x, do not
specify a value x higher than that recorded in
ure to do so might result in the destruction of the PAs.
Use a multimeter to measure the voltage at pin 14 of IC301
(see Figure 11.11 and
pin 14 of IC301: < 100mV (initially)
Note the current reading on the DC power supply. As mentioned in
Step 7 of Task 12, this will be less than 500mA.
Enter the CCTM command 331 x (where x was recorded in
Check that the voltage changes to:
pin 14 of IC301: 2 to 5V (after entry of CCTM 331 x)
Also note the current reading. This should increase by an amount
approximately equal to the offset given in
If the voltage and current are both correct, go to
is correct but not the current, go to
nor the voltage is correct, go to
Enter the CCTM command 331 1 to switch off final bias 1, and go to
Task 16.
First PA
1690
1800
1800
Transmitter Fault Finding (50W/40W Radios)
Figure 11.12). The voltage should be:
Table
Task 14. If neither the current
Task 15.
Offset currents in mA
Second PA
1690
1800
1800
Task 12. Fail-
Task 12).
11.6.
Step 7. If the voltage
PA driver
150
400
600
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