Kenwood TH-D74E Service Manual page 47

When a normal
condition is confirmed.
Check reference CLK: X930 of the BT/GPS.
(Check with the BT turned ON).
Side B: Between C939 and C940:
Sine waves, 19.2 MHz,
0.2 to 1.2Vp-p
When a normal
condition is confirmed.
Check the BT control signal
(18BT_HCI_RX).
Side B: RA935 (pin 3)
Square wave UART data (1.8 V)
Baud rate:
Access: 115.2 kbps
Normal: 3.56923 Mbps
When a normal
condition is confirmed.
Check the BT control signal (RXD2).
Side A: RA932 (pin 8)
Square wave UART data (3.3 V)
Baud rate:
Access: 115.2 kbps
Normal: 3.56923 Mbps
When a normal
condition is confirmed.
Check the RTC circuit of the BT/GPS.
X931 (pin 3): Square wave,
32.768kHz,1.8Vp-p
When a normal
condition is confirmed.
The BT/GPS (IC935) is defective.
Replace the control 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 (UART)(IC702(MAIN MPU) → IC936(LEVEL CONVERTER))
(4) RXD2:BT/GPS serial data line (UART)(IC936(LEVEL CONVERTER) → IC702(MAIN MPU))
(5) 18BT_HCI_RX:Serial data line (UART)(IC936(LEVEL CONVERTER) → IC935(BT/GPS IC))
(6) 18BT_HCI_TX:Serial data line (UART)(IC935(BT/GPS IC) → IC936(LEVEL CONVERTER))
(7) /BT_SHUTDOWN:BT active control (IC702(MAIN MPU) → IC935(BT/GPS IC)) High Active, Low Reset
Replace defective parts of the reference generation
When an abnormal
circuit of BT/GPS as necessary.
condition is confirmed.
Side A: Q930, R935, R936 and RA938
Side B: X930, C935, C939 and C940
When an abnormal
Replace the RA935. Check the BT control signal
condition is confirmed.
(TXD2) if the condition does not return to normal.
Side A: RA932 (pin 7)
Square wave UART data (3.3 V)
The 18BT_HCI_RX (TXD2) line is defective.
Side A: RA932
Side B: Replace the IC936 and R945 as necessary.
When an abnormal
Replace the RA932. Check the BT control signal
condition is confirmed.
(18BT_HCI_TX) if the condition does not return to
normal.
Side B: RA395 (pin 4)
Square wave UART data (1.8 V)
The RXD2 (18BT_HCI_TX) line is defective.
Side B: Replace the RA935 and
IC936 as necessary.
When an abnormal
condition is confirmed.
When an abnormal
condition is confirmed.
When an abnormal
condition is confirmed.
When a normal
condition is confirmed.
When an abnormal
condition is confirmed.
When a normal
condition is confirmed.
Check the RTC circuit of the BT/GPS.
Replace the X931, L939 or C971 if any defects are found in
X931, L939 or C971.
The BT/GPS (IC935) is defective.
Replace the control PCB.
The MAIN MPU (IC702) is
defective.
Replace the control PCB.
The BT/GPS (IC935) is defective.
Replace the control PCB.
(No.RA044<Rev.001>)1-47