Panasonic KX-TG2873BXS User manual

© 2006 Panasonic Communications Co., Ltd. All
rights reserved. Unauthorized copying and distribu-
tion is a violation of law.
ORDER NO. KM40607135CE
Telephone Equipment
KX-TG2873BXS
KX-TGA280BXS
Expandable Digital Cordless Answering
System
Silver Version
(for Asia, Middle Near East and Other areas )

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KX-TG2873BXS/KX-TGA280BXS

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KX-TG2873BXS/KX-TGA280BXS
TABLE OF CONTENTS
PAGE PAGE
1 Safety Precaution ------------------------------------------------ 4
1.1. For Service Technicians --------------------------------- 4
2 Warning -------------------------------------------------------------- 4
2.1. Battery Caution--------------------------------------------- 4
2.2. About Lead Free Solder (Pbf: Pb free)--------------- 4
3 Specifications ----------------------------------------------------- 6
4 Technical Descriptions ----------------------------------------- 7
4.1. FHSS Description ----------------------------------------- 7
4.2. Block Diagram (Base Unit_Main)---------------------- 8
4.3. Circuit Operation (Base Unit_Main)------------------- 9
4.4. Block Diagram (Cordless Handset) ------------------14
4.5. Circuit Operation (Cordless Handset) ---------------15
4.6. Circuit Operation (Charger Unit) ----------------------18
4.7. Signal Route -----------------------------------------------19
5 Location of Controls and Components ------------------21
5.1. Controls -----------------------------------------------------21
5.2. Display ------------------------------------------------------22
6 Installation Instructions ---------------------------------------23
6.1. Connections------------------------------------------------23
6.2. Battery Installation/Replacement ---------------------24
6.3. Battery Charge --------------------------------------------24
7 Operation Instructions-----------------------------------------26
7.1. Guide to Cordless Handset Programming ---------26
7.2. Dial Lock ----------------------------------------------------28
7.3. Error Messages -------------------------------------------29
7.4. Troubleshooting-------------------------------------------30
8 Test Mode ----------------------------------------------------------35
8.1. Test Mode Function (Base unit)-----------------------35
8.2. Test Mode Function (Cordless Handset) -----------36
9 Service Mode -----------------------------------------------------37
9.1. Service Mode Function (for Base Unit with
Cordless Handset) ---------------------------------------39
10 Troubleshooting Guide ----------------------------------------40
10.1. Troubleshooting Flow Chart ---------------------------40
10.2. How to Replace the Flat Package IC ----------------50
11 Disassembly and Assembly Instructions ---------------52
11.1. Disassembly Instructions -------------------------------52
11.2. Fix the LCD and the Receiver Guide to the
Main P.C.Board (Cordless Handset)-----------------57
12 Measurements and Adjustments---------------------------58
12.1. Things to Do after Replacing IC ----------------------58
12.2. The Setting Method of JIG (Base Unit) -------------59
12.3. The Setting Method of JIG (Cordless
Handset) ----------------------------------------------------60
12.4. Batch file Settings ----------------------------------------61
12.5. Commands -------------------------------------------------61
12.6. Adjustment of Base Unit --------------------------------62
12.7. Adjustment of Cordless Handset ---------------------63
12.8. Base Unit Reference Drawing-------------------------64
12.9. Cordless Handset Reference Drawing --------------65
12.10. Frequency Table ------------------------------------------66
13 Schematic Diagram ---------------------------------------------67
13.1. For Schematic Diagram---------------------------------67
13.2. Schematic Diagram (Base Unit_Main) --------------68
13.3. Schematic Diagram (Base Unit_Operation) -------72
13.4. Schematic Diagram (Base Unit_MIC) ---------------73
13.5. Schematic Diagram (Base Unit_Back Light)-------73
13.6. Schematic Diagram (Cordless Handset) -----------74
13.7. Schematic Diagram (Charger Unit)------------------ 76
13.8. For Signal Route ----------------------------------------- 77
14 Printed Circuit Board ------------------------------------------ 79
14.1. Circuit Board (Base Unit_Main) ---------------------- 79
14.2. Circuit Board (Base Unit_Back Light)--------------- 81
14.3. Circuit Board (Base Unit_Operation and MIC) --- 83
14.4. Circuit Board (Cordless Handset)-------------------- 85
14.5. Circuit Board (Charger Unit)--------------------------- 87
15 Appendix Information of Schematic Diagram--------- 88
15.1. CPU Data (Base Unit) ---------------------------------- 88
15.2. CPU Data (Cordless Handset)------------------------ 90
15.3. Terminal Guide of the Ics,Transistor and
Diodes ------------------------------------------------------ 92
16 Exploded View and Replacement Parts List ----------- 93
16.1. Cabinet and Electric Parts (Base Unit) ------------- 93
16.2. Cabinet and Electric Parts (Cordless Handset)--- 94
16.3. Cabinet and Electric Parts (Charger Unit) --------- 95
16.4. Accessories and Packing Materials ----------------- 96
16.5. Replacement Part List ---------------------------------- 98

