Tait TP9100, Service Manual, Page: 229 / 326

TP9100 Service Manual
Transmitter Fault Finding 229
© Tait Electronics Limited May 2005
Task 7 —
Power and Current
are Skewed
If the RF output power and the supply current are skewed, the output
matching is suspect.
1. Remove the
PA BOT
can and
PA LPF BOT
can
.
2. Check that the PA output matching capacitor are in the correct
position as depicted in the latest BOM revision.
3. Go to Task 21 – the PIN switch and LPF require checking.
Task 8 —
Power and Current
are Low
If the RF output power and the supply current are uniformly low at all
frequencies, the PA is suspect or the input to the PA is reduced. Check the
circuitry of the PA (Q106) and the PA driver (Q103):
1. Enter the CCTM command 331 to check the DAC value of final
bias 1 (
CDC TX FIN RXAGC
). Record the value
x
returned.
2. Enter CCTM command 114 0 to turn off power control. Note the
current reading on the DC power supply. This is the bias current.
Table 10.4 shows the bias currents for each power setting.
3. Enter the CCTM command
32
to place the radio in receive mode.
4. If the current measured in Step 2 is correct, go to “Biasing of PA
Driver and PA” on page 230 . If not, go to Task 11 .
.
Table 10.4 PA bias currents in mA at different power levels
Frequency
band Very low
power Low
power Mid
power High
power
B1
200 200 200 200
H5
150 800 800 800
H6
200 800 800 900