KX-TG7851RUH, KX-TG7851RUJ, KX-TG7851RUR, KX-TG7852RU1, KX-TG7861RUH, KX-TG7861RUW, KX-TG7862RU2, KX-TGA785RUB, KX-TGA785RUH, KX-TGA785RUJ, KX-TGA785RUR, KX-TGA785RUW - Panasonic Telephone Service Manual (repair manual). Page 3

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1 Safety Precautions----------------------------------------------- 5

1.1. For Service Technicians --------------------------------- 5

2 Warning -------------------------------------------------------------- 5

2.1. Battery Caution--------------------------------------------- 5
2.2. About Lead Free Solder (Pbf:Pb free)---------------- 5

2.2.1. Suggested PbF Solder ------------------------------ 6

2.3. Discarding of P.C. Board--------------------------------- 6

3 Specifications ----------------------------------------------------- 7
4 Technical Descriptions ----------------------------------------- 8

4.1. Block Diagram (Base Unit) ------------------------------ 8
4.2. Circuit Operation (Base Unit) --------------------------- 9

4.2.1. Outline --------------------------------------------------- 9

4.3. Block Diagram (Base Unit RF Part)------------------10
4.4. Circuit Operation (Base Unit) -------------------------- 11

4.4.1. BBIC (Base Band IC: IC501) --------------------- 11
4.4.2. Flash Memory (IC601) (for KX-TG7861

only) ----------------------------------------------------- 11

4.4.3. EEPROM (IC611) ------------------------------------ 11
4.4.4. Power Supply Circuit--------------------------------12
4.4.5. Telephone Line Interface---------------------------13
4.4.6. Transmitter/Receiver--------------------------------13

4.5. Block Diagram (Handset)-------------------------------14
4.6. Circuit Operation (Handset)----------------------------15

4.6.1. Outline --------------------------------------------------15
4.6.2. Power Supply Circuit/Reset Circuit--------------15
4.6.3. Charge Circuit ----------------------------------------15
4.6.4. Battery Low/Power Down Detector--------------15
4.6.5. Speakerphone ----------------------------------------15

4.7. Signal Route -----------------------------------------------16

5 Location of Controls and Components ------------------18
6 Installation Instructions ---------------------------------------18
7 Operating Instructions-----------------------------------------18

7.1. For Service Hint-------------------------------------------18

8 Service Mode -----------------------------------------------------19

8.1. Engineering Mode ----------------------------------------19

8.1.1. Base Unit ----------------------------------------------19
8.1.2. Handset ------------------------------------------------21

8.2. EEPROM LAYOUT (Handset)-------------------------23

8.2.1. Scope ---------------------------------------------------23
8.2.2. Introduction--------------------------------------------23
8.2.3. EEPROM contents ----------------------------------23

8.3. How to Clear User Setting------------------------------24

8.3.1. Resetting both base unit and handset----------24
8.3.2. Resetting only handset -----------------------------24

9 Troubleshooting Guide ----------------------------------------25

9.1. Troubleshooting Flowchart -----------------------------25

9.1.1. Check Power------------------------------------------26
9.1.2. Check Battery Charge ------------------------------27
9.1.3. Check Link---------------------------------------------28
9.1.4. Check the RF part -----------------------------------31
9.1.5. Check Handset Transmission --------------------34
9.1.6. Check Handset Reception-------------------------34
9.1.7. Check Caller ID --------------------------------------34
9.1.8. Bell Reception ----------------------------------------35
9.1.9. Check TAM Operation (for KX-TG7861

only) -----------------------------------------------------35

9.2. Troubleshooting by Symptom (Base Unit and

Charger Unit) ----------------------------------------------36

9.2.1. Check Point (Base Unit) --------------------------- 36

9.3. Troubleshooting by Symptom (Handset)----------- 38

9.3.1. Check Point (Handset)----------------------------- 38
9.3.2. Troubleshooting for Speakerphone ------------- 41

10 Disassembly and Assembly Instructions--------------- 42

10.1. Disassembly Instructions------------------------------- 42

10.1.1. Base Unit ---------------------------------------------- 42
10.1.2. Handset------------------------------------------------ 45
10.1.3. Charger Unit ------------------------------------------ 46

10.2. How to Replace the Handset LCD------------------- 47

11 Measurements and Adjustments -------------------------- 48

11.1. Equipment Required ------------------------------------ 48
11.2. The Setting Method of JIG (Base Unit) ------------- 48

11.2.1. Connections ------------------------------------------ 48
11.2.2. How to install Batch file into P.C. ---------------- 49
11.2.3. Commands-------------------------------------------- 49

11.3. Adjustment Standard (Base Unit) -------------------- 50

11.3.1. Bottom View ------------------------------------------ 50

11.4. The Setting Method of JIG (Handset)--------------- 51

11.4.1. Connections ------------------------------------------ 51
11.4.2. How to install Batch file into P.C. ---------------- 52
11.4.3. Commands-------------------------------------------- 52

11.5. Adjustment Standard (Handset) ---------------------- 53

11.5.1. Component View ------------------------------------ 53

11.6. Things to Do after Replacing IC or X'tal ------------ 54

11.6.1. How to download the data ------------------------ 54

11.7. RF Specification ------------------------------------------ 56

11.7.1. Base Unit ---------------------------------------------- 56
11.7.2. Handset------------------------------------------------ 56

11.8. How to Check the Handset Speaker or

Receiver ---------------------------------------------------- 57

11.9. Frequency Table (MHz)--------------------------------- 57

12 Miscellaneous---------------------------------------------------- 58

12.1. How to Replace the Flat Package IC --------------- 58

12.1.1. Preparation-------------------------------------------- 58
12.1.2. How to Remove the IC----------------------------- 58
12.1.3. How to Install the IC -------------------------------- 59
12.1.4. How to Remove a Solder Bridge ---------------- 59

12.2. How to Replace the Shield Case--------------------- 60

12.2.1. Preparation-------------------------------------------- 60
12.2.2. Caution------------------------------------------------- 60
12.2.3. How to Remove the Shield Case---------------- 60
12.2.4. How to Install the Shield Case ------------------- 61

12.3. Terminal Guide of the ICs, Transistors, Diodes

and Electrolytic Capacitors ---------------------------- 62

12.3.1. Base Unit ---------------------------------------------- 62
12.3.2. Handset------------------------------------------------ 62

13 Schematic Diagram -------------------------------------------- 63

13.1. For Schematic Diagram -------------------------------- 63

13.1.1. Base Unit (Base Unit (Main))--------------------- 63
13.1.2. Handset (Handset)---------------------------------- 63

13.2. Base Unit (Main) ----------------------------------------- 64

13.2.1. KX-TG7851RU--------------------------------------- 64
13.2.2. KX-TG7861RU--------------------------------------- 66

13.3. Base Unit (Operation) (KX-TG7861 only)---------- 68
13.4. Handset----------------------------------------------------- 70

14 Printed Circuit Board ------------------------------------------ 73

14.1. Base Unit (Main) ----------------------------------------- 73