TM8100/TM8200 Service Manual
Transmitter Fault Finding (40W/50W)
291
© Tait Electronics Limited
June 2006
Task 19 —
Biasing of PA Driver
—
DRV
test point
If there is no fault in the biasing of the PAs, investigate the biasing of the PA
driver (Q306). First check the
DRV
test point.
Important
Ensure that the current limit on the DC supply is 3A.
And, when entering the CCTM command
304
z
, do not
specify a value
z
higher than that recorded in
Failure to do so may result in the destruction of the
PA driver.
1.
Note the current reading on the DC power supply. As mentioned in
, the current will be less than 500mA.
2.
Enter the CCTM command
304
z
(where
z
was recorded in
)
to switch on the clamp current.
3.
Note the current reading on the DC power supply.
4.
Compare the above current readings. The current should increase by
an amount approximately equal to the offset given in
If it does, go to
5.
Check as follows that the voltage from the DAC is changing:
First enter the CCTM command
304 1
to switch off the bias.
6.
Measure the voltage at the
DRV
test point
(
CDC
TX
DRV
BIAS
)
(see
and
). The voltage should be:
7.
Enter the CCTM command
304
z
(where
z
was recorded in
)
to change the DAC value of the clamp current.
8.
The voltage should increase to:
9.
If the voltage does change, go to
. If it does not, go to
.
10.
Enter the CCTM command
32
to place the radio in receive mode,
and go to
“CODEC and Audio Fault Finding” on page 381
DRV test point: < 0.1V (after entry of CCTM 304 1)
DRV test point: 0.8 to 2.5V (after entry of CCTM 304
z
)
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...
