342
Transmitter Fault Finding (25W)
TM8100/TM8200 Service Manual
© Tait Electronics Limited
June 2006
12.3
Biasing of PA Driver and PAs
Introduction
The measurements of the transmitter RF output power in
might indicate a need to check the biasing of the two PAs and the
PA driver. The procedure is covered in this section. There are thirteen tasks
grouped as follows:
■
: prepare to check biasing
■
: check biasing of first PA
■
: check biasing of second PA
■
: check biasing of PA driver
■
: repair circuitry
The test and measurement points for diagnosing faults in the biasing of the
PAs and PA driver are summarized in
Task 12 —
Prepare to
Check Biasing
If the transmitter is not being inhibited, check the biasing of the two PAs
and the PA driver. First make the following preparations:
1.
Set the current limit on the DC power supply to 2A.
2.
Enter the CCTM command
331
to check the DAC value of final bias
1 (
CDC
TX
FIN
BIAS
1
) at maximum power. Record the value
x
returned.
3.
Enter the CCTM command
332
to check the DAC value of final bias
2 (
CDC
TX
FIN
BIAS
2
) at maximum power. Record the value
y
returned.
4.
Enter the CCTM command
304
to check the DAC value of the
clamp current at the driver gate. Record the value
z
returned.
5.
Enter the CCTM command
33
to place the radio in transmit mode.
6.
Switch off all biases by entering the following CCTM commands in
sequence:
■
331 1
■
332 1
■
304 1
■
114 1023
■
334 0
■
335 0
7.
Note the current reading on the DC power supply. This will be less
than 500mA.
8.
With the radio still in transmit mode, check the biasing of the PAs and
PA driver, beginning with
.
Summary of Contents for TM8235
Page 1: ...TM8100 mobiles TM8200 mobiles Service Manual MMA 00005 04 Issue 4 June 2006...
Page 10: ...10 TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 62: ...62 Description TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 148: ...148 Disassembly and Reassembly TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 162: ...162 Servicing Procedures TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 178: ...178 Interface Fault Finding TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 258: ...258 Receiver Fault Finding TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...
Page 446: ...446 Spare Parts TM8100 TM8200 Service Manual Tait Electronics Limited June 2006...