DOWNLOAD Panasonic KX-TG7851UAB / KX-TG7851UAH / KX-TG7861UAB / KX-TGA785RUB / KX-TGA785RUH Service Manual ↓ Size: 6.65 MB | Pages: 88 in PDF or view online for FREE

33

(*1) Refer to Adjustment Standard (Base Unit) (P.50)
(*2) Refer to Adjustment Standard (Handset) (P.53)

No.

Item

BU (Base Unit) Check

HS (Handset) Check

1

Link Confirmation Normal

HS, BU Mode: [Normal mode]

1. Register Regular HS to BU (to be 

checked).

2. Press [Talk] key of the Regular HS to 

establish link.

1. Register HS (to be checked) to Regular 

BU.

2. Press [Talk] key of the HS to establish link.

2

X’tal Frequency confirmation

HS, BU Mode: [Test mode]

1. Check X’tal Frequency. (*1)

(10.368 MHz ± 100 Hz)

1. Check X’tal Frequency. (*2)

(10.368 MHz ± 100Hz)

3

Range Confirmation Normal

HS, BU Mode: [Normal mode]

1. Register Regular HS to BU (to be 

checked).

2. Press [Talk] key of the Regular HS to 

establish link.

3. Compare the range of the BU (being 

checked) with that of the Regular BU.

1. Register HS (to be checked) to Regular 

BU.

2. Press [Talk] key of the HS to establish link.
3. Compare the range of the HS (being 

checked) with that of the Regular HS.

34

How to Check the Handset Speaker or Receiver (P.57).
Signal Route (P.16)

OK

Check MIC of Handset.

Check CDL TX (HANDSET) in Signal Route.

Check Handset Speaker in How to check the Handset 
Speaker or Receiver.

OK

Check CDL RX (HANDSET) in Signal Route.

Check Caller ID in Signal Route.

35

*1 TG7861 only

Telephone Line Interface (P.13)
Check Link (P.28)
How to Check the Handset Speaker or Receiver (P.57)

(*1) When replacing FLASH MEMORY (IC601), TAM data need to be written to it. Refer to Base Unit of Things to Do after
Replacing IC or X'tal (P.54)

When bell signal is coming, is there bell sound 
signal at BBIC (IC501:CIDINp, CIDINn)?

NO

Check around IC501 (VDD_PA), C506, C472, C473, 
C476, C477, C478, C479

YES

Check around C103, C104, C105, C106, C107, 
C108, C109, C110, C111, C112, C123, C124, 
R101, R102, R103, R104, R105, R106, R107, R108, 
R109, R110, R111, R112, P101

NO

When bell signal is coming, is there bell sound 
signal at IC501 (SPP, SPN)?

*1

Does the bell sound from SPEAKER?

Check around SP+, SP- .

When bell signal coming, is there bell sound signal 
at BBIC (IC1: 35, 37)?

NO

NO

YES

When bell signal coming, is there bell sound signal
at SP+, SP- ?

YES

Check BBIC (IC1), C78, C79, C73, C72, D13, 
D14, R77, R76.

NO

Check cable of SPEAKER and resistance value
of SPEAKER.

Check IC601 and BBIC (IC501) of Base Unit. (*1)

Is there a TAM icon on the Handset display?

Turn on the Answering System.

Check Power Supply Circuit.

NO

NO

YES

Is the voltage of VBAT of Base Unit about 3.0 V
and VDD1 about 1.8 V, VDD4 about 3.0 V, 
VDD5 about 3.0 V?

YES

36

If your unit has below symptoms, follow the instructions in remedy column. Remedies depend on whether you have DECT tester
(*1) or not. 

(*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 (Base Unit) (P.36)

Please follow the items below when BBIC or EEPROM or FLASH is replaced.

After the measuring, suck up the solder of TP.
*: The Setting Method of JIG (Base Unit) (P.48) is required beforehand.
The connections of simulator equipment are as shown in Adjustment Standard (Base Unit) (P.50).

Symptom

Remedy (*2)

You don’t have DECT Tester.

You have DECT Tester. 

(Model Number: CMD60)

You cannot dial.

Check item (A) - (I), (R).

Check item (A) - (I), (J) - (N), (R).

You cannot hear the caller’s voice.

Check item (A) - (G), (O), (R).

Check item (A) - (G), (J) - (N), (O), (R).

You cannot use the handset a little away from base unit even if the
handset is within range of the base unit.

-

Check item (J) - (N).

The acoustic transmit level is high or low.

Check item (O).

Check item (O).

The acoustic reception level is high or low.

Check item (O).

Check item (O).

Base unit and handset do not link to each other.

Check item (A) - (I).

Check item (A) - (N).

The unit cannot charge.

Check item (P).

Check item (P).

TAM does not work. (for KX-TG7861 only)

Check item (Q).

Check item (Q).

Items

Check 

Point

Procedure

Check or 

Replace Parts

(A)

3.0 V Supply 
Confirmation

VBAT

1. Confirm that the voltage between test point VBAT and GND is 3.0 V ± 0.2 V.

IC302, R321, 

R322, C341, 

C342 

(B)

1.8 V Supply 
Confirmation

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 1.8V voltage of VDD1 executing command “VDD XX“(XX is the

value).

Q301, IC501, 

R311, C311, 

C516, C519

(C) Charge Pump 3.0V

Supply Confirmation

VDD5

1. Confirm that the voltage between test point VDD5 and GND is 3.0 V -0.1/+0.3

V. 

IC501, C511

(D) Charge Pump 3.0V

Supply Confirmation

VDD4

1. Confirm that the voltage between test point VDD4 and GND is 3.0 V ± 0.2 V. 

IC501, C509, 

R507

(E)*

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.

IC501, X501

(F)* EEPROM Confirmation

-

1. EEP-ROM 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).

IC501, RA611, 

IC611, C611

(G)* BBIC Clock Adjustment

CKM

1. Confirm that the voltage between testpoint VDD4 and GND is less than 1.0 V.
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 CKM

executing the command “sendchar sfr xx xx (where xx is the value)” so that
the reading of the frequency counter is 10.368000 MHz ± 5 Hz.

IC501, X501, 

C502

(H)* Hookswitch Check with 

DC Characteristics

-

1. Connect Telephone Socket to Tel-simulator which is connected with 600 

.

2. Set line voltage to 48 V and line current to 40mA at off-hook condition of

normal telephone.

3. Execute the command “hookoff”
4. Confirm that the line current is 40 mA ± 5 mA.
5. Execute the command “hookon”.
6. Confirm that the line current is less than + 0.8 mA.

P101, Q141, 
R141, R142, 
Q142, R144, 
R145, D101, 
R161~R167, 
D141, Q161, 
R151, IC501

checksum value

02D9

program number

DDD1EN

ex.)