Akai CFT2716 User manual

CFT2716
Safety Instructions
Features & Specifications
Block Diagram
Circuit Diagram
Disassembly
Pin Descriptions
Exploded View Diagram
Spare Part List
Model:
SERVICE MANUAL
This manual is the latest at the time of printing, and does not
include the modification which may be made after the printing,
by the constant improvement of product.

IMPORTANT SERVICE SAFETY INFORMATION
Operating the receiver outside of its cabinet or with its back removed involves a shock hazard.
Work on these models should only be performed by those who are thoroughly familiar with precautions
necessary when working on high voltage equipment.
Exercise care when servicing this chassis with power applied. Many B plus and high voltage RF
terminals are exposed which, if carelessly contacted, can cause serious shock or result in damage to the
chassis. Maintain interconnecting ground lead connections between chassis, escutcheon, picture tube dag
and tuner when operating chassis.
These receivers have a “polarized” AC line cord. The AC plug is designed to fit into standard AC
outlets in one direction only. The wide blade connects to the “ground side” and the narrow blade
connects to the hot “side” of the AC line. This assures that the TV receiver is properly grounded to the
house wiring. If an extension cord must be used, make sure it is of the “polarized” type.
Since the chassis of this receive is connected to one side of the AC supply during operation,
service should not be attempted by anyone not familiar with the precautions necessary when working on
these types of equipment.
When it is necessary to make measurements or tests with AC power applied to the receiver chassis,
an Isolation Transformer must be used as a safety precaution and to prevent possible damage to
transistors. The Isolation Transformer should be connected between the TV line cord plug and the AC
power outlet.
Certain High voltage (HV) maybe cause X-ray radiation. Receivers should not be operated with
HV levels exceeding the specified rating for their chassis type. Higher voltage may also increase the
possibility of failure in the HV supply.
It is important to maintain specified values of all components in the horizontal and high voltage
circuits and anywhere else in the receive that could cause a rise in high voltage, or operating supply
voltages. No changes should be made the original design of the receiver.
Components shown in the shaded areas on the schematic diagram and/or identified by in the
replacement parts list should be replaced only with exact factory recommended replacement parts. The
use of unauthorized substitute parts man creats may create shock, fire, X-ray radiation, or other hazards.
To determine the presence of high voltage, use an accurate high impedance HV meter connected
between the second anode lead and he CRT dag grounding device. When servicing the High Voltage
System remove static charges from it by connecting a 10K Ohm resistor in series Wan insulated
wire(such as test probe) between the picture tube dag and 2nd anode lead(Have AC line cord
disconnected fromAC supply).
The picture tube use in this receiver employ integral implosion protection. Replace with a tube of
the same type number for continued safety. Do not lift picture tube by the neck. Handle the picture tube
only when wearing shatterproof goggles and after discharging the high voltage completely, Keep others
without shatter proof goggles away.
Before returning the receiver to the user, perform the following safety checks:
1. Inspect all lead dress to make certain that leads are not pinched or that hardware is not lodged
between the chassis and other metal parts in the receiver.
2. Replace all protective devices such as non-metallic control knobs, insulating fishpapers, cabinet
backs, adjustment and compartment covers of shiedls, isolation resistor-capacitor networks,
mechanicalinsulatorsetc.

3. To be sure that not shock hazard exists, a check for the presence of leakage current should be
made at each exposed metal part having a return path to the chassis (antenna, cabinet metal,
screw heads knobs and/or shafts, escutcheon, etc.) in the following manner.
Plug the AC line cord directly into a 120V, AC receptacle. (Do not use an Isolation Transformer
during these checks.) All checks must be repeated with the AC line cord plug connection reversed. (If
necessary, a nonpolarized adapter plug must be used only for the purpose of completing these checks.)
If available, measure current using an accurate leakage current tester. Any reading of 0.35mA or
more is excessive and indicates a potential shock hazard which must be corrected before returning the
receiver to owner.
If a reliable leakage current tester is not available, this allernate method of measurement should be
used. Using two clip leads, connect a 1500 Ohm, 10 watt resistor paralleled by a 0.15uF capacitor in
series with a known earth ground, such as a water pipe or conduit and the metal part to be checked. Use
a VTVM or VOM with 1000 Ohms per Volt, or higher, sensitivity to measure this AC voltage drop
across the resistor,. Any reading of 0.35 volt RMS of more is excessive and indicates potential shock
hazard which must be corrected before returning he receiver to the owner.
ALIGNMENT PROCEDURES
PLEASE READ BEFORE ATTEMPTING SERVICE
1. Use an Isolation Transformer when performing any service on this chassis.
2. Never disconnect any leads while receiver is in operation.
3. Disconnect all power before attempting an repairs.
4. Do not short any porsition of the circuit while the power is on.
5. For safety reasons, replacing any components should be according with identical replacement
parts (SEE PARTS LIST).
6. Before testing, warm up the TV for at least 30 minutes and demagnetize the CRT with an
external degaussing coil.
7. When removing a PCB or related component, after unfastening or changing a wire, be sure to
put the wire back in its original position.
8. Inferior silicon grease can damage IC’s and transistors. When replacing IC’s and transistors, use
only specified silicon grease,. Remove all old silicon when applying new silicon.
9. Before removing the anode cap, discharge eiecticity because it contains high voltage.

