Sony SPP-M920 Service manual

SPP-M920

SERVICE

MANUAL

US Model

SPECIFICATIONS

MICROFILM

CORDLESS TELEP0HONE

TABLE OF CONTENTS

Specifications ........................................................................... 1

1. GENERAL

Location and Function of Controls .................................... 3

Read this first ..................................................................... 4

Step 1 : Checking the package contents............................. 4

Step 2 : Setting up the base phone ..................................... 4

Step 3 : Preparing the battery pack for the handset ........... 5

Making calls....................................................................... 5

Receiving calls ................................................................... 6

Changing the ringer type.................................................... 7

Speed dialing...................................................................... 7

Talking between the phones (intercom) ............................. 8

Switching the phones durig a call ...................................... 8

Conference calls................................................................. 8

Caller ID service ................................................................ 8

Mounting the base phone on a wall ................................. 10

Notes on power sources ................................................... 10

Maintenance ..................................................................... 10

2. DISASSEMBLY

2-1. Battery Pack Removal ...............................................11

2-2. Hand Cabinet (Rear) Removal ..................................11

2-3. Antenna Removal ..................................................... 12

2-4. Hand Main Board Removal ...................................... 12

3. CIRCUIT OPERATION................................................. 13

4. TEST MODE .................................................................. 19

5. ADJUSTMENTS

5-1. Base Unit Section ..................................................... 22

5-2. Handset Section ........................................................ 24

6. DIAGRAMS

6-1. Explanation of IC Terminals..................................... 26

6-2. Block Diagrams ........................................................ 29

6-3. Printed Wiring Boards (Base Key Section) .............. 35

6-4. Schematic Diagram (Base Key Section) .................. 37

6-5. Schematic Diagram (Base Unit Section) .................. 42

6-6. Printed Wiring Boards (Base Unit Section).............. 47

6-7. Printed Wiring Boards (Handset Section) ................ 52

6-8. Schematic Diagram (Handset Section)..................... 55

7. EXPLODED VIEWS

7-1. Base Unit Section ..................................................... 58

7-2. Handset Section ........................................................ 59

8. ELECTRICAL PARTS LIST ........................................ 60

Flexible Circuit Board Repairing

• Keep the temperature of the soldering iron around 270°C during repairing.

• Do not touch the soldering iron on the same conductor of the circuit board (within 3 times).

• Be careful not to apply force on the conductor when soldering or unsoldering.

Notes on chip component replacement

• Never reuse a disconnected chip component.

• Notice that the minus side of a tantalum capacitor may be damaged by heat.

SAFETY-RELATED COMPONENT WARNING!!

COMPONENTS IDENTIFIED BY MARK ! OR DOTTED LINE WITH MARK ! ON THE SCHEMATIC DIAGRAMS AND IN THE PARTS LIST ARE CRITICAL TO SAFE OPERATION. REPLACE THESE COMPONENTS WITH SONY PARTS WHOSE PART NUMBERS APPEAR AS SHOWN IN THIS MANUAL OR IN SUPPLEMENTS PUBLISHED BY SONY.

Notes when repairing/replacing the microcomputer (Base Unit : IC8, Handset : IC11)

The microcomputer for this equipment initial used an externally installed ROM version but incorporation of internal software (in-

ternal ROM version) led to elimination of the externally installed ROM version. The internal ROM version is available as a service part. When replacing or servicing this part, the following parts must also be replaced along with it. (only when set with the external installed ROM version).

1. HANDSET IC3, 4 ; Deleted (These were never available as service) parts. R81 (10k) Deleted R79 (10k) Added

2. BASE UNIT IC12, 13 ; Deleted (These were never available as service) parts. R140 (10k) Deleted R138 (10k) Added

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LOCATION AND FUNCTION OF CONTROLS

BASE UNIT

!§

!¶

!•

!ª

@º

@¡

@™

SECTION 1

GENERAL

!∞

!¢

HANDSET

1 LINE 1 lamp 2 LINE 1/FLASH button 3 MUTE button 4 LINE 2 lamp 5 LINE 2/FLASH button 6 INTERCOM button 7 OFF button 8 VOLUME – button 9 L1 RINGER ON/OFF button !º L2 RINGER ON/OFF button !¡ VOLUME + button

