
LGE Internal Use Only
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
6. Trouble shooting
- 115 -
6.14.1 PAM Circuit
√
PAM circuit contains as below
- Band select switching circuitry (BS) to select GSM (Logic 0) and DCS/PCS (Logic1).
- VRAMP controls the level of output power for GMSK modulation and shape of Tx burst.
- For GMSK operation, set the PA_EN input High, and PA_MODE2 low(0.5v)
X= don’t care
√
When EGSM band called, it must seem as below.
Operational status
PA_EN
PA_BAND
PA_MODE2
TX_RAMP
Standby/PA off
0
X
X
X
Low Band GMSK Tx
1
0
0
Active
Low Band EDGE Tx
1
0
1
X
High Band GMSK Tx
1
1
0
Active
High band EDGE Tx
1
1
1
X
Is PAM
Control Signal
OK?
Replace
PCB
Check the next part
YES
NO
PAM Circuit
Is PAM Output
OK?
Replace
PAM
NO
Fig 14 Debugging flowchart of PAM circuit
Summary of Contents for KC550
Page 1: ...Date May 2008 Issue 1 0 Service Manual Model KC550 Service Manual KC550 Internal Use Only ...
Page 182: ...Note ...
Page 183: ...Note ...