FUNCTION AND SPECIFICATION
TUBE/POWER SUPPLY
TUBE TYPE PF
SIZE 27''
ASPECT RATIO 4∶3
POWER SUPPLY ~120V，60Hz
MAIN POWER SWITCH
SOFT
SWITCH
TUNER
BUILT-IN FS TUNER YES
# OF CHANNEL/PROGRAM 181 CH
COLOR SYSTEM NTSC
SOUND SYSTEM M
AV NTSC 3.58/4.43 AV NTSC 3.58
PICTURE
COMB FILTER 2LINE
TINT, COLOR, BRIGHTNESS, CONTRAST AND SHARPNESS CONTROL YES
USER SELECTABLE PICTURE CONTROL(NORMAL,BRIGHT,USER,SOFT) YES
USER SELECTABLE 3-STAGE COLOR TEMPERATURE CONTROLS YES
OSD LANGUAGE ENG，FR，SPA
SOUND
STEREO/MONO MTS/SAP
AV STEREO YES
SURROUND YES
TONE CONTROL(BASS/TREBLE/BALANCE) YES
USER SELECTABLE SOUND CONTROL YES
SPEAKER QUANTITY 2
AUDIO OUTPUT POWER 3W×2
USER CONVENIENCE
FULL FUNCTION REMOTE CONTROL YES
CCD YES
V-CHIP YES
CHILD LOCK YES
SLEEP TIMER YES
RECALL YES
QUICK VIEW YES
CONNECTORS
CABLE/ANTENNA INPUT 1 REAR
AV INPUT 2 REAR,1SIDE
S-VIDEO INPUT 1 REAR
COMPONENT VIDEO INPUT (YCbCr) 1 REAR
AV OUTPUT 1 REAR(Audio)
HEADPHONE OUTPUT NO

Block diagram
TUNER
NTSC M/N
UOC
TDA9378
AUDIO POWER
TDA2616
RGB
OUT
H OUT
V OUT
TDA8177F
TRAP VEDIO SWITCH
TC4052
VO V1 V2 Y/C
VEDIO terminal
COMB FILER
TDA9183
CRT
MTS/SAP
TDA9850
AUDIO terminal
R/L1 R/L2 R/LO
AUDIO PRO
TDA9859
SAW
5V -12V 12V 18V 45V 135V
TDA16846

1995 Jun 19 6
Philips Semiconductors Preliminary specification
I2C-bus controlled BTSC stereo/SAP decoder TDA9850
PINNING
SYMBOL PIN DESCRIPTION
VEO 1 variable emphasis output for dbx
VEI 2 variable emphasis input for dbx
CNR 3 capacitor noise reduction for dbx
CM4 capacitor mute for SAP
CDEC 5 capacitor DC-decoupling for SAP
AGND 6 analog ground
DGND 7 digital ground
SDA 8 serial data input/output
SCL 9 serial clock input
VCC 10 supply voltage (+9 V)
COMP 11 composite input signal
VCAP 12 capacitor for electronic filtering of supply
CP1 13 capacitor for pilot detector
CP2 14 capacitor for pilot detector
CPH 15 capacitor for phase detector
CADJ 16 capacitor for filter adjustment
CER 17 ceramic resonator
CMO 18 capacitor DC-decoupling mono
CSS 19 capacitor DC-decoupling stereo/SAP
CR20 adjustment capacitor, right channel
OUTR 21 output, right channel
CSDE 22 capacitor SAP de-emphasis
SAP 23 SAP output
Vref 24 reference voltage 0.5 ×(VCC −1.5 V)
CL25 adjustment capacitor, left channel
CND 26 noise detector capacitor
OUTL 27 output, left channel
MAD 28 programmable address bit
CTW 29 capacitor timing wideband for dbx
CTS 30 capacitor timing spectral for dbx
CW31 capacitor wideband for dbx
CS32 capacitor spectral for dbx Fig.2 Pin configuration.
f
page
TDA9850
MHA012
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
VEO CS
CW
CTS
CTW
CND
CSDE
CL
CR
CSS
CMO
Vref
VEI
CNR
CM
CDEC
AGND OUTL
SAP
OUTR
CER
MAD
DGND
SDA
SCL
VCC
COMP
VCAP
CP1
CP2
CPH
CADJ