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KX-TG2873BXS/KX-TGA280BXS
1 Safety Precaution
1.1. For Service Technicians
ICs and LSIs are vulnerable to static electricity.
When repairing, the following precautions will help prevent recurring malfunctions.
1. Cover plastic parts boxes with aluminum foil.
2. Ground the soldering irons.
3. Use a conductive mat on worktable.
4. Do not grasp IC or LSI pins with bare fingers.
2Warning
2.1. Battery Caution
1. Danger of explosion if battery is incorrectly replaced.
2. Replace only with the same or equivalent type recommended by the manufacturer.
3. Dispose of used batteries according to the manufacturer's Instructions.
2.2. About Lead Free Solder (Pbf: Pb free)
Note:
In the information below, Pb, the symbol for lead in the periodic table of elements, will refer to standard solder or solder that con-
tains lead.
We will use PbF when discussing the lead free solder used in our manufacturing process which is made from Tin (Sn), Silver
(Ag), and Copper (Cu).
This model, and others like it, manufactured using lead free solder will have PbF stamped on the PCB. For service and repair
work we suggest using the same type of solder.
Caution
• PbF solder has a melting point that is 50°F ~ 70°F (30°C ~ 40°C) higher than Pb solder. Please use a soldering iron with
temperature control and adjust it to 700°F ± 20°F (370°C ± 10°C).
• Exercise care while using higher temperature soldering irons.:
Do not heat the PCB for too long time in order to prevent solder splash or damage to the PCB.
• PbF solder will tend to splash if it is heated much higher than its melting point, approximately 1100°F (600°C).
• If you must use Pb solder on a PCB manufactured using PbF solder, remove as much of the original PbF solder as possible and
be sure that any remaining is melted prior to applying the Pb solder.
• When applying PbF solder to double layered boards, please check the component side for excess which may flow onto the
opposite side (See the figure below).

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KX-TG2873BXS/KX-TGA280BXS
2.2.1. Suggested PbF Solder
There are several types of PbF solder available commercially. While this product is manufactured using Tin, Silver, and Copper
(Sn+Ag+Cu), you can also use Tin and Copper (Sn+Cu), or Tin, Zinc, and Bismuth (Sn+Zn+Bi). Please check the manufac-
turer’s specific instructions for the melting points of their products and any precautions for using their product with other materi-
als.
The following lead free (PbF) solder wire sizes are recommended for service of this product: 0.3 mm, 0.6 mm and 1.0 mm.
2.2.2. How to Recognize that Pb Free Solder is Used
(Example: Cordless handset P.C.B.)
(Component View)
Note:
The location of the “PbF” mark is subject to change without notice.
IC700
IC460
IC2
IC1
IC301
PbF
1
Marke
d

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KX-TG2873BXS/KX-TGA280BXS
3 Specifications

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KX-TG2873BXS/KX-TGA280BXS
4 Technical Descriptions
4.1. FHSS Description
4.1.1. Frequency
The frequency range of 2.401 GHz - 2.482 GHz is used. Transmitting and receiving channel between Base Unit and Cordless
Handset is same frequency. Refer to Frequency Table (P.66).
4.1.2. FHSS (Frequency Hopping Spread Spectrum)
This telephone is using an IC chip which has similar specification to WDCT (World Digital Cordless Telephone) and is the tele-
phone system that can use multiple portable unit simultaneously. The explanation of this system is mentioned below. This sys-
tem uses a Time Division Multiple Access/Time Division Duplex (TDMA/TDD) scheme:
transmitting and receiving frequencies of the Base Unit and Cordless Handset are shared in the same frequency. The construc-
tion of RX/TX frequency data is shown below. It consists of 6 slots from the Base Unit to the Cordless Handset, and 6 slots from
the Handset to the Base Unit, total 12 slots in 10ms. By this slot system, simultaneous air link and communication between 6
Cordless Handset and the Base Unit can be realized. One communication between Cordless Handset and the Base Unit is
done by one slot from the Base Unit to Cordless Handset, and another slot from Cordless Handset to the Base Unit.
DSS makes spectrum spread by multiplying carrier signal by PN code. The purpose to make spectrum spread is to reduce
power density per time and per band. On the other hand, FHSS makes spectrum spread by changing channel every 10ms
according to Hopping table. Also the purpose to make spectrum spread is to reduce power density per time andper band.

