Toshiba FT 7800A Service Manual
FILE NO. 2B0-200012
SERVICE MANUAL
CORDLESS TELEPHONE
FT-7800A
PUBLISHED IN JAPAN, Jan., 2001
CONTENTS
SAFETY PRECAUTIONS ...................................................................................................................... 1
OPERATING CONTROLS.....................................................................................................................2
ALIGNMENT PROCEDURE .................................................................................................................. 3
BLOCK DIAGRAMS...............................................................................................................................7
SCHEMATIC DIAGRAMS......................................................................................................................9
TROUBLESHOOTING HINTS ............................................................................................................. 13
IC AND TRANSISTOR VOLTAGE CHART .........................................................................................20
SEMICONDUCTOR LEAD IDENTIFICATION.....................................................................................24
ELECTRICAL PARTS LOCATION ...................................................................................................... 26
WIRING DIAGRAMS............................................................................................................................ 30
EXPLODED VIEW AND MECHANICAL PARTS LIST ........................................................................32
PARTS LIST......................................................................................................................................... 36
ASSEMBLY PARTS LIST .................................................................................................................... 49
SPECIFICATIONS ............................................................................................................................... 50
SAFETY PRECAUTIONS
Before returning any models to the customer, a safety check of the entire instrument should be made.
The service technician must be sure that no protective device built into the instrument by the manufacturer
has become defective or inadvertently degraded during servicing.
1. WARNING:
Alterations of the design or circuitry of these models should not be made.
Any design changes or additions such as, but not limited to, circuit modifications, auxiliary speaker
jacks, switches, grounding, active or passive circuitry, etc. may alter the safety characteristics of these
models and potentially create a hazardous situation for the user.
Any design alterations or additions will void the manufacturer’s warranty and will further relieve the
manufacturer of responsibility for personal injury or property damage resulting therefrom.
2. PRODUCT SAFETY NOTICE
Many electrical and mechanical parts in this chassis have special characteristics. These characteristics
often pass unnoticed and the protection afforded by them cannot necessarily be obtained by using
replacement components rated for higher voltage, wattage, etc. Replacement parts that have these
special safety characteristics are identified in this manual and its supplements; electrical components
having such features are identified by a
any of these components, read the parts list in this manual carefully. The use of substitute replacement
parts that do not have the same safety characteristics as specified in the parts list may create shock, fire
or other hazards.
in the schematic diagram and the parts list. Before replacing
— 1 —
HANDSET CONTROLS
OPERATING CONTROLS
BASE UNIT CONTROLS
— 2 —
T
Base Unit
Transmitter Section
Connections
ALIGNMENT PROCEDURE
Power
Meter
Frequency
Counter
Deviation
Meter
RF
Test Point
RF
Test Point
BASE Unit
J2
DC IN
9V Jack
J1
TEL Line
Jack
1kHz 77.5mV
AF GEN.
AC
Adapter
AC 120V
60Hz
Preset
a) Connect the AC adapter to the base unit while pressing the “PAGE” key, and keep pressing it continuously for
approximate 2 seconds.
b) Release the “PAGE” key when entering TEST mode 1 with IN USE LED lighting.
Alignment Procedure
Step Adjustment Remarks
1
2
3
RT3
(TX Power)
CT1
(TX Frequency)
RT4
(TX Modulat ion)
Connect the Power Meter to the RF test point on the Base MAIN PCB. Adjust
RT3 for a −6.0 dBm reading on the Power Meter.
Connect the Frequency Counter to the RF test point on the Base MAIN PCB.
Adjust CT1 to make sure that the frequency is 925.908974 MHz.
Press the “PAGE” key to enter the TEST Mode 2. Connect the AF Generator to
the TEL Line Jack on the Base Main PCB. Make sure that the output is 1 kHz
77.5 mV from the AF Generator.
Connect the Deviation Meter to the RF test point on the Base MAIN PCB.
Adjust RT4 to indicate ±20 kHz Dev.
Alignment Point Location on Base Main PCB and Base RF PCB
RF PCB
CT1
RT4
— 3 —
RT3
J1
TEL LINE Jack
J2
DC IN 9V Jack
RF
TEST POIN
T
Base Unit
Connections
AC Voltmeter
AC 120V
60Hz
RF SG
AC Adapter
−
RF
Test Point
+
DC IN 9V Jack
J2
BASE Unit
J1
TEL Line
Jack
AF Terminal
Dummy Load
(600-ohm)
−
+
DC Voltmeter
Preset
a) Connect the AC adapter to the base unit while pressing the “PAGE” key, and keep pressing it continuously for
approximate 2 seconds.
b) Release the “PAGE” key when entering TEST mode 1 with IN USE LED lighting.
Alignment Procedure
Step Preset to Adjustment Remarks
Press the “PAGE” key 3 times to enter the TEST Mode 4. Connect the
1
SG: 1mV
No modulation
L9
(Discriminator
Voltage)
RF Signal Generator to the RF test point on the Base MAIN PCB. Make
sure that the frequency is 903.337954 MHz.
