Kenwood NX-820H Service Manual page 33

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 an abnormal
condition is
confirmed.
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.
Replacing TX-RX Unit
TX-RX unit Information
Model Name
NX-820H(G) (GPS model) : K
NX-820H : K
NX-820H(G) (GPS model) : K2
NX-820H : K2
TROUBLE SHOOTING
Power is not
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.
L802 : 3.0V
When an abnormal
value is confirmed.
(The backup power supply is faulty. )
Check IC 406 (33A).
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.)
Replace D512.
When an abnormal
condition is confirmed. (The signal line parts are faulty. )
Verify each part.
Frequency Range Original TX-RX
[MHz] unit Number
450 - 520 X57-8240-10
450 - 520 X57-8240-11
400 - 470 X57-8240-12
400 - 470 X57-8240-13
NX-820H(G)/820H
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.
When an abnormal (The GPS power supply circuit may
value is confirmed.
When an abnormal
wave form is confirmed.
When a normal
wave form is
confirmed.
verified.
For Service TX-RX
unit Number
X57-8240-14
X57-8240-15
X57-8240-16
X57-8240-17
:TC7WH126FUF
:L79-1958-05
: KRA-40 (option)
(The KRA-40 may be broken)
Replace the KRA-40.
be broken)
Check IC407 and its surrounding
parys.
(The GPS module may be broken)
Replas A801.
(The Buffer may be broken)
Replas IC801.
33