SERVICE MANUAL
PUBLISHED IN JAPAN, Jan., 2001
FILE NO. 2B0-200012
FT-7800A
CORDLESS TELEPHONE
-- 1 --
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
in the schematic diagram and the parts list. Before replacing
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.
-- 2 --
OPERATING CONTROLS
BASE UNIT CONTROLS
HANDSET CONTROLS
-- 3 --
Alignment Point Location on Base Main PCB and Base RF PCB
Power
Meter
Frequency
Counter
Deviation
Meter
RF
Test Point
RF
Test Point
J1
TEL Line
Jack
1kHz 77.5mV
AC
Adapter
AC 120V
60Hz
J2
DC IN
9V Jack
BASE Unit
AF GEN.
J1
TEL LINE Jack
J2
DC IN 9V Jack
RT3
RT4
CT1
RF
TEST POINT
RF PCB
ALIGNMENT PROCEDURE
Base Unit
Transmitter Section
Connections
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
RT3
(TX Power)
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.
2
CT1
(TX Frequency)
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.
3
RT4
(TX Modulation)
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.
-- 4 --
J1
TEL LINE Jack
J2
DC IN 9V Jack
RT1
RT2
L9
RF
TEST POINT
AF
TEST POINT
Alignment Point Location on Base Main PCB and Base RF PCB
RF SG
J1
TEL Line
Jack
BASE Unit
AC Adapter
AC 120V
60Hz
-
+
Dummy Load
(600-ohm)
AC Voltmeter
AF Terminal
DC Voltmeter
J2
DC IN9V Jack
-
+
RF
Test Point
Base Unit
Connections
Alignment Procedure
Step
Preset to
Adjustment
Remarks
1
SG: 1mV
No modulation
L9
(Discriminator
Voltage)
Press the "PAGE" key 3 times to enter the TEST Mode 4. Connect the
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.
2
SG: 1 mV
1 kHz
±20 kHz
Deviation
RT2
(RX AF
Voltage)
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.
3
SG: +2.0 dB
µV
1 kHz
±20 kHz
Deviation
RT1
(SQ Point)
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.
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.