Connect the DC Voltmeter to the AF test point. Adjust L9 to indicate DC
1.4 V.
SG: 1 mV
2
1 kHz ±20 kHz
Deviation
SG: +2.0 dBµV
3
1 kHz ± 20 kHz
Deviation
RT2
(RX AF
Voltage)
RT1
(SQ Point)
Connect the AC Voltmeter across a 600-ohm dummy to the Telephone
Line Jack. Adjust RT2 for a 173 mV reading on the AC voltmeter.
Press the “PAGE” key to enter the TEST Mode 5. Make sure that the
frequency of RF SG output is 903.337954 MHz. Adjust RT1 to turn to
the point where the CHG LED just turns on.
Alignment Point Location on Base Main PCB and Base RF PCB
L9
RT2
RT1
J1
TEL LINE Jack
J2
DC IN 9V Jack
RF
TEST POIN
AF
TEST POINT
— 4 —
Handset Unit
Transmitter Section
Connections
Power
Meter
Frequency
Counter
Deviation
Meter
RF
Test Point
RF
Test Point
HANDSET Unit
J601
Battery
Connector
MIC + Pin
AF GEN.
1kHz 9mV
DC Power Supply
DC 3.8V
Preset
a) Connect DC power supply to battery connector on the handset unit.
b) Turn the DC power supply ON while pressing “ ” and “#” keys, and keep pressing the keys continuously for
approximate 2 seconds.
c) Release keys when entering TEST mode 1 with TALK LED lighting and beep.
Alignment Procedure
Step Adjustment Remarks
1
2
3
RT604
(TX Power)
CT601
(TX Frequency)
RT603
(TX Modulat ion)
Connect the RF power Meter to the RF test point on the handset MAIN PCB.
Adjust RT604 for a −5.0 dBm reading on the Power Meter.
Connect the Frequency Counter to the RF test point on the handset MAIN
PCB. Adjust CT 601 to make sure that the frequency is 903.636249 MHz.
Press the “2” key to enter the TEST Mode 2. Connect the AF Generator to
the MIC Connector. Make sure that the output is 1 kHz 9 mV from the AF
Generator.
Connect the Deviation Meter to the RF test point on the handset MAIN PCB.
Adjust RT603 to indicate ±20kHz Dev.
Alignment Point Location on Handset Main PCB and Handset RF PCB
RT603
CT601
RF PCB
— 5 —
RT604
RF
TEST POINT
Handset Unit
Connections
RF SG
DC Power Supply
−
RF
Test Point
+
Battery Connector
DC 3.8V
J601
HANDSET Unit
Connector
AF Terminal
SP
Dummy Load
(150-ohm)
−
+
DC Voltmeter
AC Voltmeter
Preset
a) Connect DC power supply to battery connector on the handset unit.
b) Turn the DC power supply ON while pressing “ ” and “#” keys, and keep pressing the keys continuously for
approximate 2 seconds.
c) Release keys when entering TEST mode 1 with TALK LED lighting and beep.
Alignment Procedure
Step Preset to Adjustment Remarks
Press the “4” key to enter the TEST Mode 4 . Connect the RF Signal
1
No modulation
2
1 kHz ±20 kHz
SG: −1.0 dBµV
3
1 kHz ±20 kHz
SG: 1 mV
SG: 1 mV
Deviation
Deviation
CT602
(Discriminator
Voltage)
RT602
(RX AF
Output)
RT601
(SQ Point)
Generator to the RF test po int on th e ha nd set MA IN P CB. M ake su re
that the frequency is 926.207269 MHz.
Connect the DC Voltmeter to the AF test point. Adjust CT602 to
indicate DC 1.4 0 V.
Connect the RF Signa l Generat or to the RF test po int on the ha ndset
MAIN PCB. Make sure that the frequency is 926.207269 MHz.
Connect the AC Voltmeter a cross a 1 50 -ohm dummy to the SP
Connector. Adjust RT 602 for a 35.5 mV reading on the AC
Voltmeter.
Press the “5” key to enter the TEST Mode 5. Make sure that the
frequency of RF SG output is 926.207269 MHz. Adjust RT601 to
turn to the point where Ringer rings.
Alignment Point Location on Handset Main PCB and Handset RF PCB
AF
TEST POINT
CT602
RT602
RT601
RF PCB
— 6 —
RF
TEST POINT
Base Unit
BLOCK DIAGRAMS
— 7 —
Handset
— 8 —
Base Unit
SCHEMATIC DIAGRAMS
— 9 — — 10 —
Handset
— 11 — — 12 —
1. The bell does not ring.
TROUBLESHOOTING
When the PAGE SW of the
base is pressed, does the
ringer on the handset ring?
OK
When the TEL SG is joined
with the base to make bell
signal, is there pulse wave
at Pin 4 of IC4?
OK
Is there pulse wave at
pin 21 of IC2?