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KX-TG2873BXS/KX-TGA280BXS
4.2. Block Diagram (Base Unit_Main)
HFMIC
FROM
DAB[0-15] AD[1-19, 21] RDN, WRN, /ROMCS
COL[0-4]
ROW[0-5]
LCD_CLK,LCD_TXD
LCDBL
ANSL
Q3
Q2
LCD_START, LCD_INH
RF3.45V
ANT1
ANT2
RXDA
TXDA PAON RSSI RXDSG
SYDA, SYCL, SYEN, SYRI
IC200
IC3
Extended I/O
Extended I/O
IC5
IC600
RF unit
DAB[0:7]
/IOCS
DAB[8:15]
/IOCS
IC501
CN1
HSIN
ODH1, ODH2
SPMUTE
+5.5VF
BB3.0V
BB3.0V
CN100
Line
*1: The excessive sound protection circuit
+
-
D102
DP
Q111 Q105, Q104
NHS HSIN
BELL
LINE_IN-, LINE_OUT
+VIN +5.5VF
+5V
RF3.45V
To Handset To Speaker
TG2873 BLOCK DIAGRAM (Base Unit_Main)
To operation unit
To antenna
ACFL
SP AMP
SPOUT
KEYTONE
CIDIN+ CIDIN-
HFMIC
IC302
Input : AC 220 V - 240 V 50/60 Hz Output : DC 6.5 V 500 mA
Q304
IC301
IC200
SPCNT
LSR-
LSR+
HSMIC-
HSMIC+
X2
10.368MHz
+5V
BB1.8V
BB3.0V
IC4
Q109, Q123, Q121
CN101 Q1
D7
IC300
IC201
Q120, Q901
IC100 Q110 PC100, PC101
Q407
DP Pulse SW Hook SW
Power Feeding Circuit
Automatic hold releasing circuit Parallel connection detection
Incoming call detection circuit
CID filter circuit Handsfree MIC Bias circuit
+5.5VF Power supply circuit DC/DC converter
To MIC unit
AC
adaptor
+5V Power supply circuit +3.45V Power supply circuit
Power failure detection circuit
Analog Voice Control Circuit
Ringer for power failure
*1: Excessive sound impact protection function with saturation characteristic
Q107, Q112 Q119, Q122

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KX-TG2873BXS/KX-TGA280BXS
4.3. Circuit Operation (Base Unit_Main)
General Description:
DSP is a digital speech/signal processing system that implements all the functions of speech compression and memory
management required in a digital telephone.
The DSP system is fully controlled by a host processor DSP. The host processor provides activation and control of all that func-
tions as follows.
4.3.1. DSP (Digital Speech/Signal Processing: IC4)
DTMF Detection/Generator
The DTMF detection is implemented by the DSP system in software. The DTMF detection is performed during Record, Play
back, and Line Monitoring modes of operation.
When the DTMF data from the Handset is received, the DTMF signal is output.
Caller ID demodulation
The DSP implements monitor and demodulate the FSK signals that provide CID information from the Central Office.
Analog Switching
The voice signal from telephone line is transmitted to the speaker or the voice signal from speakerphone microphone is transmitted
to the Telephone line, etc. They are determined by the signal path route operation of voice signal.
Block Interface Circuit
RF part, LED, Key scan, Telephone line.
4.3.2. FROM: IC501
FLASH-ROM stores base PROGRAM and following information data is stored.
Settings
ex: ID code, Flash Time, Tone/Pulse, TAM Message

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KX-TG2873BXS/KX-TGA280BXS
4.3.3. Power Supply Circuit
Function:
The power supply voltage from AC adaptor is converted to the desired voltage of each block.
Circuit Operation:
Q304 and IC302: +5.5V DCDC Converter
IC301 +5.0V Regulator
IC601 +3.45V Regulator
Q115 +3.0V IC4 I/O Voltage
Q114 +1.8V IC4 Internal Voltage
The voltage of +5V regulated in IC301 is controlled by IC4 to be made into IC4’s I/O voltage of BB3.0V at Q115 and IC4’s internal
power supply of BB1.8V at Q114.

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KX-TG2873BXS/KX-TGA280BXS
4.3.4. Reset Circuit
Function:
This circuit is used to initialize the microcomputer when it incorporates an AC adaptor.
Circuit Operation:
The system is reset when IC4’s BBIC internal voltage of BB1.8V goes down below 1.65V.