Service Flow Chart
Power supply
Check input voltage
Check voltage of C911+(12V)
Check voltage of C919+(5V)
Check voltage of C155+(3.3V)
Check RY901 turn on
Check voltage of C929+(135V)
Check voltage of C945+(48V)
Check voltage of C939+(12V)
Check voltage of C946+(-12V)
Check voltage of C994+(9V)
Check voltage of C933+(8V)
Check voltage of C930+(5V)

CPU circuit
Check voltage of N103 pin54,pin56,pin61(3.3V)
Check waveform of N103 pin58,pin59
Check waveform of N103 pin2,pin3
Check voltage of N602 pin8 (5V)
Check waveform of N602 pin5,pin6
Vertical circuit
Check voltage of N103 pin14,pin39(8V)
Check waveform of N103 pin26
Check waveform of N103 pin21,pin22
Check voltage of N401 pin3(48V)
Check voltage of N401 pin2(12V)
Check voltage of N401 pin4(-12V)
Check waveform of N401 pin1,pin7
Check waveform of N401 pin5

Horizontal circuit
Check voltage of N103 pin14,pin39(8V)
Check waveform of N103 pin33
Check voltage of C945+(48V)
Check waveform of V401-B
Check waveform of V401-C
Check voltage of C929+(135V)
Check waveform of V402-B
Check waveform of V402-C
Check voltage of C415+(200V)

Video circuit
Check voltage of C109+(33V)
Check voltage of C106+(5V)
Check waveform of tuner pin4,pin5
Check waveform of tuner pin11(IF)
Check voltage of L103 and L104(8V)
Check waveform of N103 pin23,pin24
Check waveform of N103 pin38
Check waveform of N103 pin40
Check waveform of N802 pin12, pin13
Check waveform of N302 pin12, pin14, pin16
Check waveform of N103 pin42, pin43
Check waveform of N103 pin51,pin52,pin53
Check video amplify circuit

Audio circuit
Check waveform of N103 pin28
Check waveform of N103 pin44
Check waveform of N201 pin11
Check voltage of N201 pin10(9V)
Check waveform of N201 pin8, pin9
Check waveform of N201 pin21, pin27
Check waveform of N801 pin3,pin5
Check voltage of N801 pin6(8V)
Check waveform of N801 pin16,pin17
Check waveform of N801 pin15,pin18
Check waveform of N202 pin1,pin9
Check voltage of N202 pin7
Check waveform of N202 pin4,pin6
Check waveform of speaker

TEST EQUIPMENT
1. Standard Signal Generator (PT5820)
2. Oscilloscope
3. Digital Voltmeter
4. High Voltage Meter(40KV)
5. Demagnetizing Coil
Tip: some adjustments must be performed in the SERVICE menu. You can enter the SERVICE
menu in the following way:
1. Press the MENU button on the remote control then press the INFO button on the remote control
at least 5 times immediately.
2. Press the CH+/- buttons to select the desired mode or press 0-9 number buttons to enter the
SERVICE “X” menu directly and then press the CH+/- buttons to select the desired mode.
3. Press the VOL+/- buttons to change the settings.
IFADJUSTMENT
1.Enter the SERVICE menu and press the number button “4” on the remote control to bring up
SERVICE 4.
2.Set the IFFS to “1”.
B+ ADJUSTMENT
TEST EQUIPMENT: DIGITAL METER
1.Operate the TV set with AC 120V.
2.Connect the digital voltmeter + lead to C929 and GND. Adjust the RP901 until the meter
reading DC135±0.5V.
GEOMETRY ADJUSMENT
1.Receive a geometry pattern.
2.Enter the SERVICE menu (SERVICE 1 for horizontal and SERVICE 2 for vertical).
3.Select a value between 0 and 63, and the changed value is stored immediately.
Horizontal:
6PAR: Horizontal Parallelogram
Set the horizontal parallelogram to change to rectangle or trapezium.
6BOW: Horizontal Bow
Set the vertical lines straight.
6HSH: Horizontal Delay (horizontal shift)
Set the horizontal centre of the picture at the centreofthetube.