OK
Check IC2 and its
peripheral circuit.
NG
NG
NG
See 2. The bell does not
ring & page does not ring.
Check IC4 and TEL network
circuit.
Check C90, R40 and R62.
If you want to reset the unit to the factory settings
HANDSET
1)Connect the battery with pressing and buttons, and keep pressing the buttons continuously for
approximate 2 seconds.
2) Release buttons when entering TEST mode with beep.
3) Press
MEM
button.
4) Disconnect the battery.
BASE UNIT
1) Press and hold the "PAGE" key about 2 seconds while turning the power on.
The IN USE LED will flash one time.
2) Disconnect the AC ADAPTOR.
— 13 —
2. The bell does not ring & page does not ring.
Can the base and handset
be connected?
OK
Press handset DIAL key
while in TALK MODE.
Can key touch sound be
heard from the ringer?
OK
When the PAGE SW S1 of
the base is pressed, does
pin20 of IC2 change from
high to low?
NG
NG
NG
See 3. The base and
handset cannot be
connected.
When the key of the
handset is pressed, can the
pulse output at pin 38 of
IC602 be seen?
OK
At the Q613 collector, can
the pulse wave be seen?
OK
Check RINGER Y601.
Check R67, R104 and S1.
NG
NG
Check IC602.
Check R694, R695 and
D610.
OK
Check IC2 and its
peripheral circuit.
— 14 —
3. The base and handset cannot be connected.
Check whether the base
can be set in the test
mode 1.
OK
Check the TX POWER and
the TX FREQUENCY on
the base unit.
OK
Press the "PAGE" key
2 times, check whether
deviation of the TX data is
app. ±35 kHz Dev.
OK
Press the "PAGE" key
5 times, and apply
903.337954 MHz
(250 Hz ±35 kHz Dev.)
1 mV output signal from
RF jack. Can the INUSE
LED be lighted?
OK
NG
NG
NG
NG
Check IC2 and its
peripheral circuit.
Check base RF unit (B350).
Check whether there is a
250 Hz data waveform at
MOD of RF unit.
OK
Check base RF unit (B350).
Check whether there is a
250 Hz data waveform at
pin 28 of IC1.
OK
Check whether there is a
250 Hz data waveform at
Pin 24 of IC1.
NG
NG
NG
Check RT4, C107, R79,
R80, R81, R82 and R83.
Check base RF unit and the
peripheral circuit of IC1.
Check R14, C25, C26,
R119 and their peripheral
circuits.
Check whether the
handset can be set in the
test mode 1.
OK
Check the TX POWER and
the TX FREQUENCY on
the handset unit.
OK
NG
NG
OK
Check whether there is a
250 Hz data waveform at
pin 38 of IC2.
OK
Check IC2 and its
peripheral circuit.
Check IC602 and its
peripheral circuit.
Check handset RF unit
(B850).
NG
Check R36, R89 and
their peripheral circuits.
— 15 —
Press the "3" key, check
whether deviation of the
TX data is app. ±35 kHz Dev.
NG
Check whether there is a
250Hz data waveform at
C717.
NG
Check RT603, R626, R672,
R673, R679, R680 and
C642.
OK
Press the "6" key, and apply
926.207269 MHz
(250 Hz ±35 kHz Dev.) 1mV
output signal from RF jack.
Check whether the bell ring.
OK
Place the handset on the
base to charge about
5 seconds, then connect
again.
NG
OK
Check handset RF unit
(B850).
Check whether the 250 Hz
data wareform from pin 28
of IC601.
OK
Check whether there is a
250 Hz data waveform at
pin 24 of IC601.
OK
Check whether there is a
250 Hz data waveform at
pin 40 of IC602.
OK
NG
NG
NG
Check handset RF unit and
the peripheral circuit of
IC601.
Check R614, R703, C631,
C632 and their peripheral
circuits.
Check R616, R663 and
their peripheral circuits.
Check IC602 and its
peripheral circuit.
— 16 —
4. Cannot make a phone call (pulse).
Preset: Press "FLASH" key for about 2 seconds, then press "#" key to enter "Pulse" mode.
Can the base and handset
be connected?
OK
While in TALK MODE,
press number key of the
handset.
Check whether square
waveform from pin 13 of
IC2 is fed.
OK
Check Q16, RL1 and their
peripheral circuits.
NG
NG
See 3. The base and
handset cannot be
connected.
Check IC2.
5. Cannot make a phone call (tone).
Preset: Press "FLASH" key for 2 seconds, then press "”" key to enter "Tone" mode.
Can the base and handset
be connected?
OK
While in TALK MODE,
press dial key of the
handset. Can tone
waveform from pin 1of IC2
is fed?
OK
Can tone signal be heard
from the handset speaker?
OK
Check the base TEL-line
circuit and RELAY control
circuit.
NG
NG
NG
See 3. The base and
handset be cannot be
connected.
Check IC2.
Check IC1, Q3 and their
peripheral circuits.
— 17 —
Loading...