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KX-TG2873BXS/KX-TGA280BXS
4.3.5. Telephone Line Interface
Telephone Line Interface Circuit:
Function
• Ring signal detection
• Clip signal detection
• ON/OFF hook circuit
• Pulse dial circuit
• Side tone circuit
Ring signal detection:
In the standby mode, Q105 is open to cut the DC loop current and decrease the ring load. When ring voltage appears at the T (A)
and R (B) leads (When the telephone rings), the AC ring voltage is transferred as follows:
A →L101 →IC100 Pin 1
B →L101 →C106 →R109 →IC100 Pin 8
Ring signal from T-R is input to Ringer IC100 and output from pin 5 of IC100. Then it is detected through the following route.
IC100 5pin →R119 →PC100 →IC4 Pin 63 (BELL)
Clip (:Calling Line Identification presentation: Caller ID) signal detection:
The Clip signal voltage is transferred as follows;
A →L101 →C900 →R904 →C904 →R914 →IC4 Pin 107 (CIDin+)
B →L101 →C901 →R905 →C905 →R913 →IC4 Pin 112 (CIDin-)
ON/OFF HOOK Circuit:
Q104 is turned ON when IC4 detects the Ring signal, the handset of base unit is off-hook or the TALK key of the handset is
pressed. This causes Q105 to be turned ON and the line will be closed. (The Line Loop state).
A →L101 →D102 (3→1) →Q105 →Q109 →R126 →R179 →Q107 →D102 (4→2)→L101 →B [Line Loop]
Pulse Dial Circuit:
Pin 94 of DSP IC4 (HOOK/DP) turns Q104 ON/OFF to make the pulse dialing.
Side Tone Circuit:
Basically this circuit prevents the TX signal from feeding back to RX signal. As for this unit, TX signal feed back from Q109 is
canceled by the canceller circuit of DSP (IC4).

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KX-TG2873BXS/KX-TGA280BXS
4.3.6. Transmitter/Receiver
Base unit and handset mainly consist of RF Module and BBIC.
Base unit and handset transmit/receive voice signal and data signal through the antenna on carrier frequency.

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KX-TG2873BXS/KX-TGA280BXS
4.4. Block Diagram (Cordless Handset)
Receiver
RF_UNIT
IC700
ANT
X1
10.368MHz
EEPROM
IC2
LCD
Speaker
Charge Control
Q500
Q501
Q502
LCD_Light
LED2,3,4
Q101
D501
ANT_LED
KEY_Light
LED5,6,7,8,Q100
Power Circuit
IC300,IC301
Q300,Q301,Q302
MIC
Charge
Battery
+
+
-
-
BBIC
IC1
KEYS
KX-TGA280 BLOCK DIAGRAM (Cordless handset)

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KX-TG2873BXS/KX-TGA280BXS
4.5. Circuit Operation (Cordless Handset)
4.5.1. Construction
The circuit mainly consists of DSP and RF part as shown in the block diagram.
4.5.1.1. BBIC: IC1
Function:
• Battery Low, Power down detect circuit
• Ringer Generation
• Interface circuit (RF part, Speaker, Mic, LED, Key scan, LCD)
Initial waves:
4.5.1.2. RF part
Mainly voice signal is modulated to RF, or it goes the other way.
4.5.1.3. EEPROM : IC2
ALL setting data is stored.

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KX-TG2873BXS/KX-TGA280BXS
4.5.2. Power Supply Circuit
Circuit Operation:
When power on the Cordless Handset, the voltage is as follows;
BATTERY(2.2 V ~ 2.6 V: J1) →L502 →L300, D300 →Q300 (3.4 V) →Q302 (1.8 V), Q301 (2.5 V)

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KX-TG2873BXS/KX-TGA280BXS
4.5.3. Charge Circuit
Circuit Operation:
When charging the cordless handset on the Charger Unit, the charge current is as follows;
AC Adaptor: DC+(6.5V) →[R1, R2, R3, R4 →CHARGE+ (Charger)] →CHARGE+ (Cordless Handset) →Q502 →D501 →
L502 →BATTERY+ --- [Battery] --- BATTERY- →L503 →GND →R504 →CHARGE- (Cordless Handset) →[CHARGE-
(Charger) →GND] →DC- (GND)
In this way, the BBIC on Cordless Handset detects the fact that the battery is charged.
The charge current is controlled by switching Q500 of Cordless Handset.
4.5.4. Ringer and Handset SP-Phone

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KX-TG2873BXS/KX-TGA280BXS
4.5.5. Sending Signal
4.5.6. Battery Low/Power Down Detector
Circuit Operation:
“Battery Low” and “Power Down” are detected by BBIC which check the voltage from battery.
The detected voltage is as follows;
• Battery Low
Battery voltage: V (Batt) < 2.3V ± 50mV
The BBIC detects this level and " " starts flashing.
• Power Down
Battery voltage: V (Batt) < 2.1V ± 50mV
The BBIC detects this level and power down.
4.6. Circuit Operation (Charger Unit)
4.6.1. Power Supply Circuit
The power supply is as shown.

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KX-TG2873BXS/KX-TGA280BXS
4.7. Signal Route
Each signal route is as follows.

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KX-TG2873BXS/KX-TGA280BXS
Each signal route is as follows.