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Kenwood NX-3720HG Service Manual page 164

Vhf digital transceiver, uhf digital transceiver
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Check the TX-RX UNIT PCB
Pass
Verify the BT/GPS control
signal (TXD2).
CN735 (15pin): Square
waveform UART data of 3.2V
logic.
Baud rate:
Default: 115.2kbps
After: 3.967Mbps.
Pass
Verify the BT/GPS control
signal (RXD2).
CN735 (14pin): Square
waveform UART data of 3.3V
logic.
Baud rate:
Default: 115.2kbps
After: 3.967Mbps.
Pass
[The BT/GPS IC is
abnormal]
Replace the PCB.
Descriptions of signal names
1) 33BT: BT/GPS IC 3.3V power supply
2) 18BT: BT/GPS IC 1.8V power supply
3) TXD2: BT/GPS serial data line connected to UART TX of MPU/DSP IC (MPU/DSP to BT/GPS IC)
4) RXD2: BT/GPS serial data line connected to UART RX of MPU/DSP IC (MPU/DSP to BT/GPS IC)
5) 18BT_HCI_RX: BT/GPS serial data line connected to UART RX of BT/GPS IC (MPU to BT/GPS IC)
6) 18BT_HCI_TX: BT/GPS serial data line connected to UART TX of GPS IC (BT/GPS IC to MPU)
7) /BT_SHUTDOWN: BT/GPS active control of MPU/DSP IC (MPU/DSP to BT/GPS IC) High Active, Low Reset
1-164 (No.RA054<Rev.001>)
Verify the BT/GPS control
Fail
signal (G_TXD2).
CP705 (3pin):
Square waveform UART data
of 3.2V logic.
[The RXD2 (18BT_HCI_TX)
line circuit is faulty]
Verify the CP705
Replace any abnormal parts.
Verify the BT/GPS control
Fail
signal (18BT_HCI_TX).
CP705, (4pin):
Square waveform UART data
of 1.8V logic.
[The RXD2 (18BT_HCI_TX)
line circuit is faulty]
Verify the CP705
Replace any abnormal parts.
Fail
Pass
Fail
Pass
[The MPU/DSP IC is
abnormal]
Replace the TX-RX PCB.
[The MPU/DSP IC is
abnormal]
Replace the TX-RX PCB.

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