Kenwood NX-720 Service Manual page 32

NX-720(G)/720
Failure diagnosis of the GPS section (Built-in GPS model only)
Overview: When the GPS function does not operate, use this fl owchart to determine the problem.
Note:
The transceiver supplies the voltage to the GPS antenna and the voltage is checked when the transceiver is turned "ON".
When the voltage is lower than the specifi ed value, "G ANT FAIL" is displayed for 2 seconds before entering user mode.
(At this time, the expected defect of the GPS antenna is a short. This error message does not appear when the expected de-
fect is an open .)
Positioning is not carried out normally.
When the power supply is turned
ON, "G ANT FAIL" is displayed.
When a normal
condition is confirmed.
Verify the connection of KRA-40.
(SMA connector)
When a normal
condition is confirmed.
Verify the connection of the SMA
connecting cable.
CN801 - E04-0492-05
When a normal
condition is confirmed.
Verify the supply voltage of the
KRA-40.
L802 : 3.0V
When a normal
value is confirmed.
Verify the backup voltage to the
GPS module.
L806 : 3.3V
When a normal
value is confirmed.
Verify the TXD data output from the
GPS module.
CN802 : Square wave form
When a normal
wave form is confirmed.
Verify the RXD data line.
D512 : Square wave form
When a normal
wave form is confirmed.
Verify the RF input signal line.
L801,C821,C824,R842,R843
When a normal
condition is confirmed.
ASIC IC is abnormal
or
KRA-40 is defective.
Replacing TX-RX Unit
■ TX-RX unit Information
Model Name
NX-720(G) (GPS model): E
NX-720: E
32
TROUBLE SHOOTING
When an abnormal
condition is
Power is not
confirmed.
supplied to the
KRA-40.
When an abnormal
condition is confirmed.
When an abnormal
condition is confirmed.
When an abnormal
Verify the power supply voltage
value is confirmed.
after removing the KRA-40.
When an abnormal
value is confirmed.
(The backup power supply is faulty. )
When an abnormal
The output of the GPS data is
wave form is confirmed.
IC801(5pin) : Square wave form
When an abnormal
wave form is confirmed.
(The RXD circuit is fauity.)
When an abnormal
condition is confirmed. (The signal line parts are faulty. )
Frequency Range [MHz]
136 - 174
136 - 174
Major parts for a GPS circuit
• GPS module (A801) : W02-3768-05
• Buffer IC (IC801)
• Filter (L801)
• GPS active antenna
Connect the KRA-40 correctly.
Connect the cable to the CN801
correctly.
When a normal
value is confirmed.
L802 : 3.0V
When an abnormal
value is confirmed.
Check IC 406 (33A).
When an abnormal
wave form is confirmed.
When a normal
wave form is
confirmed.
verified.
Replace D512.
Verify each part.
Original TX-RX unit Number
X57-8230-10
X57-8230-11
: TC7WH126FUF
: L79-1958-05
: KRA-40 (option)
(The KRA-40 may be broken)
Replace the KRA-40.
(The GPS power supply circuit may
be broken)
Check IC407 and its surrounding
parys.
(The GPS module may be broken)
Replas A801.
(The Buffer IC may be broken)
Replas IC801.
For Service TX-RX unit Number
X57-8230-12
X57-8230-13