!¡

!º

!™ INTERCOM lamp !£ Speaker !¢ Antenna !∞ MUTE lamp !§ POWER lamp !¶ CHARGE lamp !• SPARE BATTERY lamp !ª DIAL MODE (PULSE/TONE) @º HOLD button @¡ CONF button @™ OPEN c (Spare Battery) knob

!£

!™

!∞

!¢

!£ !™

!¡

!º

1 Speaker 2 VOL (Volume) +/– switch 3 LINE 1/FLASH button 4 Dialing keys 5 HOLD/PAUSE button 6 SPEED DIAL/PGM button 7 CONF/CLEAR button 8 Microphone 9 INTERCOM/DEL button !º REDIAL button !¡ CALLER ID button !™ OFF button !£ LINE 2/FLASH button !¢ LCD panel !∞ Antenna

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This section is extracted from instruction manual.

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– 9 –

– 10 –

SECTION 2

)

DISASSEMBLY

Note : Follow the disassembly procedure in the numerical order given.

2-1. BATTERY PACK REMOVAL

Lid, Battery pack

Battery pack (BP-T23)

2-2. HAND CABINET (REAR) REMOVAL

Screws

(+BTP 3x12)

Hand cabinet (Rear)

Hand cabinet (Front

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)

2-3. ANTENNA REMOVAL

Tube

Antenna (ANT1)

Hand cabinet (Front)

2-4. HAND MAIN BOARD REMOVAL

Screw (+P 3x8)

Hand main board

Screws

(+BTP 2x6)

Screw (+BTP 3x12)

Holder, Antenna

Screw (+BTP 3x12)

Screws (+P 2x8)

Switch, Rubber key (VOL)

Hand main cabinet (Front

– 12 –

SECTION 3

CIRCUIT OPERATION

RF SECTION OVERVIEW

1.0 Introduction

The basic function of the base and handset RF sections is to provide a full duplex wireless link between the handset and base sections of the telephone. This is accomplished by setting up two simultaneous communications links between the handset and base sections. The RF receiver and transmitter circuity essentially provide a link between the microphone and speaker in the handset to the telephone line in base set. In this way the phone performs exactly as a corded phone, except without the cord.

The frequency at which the handset transmits to the base is centered around 926.55MHz, and the frequency at which the base transmits to the handset is centered around 903.8MHz. Unlike a normal 46/49MHz cordless phone, which directly modulates audio (voice) onto the RF carrier, a phone using the Mark 3 module first digtizes the audio signal and then modulates high speed data onto the RF car rier . The data rate which is modulated onto the RF carrier is 48kbps. On the receiver side the data is extracted and then converted back into the original audio signal.

It is important to note that the synthesizer/prescaler IC only operates up to 500MHz. The VCO's therefor e oscillate at roughly 450MHz. The 900MHz signals needed for the transmit and receive sections are generated from the second harmonic of the VCO frequencies.

The following section will outline the transmit frequencies used as well as the corresponding LO frequency which is used for the receiver. This is followed by the Block diagram and a block by block functional description of the modules.

1.1 Frequency Tables

This section outline the RF frequencies and corresponding channel numbers. The handset uses a high side LO while the base uses a low side LO to down-convert the incoming signal.

1.1.1 Handset

Channel Transmit (MHz) Receive (MHz) RX LO (MHz)

1.1.2 Base Unit

Channel Transmit (MHz) Receive (MHz) RX LO (MHz)

1 925.05 902.3 913.0 2 925.35 902.6 913.3 3 925.65 902.9 913.6 4 925.95 903.2 913.9 5 926.25 903.5 914.2 6 926.55 903.8 914.5 7 926.85 904.1 914.8 8 927.15 904.4 915.1 9 927.45 904.7 915.4

10 927.75 905.0 915.7

1 902.3 925.05 914.35 2 902.6 925.35 914.65 3 902.9 925.65 914.95 4 903.2 925.95 915.25 5 903.5 926.25 915.55 6 903.8 926.55 915.85 7 904.1 926.85 916.15 8 904.4 927.15 916.45 9 904.7 927.45 916.75

10 905.0 927.75 917.05

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1.2 Block diagram

Both the handset and base RF sections follow the same block diagram shown below with only minor changes to incorporate the different transmit and receive frequencies.

