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Model
KX-TG6451CAT KX-TGA641RUT
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94
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3.14 MB
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PDF
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Service Manual
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Device
Telephone / DIGITAL CORDLESS PHONE
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kx-tg6451cat-kx-tga641rut.pdf
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Panasonic KX-TG6451CAT / KX-TGA641RUT Service Manual ▷ View online

41
KX-TG6451CAT/KX-TGA641RUT
9.3.
Troubleshooting by Symptom (Cordless Handset)
If your unit has below symptoms, follow the instructions in remedy column. Remedies depend on whether you have DECT tester
(*1) or not.  
Note:
(*1) A general repair is possible even if you don’t have the DECT tester because it is for confirming the levels, such as Acoustic
level in detail.
(*2) Refer to Check Point (Cordless Handset) (P.41)
9.3.1.
Check Point (Cordless Handset)
Please follow the items below when BBIC or EEPROM is replaced.
Note:
After the measuring, suck up the solder of TP.
*: Connections (P.55) is required beforehand.
The connections of adjustment equipments are as shown in Adjustment Standard (Cordless Handset) (P.57).
Items
Check 
Point
Procedure
Check or 
Replace Parts
(A)* 1.8 V Supply Adjustment
VDD1
1. Confirm that the voltage between test point VDD1 and GND is 1.8 V ± 0.02 V.
2. Execute the command “VDD”, then check the current value.
3. Adjust the 1.8 V voltage of VDD1 executing command “VDD XX“(XX is the
value).
IC1, Q2, C48, 
D1, C1, C44, 
R12, R45, 
C40, C45, F1
(B)*
BBIC Confirmation
-
1. BBIC Confirmation (Execute the command “getchk”).
2. Confirm the returned checksum value.
Connection of checksum value and program number is shown below.
IC1, X1, RA61, 
R64, R66
(C)* EEP-ROM Confirmation
-
1. EEPROM Confirmation (Execute the command “sendchar EPV”).
2. Confirm the returned value.
(Value for reference is written at ”EEPROM C/SUM” in
Software_Version_Table.xls)
Note:
“checksum” vary depending on the country version. You can find them in the
batch file, PNZZ- mentioned in The Setting Method of JIG (Cordless Handset)
(P.55).
IC1, IC3,  
R40~R42, 
C172
(D) Charge Control Check & 
Charge Current Monitor 
Check
-
1. Apply 3.5 V between CHG(+) and CHG(-) with DC power supply and set cur-
rent limit to 250 mA.
Confirm the indication of “charging” on LCD.
2. Confirm that the current limit LED of DC power supply is ON/OFF.
Confirm it after waiting over 1 minute at least.
3. Decrease current limit of DC power supply to 100 mA.
4. Confirm that the current limit LED of DC power supply is stable. (Current limiter
is ON.)
(If charge control cannot be confirmed by this procedure, please use battery to cord-
less handset power supply and try again.)
IC1, Q4 Q9, 
D7, R6, R7, 
F1, C1, R2, 
R30, R31, R8,  
R45
(E)* Charge Detection (OFF) 
Check
-
1. Stop supplying 3.5 V to CHG (+) and CHG (-).
2. Confirm the indication of “charging” has been cleared.
IC1, Q4 Q9, 
D7, R6, R7, 
F1, C1, R2, 
R30, R31, R8,  
R45
42
KX-TG6451CAT/KX-TGA641RUT
(F)* Battery Monitor Check
-
1. Apply 2.25 V between BATT+ and BATT-.
2. Execute the command 
sendchar PAD
sendchar LED 0
sendchar CRX 0 1
sendchar AD1
It assumes that the return value is XX.
a)  6c   XX   71: No need to adjust
b) XX: 6A ~ 6B: Need to adjust
XX: 72 ~ 74: Need to adjust
Write AD value of 2.25 V to EEPROM.
ex) read data: XX = 6A, write data: YY = 6A
read data: XX = 73, write data: YY = 73
EEPROM = 0004(Low Voltage) write “YY”
Execute the command “wreeprom 00 04 01 YY”.
EEPROM = 0005(No Voltage) write ‘’YY - 1D’’
Execute the command “×wreeprom 00 05 01 ZZ”.
EEPROM = 000A(Low Voltage BL) write “YY - 16”
Execute the command “wreeprom 00 0A 01 WW”.
Note:
ZZ = YY - C
No Voltage writing data limit is ‘00’.
c) XX: 00 ~ 69: Reject
XX: 75 ~ FF: Reject
IC1, F1, C1, 
R12, R45
(G)
Battery Low Confirma-
tion
-
1. Apply 2.40 V between BATT+ and BATT-.
2. Confirm that there is no flashing of Battery Icon.
3. Apply 2.25 V ± 0.08 V between BATT+ and BATT-.
4. Confirm that there is flashing of Battery Icon.
IC1, F1, C1, 
R12, R45
(H)* BBIC Clock Adjustment
CLK
1. Apply 2.6 V between BATT+ and BATT- with DC power.
2. Input Command “sendchar sfr”, then you can confirm the current value.
3. Check X’tal Frequency. (10.368 MHz ± 100 Hz).
4. If the frequency is not 10.368 MHz ± 100 Hz, adjust the frequency of CLK exe-
cuting the command “sendchar sfr xx xx (where xx is the value)” so that the
reading of the frequency counter is 10.368000 MHz ± 20 Hz.
Note:
Clear the registered information for Base Unit before measurement, because the
Frequency will not possibly get stable due to the registered information.
Pressing the button of “3” “7” “9” “#” clears the registration.
