Kenwood TH-D74E Service Manual page 48

5.3 Failure diagnosis of the GPS section
Overview:
When the GPS function does not operate, use this flowchart to determine the problem.
Major parts for a GPS circuit
• GPS Connector(CN931)
• SAW Filter(FL931)
• Bluetooth/GPS IC (IC935)
• Level Converter IC (IC930)
• TCXO 19.2MHz (X930)
• 32.768kHz clock (X931)
IC702
MAIN MPU
Normal positioning fails.
Check that the location is suitable for sufficient GPS
signal reception ?
Yes
Check that the PCB and the patch antenna are connected
securely with a coaxial cable ?
Yes
Check the PCB
Check the PCB
Make a visual check on the matching circuit of the
antenna.
Side A: R946 and VA931; Side B: C973 and R947
When a normal
condition is confirmed.
When an abnormal
Check that the power supply
condition is confirmed.
voltage to the 33BT is 3.3 V.
Side A: L933 and L944: 3.3 V
When a normal
condition is confirmed.
When an abnormal
Check that the power supply
condition is confirmed.
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 power supply voltage of
the 30GPS is 3.0 V.
(Check with the GPS turned ON.)
Side B: L937: 3.0 V
When a normal
condition is confirmed.
1-48 (No.RA044<Rev.001>)
33BT 18BT 33BT
IC930
UART
UART
Level
converter IC
X930
TCXO
19.2MHz
No
No
When an abnormal
condition is confirmed.
Replace defective parts of the 33BT circuit as
necessary.
Side A: IC932 (33BT REG)
Side A: L933 and L944
Side A: C931, C937 and C980
Side B: C951, C952, C965 and C97
Replace defective parts of the 18BT circuit as
necessary.
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
Replace defective parts of the 30GPS circuit as
condition is confirmed.
necessary.
Side A: IC933 (30GPS REG)
Side A: C938
Side B: L937, C958 and C961
GPS module: (T9A-0037-00)
• 33BT Regulator (IC932)
• 18BT Regulator (IC931)
• 30GPS Regulator (IC933)
• MAIN MPU (IC702)
• GPS module (T9A-0037-00)
18BT
IC935
BT/GPS
IC
RF
Matching
X931
32.768kHZ
Clock
Receive the GPS signal in an open-sky area.
Connect the GPS antenna cable correctly. Otherwise, try
replacing the GPS antenna module (T9A-0037-00) or the
coaxial connector (Side B: CN931).
Replace defective parts, if any.
GPS
Module
T9A-0037-00
FL931
HPF
SAW
Filter
Filter
CN931
30GPS
Power
supply
When an abnormal
condition is confirmed. The BT/GPS (IC935) is
defective.
Replace the control PCB.
When an abnormal
condition is confirmed.
The MAIN MPU (IC702) is
defective.
Replace the control PCB.