Check Biasing Of Second Pa - Tait TM9100 Service Manual

If the biasing of the first PA is correct, check that of the second PA (Q309).
Task 16 —
Check Biasing
of Second PA
Important
1.
2.
3.
4.
5.
6.
7.
278 Transmitter Fault Finding (50W/40W Radios)
Ensure that the current limit on the DC supply is 3A.
And, when entering the CCTM command 332 y, do not
specify a value y higher than that recorded in
Failure to do so might result in the destruction of the PAs.
Use the multimeter to measure the voltage at pin 8 of IC301
(see Figure 11.11 and Figure
pin 8 of IC301: < 100mV (initially)
Note the current reading on the DC power supply. As mentioned in
Step 7 of Task 12, the current will be less than 500mA.
Enter the CCTM command 332 y (where y was recorded in
Check that the voltage changes to:
pin 8 of IC301: 2 to 5V (after entry of CCTM 332 y)
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 332 1 to switch off final bias 2, and go to
Task 19.
Task
11.12). The voltage should be:
Table 11.6.
Step 7. If the voltage
Task 17. If neither the current
Task 18.
TM9100 Service Manual
© Tait Electronics Limited August 2005
12.
Task 12).