Register to it on Base Unit after measurement. 
IC1, X1, C47
 
(I)* Transmitted Power Con-
firmation
-
Remove the Antenna before starting step from 1 to 4.
1. Configure the DECT tester (CMD60) as follows;
<Setting>
• Test mode: PP
• RFPI: 0102030405
• Traffic Carrier: 5
• Traffic Slot: 4
• Mode: Loopback
• RF LEVEL = -70 dBm
• PACKET: PP32Z
2. Execute the command “sendchar TST 01 02 03 04 05".
3. Initiate connection from DECT tester.
4. Confirm that the NTP value at ANT is 19 dBm ~ 25 dBm.
IC1, 
C802~C806, 
C808~C814, 
C819~C820, 
C822, 
C825~C827, 
C834, 
C859~C864, 
L801~L804, 
DA801, 
R801~R808
(J)* Modulation Check and 
Adjustment
-
Follow steps 1 to 3 of (K).
4.Confirm that the B-Field Modulation is -370±30/ +370±30 kHz/div & Modulated
width   690 kHz using data type Fig 31.
IC1, 
C802~C806, 
C808~C814, 
C819~C820, 
C822, 
C825~C827, 
C834, 
C859~C864, 
L801~L804, 
DA801, 
R801~R808
Items
Check 
Point
Procedure
Check or 
Replace Parts
43
KX-TG6451CAT/KX-TGA641RUT
(K)* Frequency Offset Confir-
mation
-
Follow steps 1 to 3 of (I).
4.Confirm that the frequency Offset is < ± 50 kHz.
IC1, 
C802~C806, 
C808~C814, 
C819~C820, 
C822, 
C825~C827, 
C834, 
C859~C864, 
L801~L804, 
DA801, 
R801~R808
(L)* Frequency Drift Confir-
mation
-
Follow steps 1 to 3 of (I).
4.Confirm that the frequency Drift is < ± 35 kHz/ms.
IC1, 
C802~C806, 
C808~C814, 
C819~C820, 
C822, 
C825~C827, 
C834, 
C859~C864, 
L801~L804, 
DA801, 
R801~R808
(M)*
Sensitivity Receiver 
Confirmation
-
Follow steps 1 to 3 of (I).
4.Set DECT tester power to -88 dBm.
5.Confirm that the BER is < 1000 ppm.
IC1, 
C802~C806, 
C808~C814, 
C819~C820, 
C822, 
C825~C827, 
C834, 
C859~C864, 
L801~L804, 
DA801, 
R801~R808
(N)* Power RAMP Confirma-
tion
-
Follow steps 1 to 3 of (I).
4.Confirm that Power RAMP is matching.
IC1, 
C802~C806, 
C808~C814, 
C819~C820, 
C822, 
C825~C827, 
C834, 
C859~C864, 
L801~L804, 
DA801, 
R801~R808
(O) Audio Check and Confir-
mation
-
1. Link to BASE which is connected to Line Simulator.
2. Set line voltage to 48 V and line current to 40 mA.
3. Input -45 dBm (600
Ω)/1KHz to MIC and measure Line output level.
4. Confirm that the level is -5 dBm ± 2 dBm and that the distortion level is < 5 % at
TEL Line (600 
Ω Load).
5. Input -20 dBm (600
Ω)/1KHz to Line I/F and measure Receiving level at REV+
and REV-.
6. Confirm that the level is -20 dBm ± 2 dBm and that the distortion level is < 5 %
at Receiver. (vol = 2)
IC1, C12, D19, 
D20, C96, 
C97, R215, 
R27, RA4, 
C11, C13, 
R28, D3, D4, 
MIC, L9, RA2, 
R73, R74
(P) SP phone Audio Check 
and Confirmation
-
1. Link to Base which is connected to Line Simulator.
2. Set line voltage to 48 V and line current to 40 mA.
3. Set the cordless handset off-hook using SP-Phone key.
4. Input -25 dBm (600
Ω)/1KHz to Line I/F and measure Receiving level at SP+
and SP-.
5. Confirm that the level is -8.5 dBm ± 2 dBm and that the distortion level is < 5 %.
(vol = 3)
IC1, C12, C73, 
D13, D14, 
R152, R73, 
R74, RA2, 
MIC, C11, 
C13, RA4, 
R27, R28, 
R208, R209, 
C96, C97, 
R215, C72
(Q) Charge Pump 3.0V Sup-
ply Confirmation
CP3.0V
1. Confirm that the voltage between testpoint CP3.0 V and GND is 3.0 V -0.1/
+0.3V.
C52, C53, C49
(R) Charge Pump 4.0V Sup-
ply Confirmation
CP4.0V
1. Confirm that the voltage between testpoint CP4.0 V and GND is 4.0 V -0.2 V.
C50, C51
Items
Check 
Point
Procedure
Check or 
Replace Parts
44
KX-TG6451CAT/KX-TGA641RUT
9.3.2.
Troubleshooting for Speakerphone
When the customer’s telephone line corresponds to the following conditions, and the transmission signal of SP-Phone is inter-
rupted, performing the next set up to a cordless handset will improve it to some extent.
Conditions
1. When customer’s line has less line loss.
ex.) The customer is using optical fiber, ISDN terminal adaptor, or PBX.
In this case, receiving signal is strong and it may affect transmission signal.
2. When the other party is talking from noisy place.
ex.) The other party is using cellular phone. The background noise is very loud.
In this case, the noise from the other party (i.e. surrounding noise) may affect transmission signal.
Setting Method
• Change the cordless handset address of EEPROM (0129) from 00 to 01 by Engineering Mode.
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