Kenwood TH-D74E Service Manual page 46

5.2 Failure diagnosis of the Bluetooth section
Overview:
When the Bluetooth function does not operate, use this flowchart to determine the problem.
Major parts for a Bluetooth circuit
• Bluetooth antenna
• LC filter (FL932)
• Bluetooth/GPS IC (IC935)
• Level converter (IC936)
• Level converter (IC937)
IC702
MAIN MPU
The transceiver does not pair with a Bluetooth (BT) headset.
Check that the built-in battery of the BT headset has a sufficient
remaining capacity?
Check that the BT headset is turned power ON?
Check that the BT headset is in pairing mode?
Yes
Check that the PCB is not in contact with the BT antenna
and that the antenna is not deformed.
(Check the presence of the contact trace of the
BT antenna on the land.)
When a normal
condition is confirmed.
Check the PCB.
Check the PCB.
Make a visual check on the matching circuit of
the antenna.
Side A: L942, C977, C983 and
C982; Side B: FL932 and C969
When a normal
condition is confirmed.
Check that the power supply
voltage to the 33BT is 3.3 V.
Side A: L933 and L944: 3.3 V
When a normal
condition is confirmed.
Check that the power supply
voltage to the 18BT is 1.8 V.
Side A: L934 and L943: 1.8 V
When a normal
condition is confirmed.
Check that the 18BT control signal
(/BT_SHUTDOWN) is at 1.8 V.
(Check with the BT turned ON).
Side A: RA937
(pin 4 on the upper right-hand side)
: 1.8 V
When a normal
condition is confirmed.
1-46 (No.RA044<Rev.001>)
18BT
33BT
IC936
UART UART
Level
converter IC
33BT 18BT
IC930
PCM
PCM
Level
converter IC
19.2MHz
No
When an abnormal
condition is confirmed.
When an abnormal
condition is confirmed.
Replace defective parts of the 33BT circuit
When an abnormal
as necessary.
condition is confirmed.
Side A: IC932 (33BT REG)
Side A: L933 and L944
Side A: C931, C937 and C980
Side B: C951, C952, C965 and C976
Replace defective parts of the 18BT circuit as
When an abnormal
necessary.
condition is confirmed.
Side A: IC931 (18BT REG)
Side A: L934 and L943
Side A: C930, C933 and C944
Side B: C949, C963, C975 and C981
When an abnormal
condition is confirmed.
• TCXO 19.2MHz (X930)
• 32.768kHz clock (X931)
• 33BT Regulator (IC932)
• 18BT Regulator (IC931)
• MAIN MPU (IC702)
18BT
33BT
IC935
BT/GPS
IC
FL932
LC
Filter
X931
X930
TCXO
32.768kHZ
Clock
Charge the BT headset.
Turn ON and bring the BT headset within a distance of
1 to 2 m from the transceiver.
Retry pairing the transceiver with the BT headset.
Build in the BT antenna correctly.
If the antenna has a defect, replace the corresponding parts.
Replace defective parts, if any.
When an abnormal
condition is confirmed.
When an abnormal
condition is confirmed.
Replace the RA937. The MPU/DSP
(IC702) is defective if the
condition does not return to normal.
Replace the control PCB.
Bluetooth
Antenna
Bar Spring
The BT/GPS (IC935) is defective.
Replace the control PCB.
The BT/GPS (IC935) is defective.
Replace the control PCB.