2 POLE CERAMIC

Ist RX AMP SAW FILTER 2nd RX AMP MIXER 10.7MHz CERAMIC IF AMP

V-Tune

LOW PASS

FILTER

TX OP AMP

TX DATA

Fin

V-Tune

DUAL PRESCALER SYNTHESIZER

10.7MHz CERAMIC

MC10156

DEMODULATOR

RX LO

4.57MHz

3.2MHz REFERENCE

3 LINE DATA BUS

DATA O/

Figure 1. RF Section Block Diagram

As can be seen by the block diagram, there are several important input/output signals which are necessary for operation of the RF section (this does not include the separate supply lines for both TX and RX sections). An 18.25MHz reference is present for use in the frequency synthesizers. The accuracy of this 18.25 MHz input will affect the transmit and recei ve frequencies. In order to ensure proper operation of the RF sections, the 18.25 MHz reference signal must be at least 500mV in amplitude. Also present is the 3-line serial data bus on whic h data is transferred to the synthesizers to set both the transmit and receive frequencies.

The modulation input allows digital data to be modulated directly onto the TX carrier. The Data output is the demodulated signal after being filtered and shaped by a comparator. The data is then sent to the AMD ASIC where the original voice signal is reconstructed.

The RF section performs a single down-conversion of the incoming RF signal to 10.7MHz where it is demodulated and sent to the AMD ASIC. The transmit section directly modulates the carrier.

The following section explains the individual blocks in the RF section in detail. All reference to part numbers correspond to the handset schematic

RF SECTION DETAILED OPERATION

2-1. Antenna Section

2.1.1 Antenna The antenna is a device which allows ef fecti v e conversion of energy from air to the RF circuitry. The antennas used are a retractable 1/2 wave with 2.5dB gain relative to an isotropic radiator and a fixed 1/4 wave antenna with roughly 0dB gain relative to an isotropic radiator. T he duplex er and f ilters w hich follo w the antenna, require a 50Ω match to operate properly . T he antenna is not matched to 50Ω and requires a simple microstrip matching network to achieve this. If a network analyzer is attached to the BFA connector after disconnecting the duplexer , the antenna match may be measured. In order to achieve a good 50Ω match, one must be careful not to obstruct the antenna as any object near the antenna will affect its impedance

2.1.2 Duplexer The Duplexer ensures that the two bandpass filters do not interact with each other. It accomplishes this by making each filter see a high impedance from the opposite filter in its own passband. This is necessary to ensure that both filter work effectively when connected together. If the Duplexer were not present, mismatches from one filter would cause the passband of the other to be distorted and this would degrade performance.

The Duplexer itself is simply composed of two microstrip and discrete filters which shift each filters out of band match to a high impedance. To ensur e that the Duplexer is operating correctly, the match looking into the filters from the BFA connector may be measured. To do this it is necessary to remo v e the 0Ω resistor which connects the antenna to the Duplexer. A return loss of approximately 15dB should be measured for both the TX and RX bands.

2.1.3 RX, TX Bandpass Filters The RX and TX bandpass filters provide two functions. The first is to effectively pass the correct frequencies to the RX and TX sections. It is important especially for the RX section that these filters have a low insertion loss in order to ensure a low front end noise figure. These filters are also designed to provide > 25dB rejection for the opposite band. This means that the transmit carrier will be attenuated by at least 25dB before entering the receive section of the phone. A plot of the low band filter is shown in Figure 2, 3 below.

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0dB

10dB/div

902-905MHz Passband

815

925-928MHz Reject Band

1015

Figure 2. Low band Ceramic filter response

For this filter the insertion loss is less than 3dB at 902 to 905MHz while the 925 – 928MHz band has > 25dB attenuation. This f ilter is used for the RX filter in the handset or the TX filter in the base. The high band filter characteristic is shown below. This filter is used for the handset TX filter and base RX filter.

925-928MHz Passband

0dB

10dB/div

815

902-905MHz Reject Band

Figure 3. High band Ceramic filter response

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1015

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