Casio EV-2500B Troubleshooting guide

R
(with price)
EV-2500B(KX-618)
MAY. 1995
INDEX

— 1 —
CONTENTS
SPECIFICATIONS ......................................................................................... 2
BLOCK DIAGRAM ........................................................................................ 3
CIRCUIT DESCRIPTION ............................................................................... 4
DISASSEMBLY ............................................................................................. 5
DIAL STRINGING DIAGRAM........................................................................ 6
ADJUSTMENT............................................................................................... 7
TROUBLESHOOTING................................................................................. 12
PRINTED CIRCUIT BOARDS ..................................................................... 13
EXPLODED VIEW ....................................................................................... 15
ELECTRICAL PARTS LIST......................................................................... 16
MECHANICAL PARTS LIST ....................................................................... 23
IC AND TRANSISTOR LEAD IDENTIFICATION ........................................ 25
SCHEMATIC DIAGRAMS ........................................................................... 27
WAVEFORMS.............................................................................................. 29

— 2 —
SPECIFICATIONS
Item Specification
1. Reception channels TV— VHF: 2 ~ 13 ch UHF: 14 ~ 69 ch
RADIO— FM: 88~108 MHz AM: 530~1710 KHz
2. Power voltage DC 6.0 V
3. Power consumption Approx. 3.5 W
4. Current consumption Approx. 580 mA
5. Battery life (with alkaline batteries) Approx. 11 hours
Batteries : 3 D size batteries
6. Power supply Car adaptor : CA-K65
AC adaptor : AD-K65, 64
Earphone jack : 3.5ø mini
7. Connection terminals External power jack : 6.0 V DC IN
External antennea jack : 3.5ø mini
Audio / Video jack : 3.5ø
8. Screen size 2.5 inches
9. No. of Picture element 61,380 (220 ×279) dots
10. Dimensions 115 (W) ×61.7 (D) ×112 (H) mm
4 1/2(W) ×2 2/5(D) ×4 2/5(H)
11. Weight 360 g excepting batteries
12.7 oz excepting batteries
AC adaptor : AD-K65,64
12. Options Car adaptor : CA-K65
RF connector : CF-13
Antenna matching device : AS-35S

— 3 —
BLOCK DIAGRAM
TV
1— Color tuner: TU200 TEPU5-02
Selects a desired radio wave and changes it to the video IF signal.
2— Video IF amp.: Q200 2SC4238
Amplifies the video IF signal output from tuner TU200 by 10 times (20 dB).
3— Video det./Sound det./FM det./AFT/AGC: IC200 M51348FP
EliminatesthecarrierwaveinthevideoIFsignal,andpicksupthevideosignalandthesoundIFsignal.
Also, the sound signal is picked up from the sound IF signal by FM detection.
4— Audio amp.: IC600 NJM2070M
Sound amplification.
5— Chroma circuit: IC300 IR3P90Y
Generates the tricolor (red, green, and blue) from the video signal.
6— Display control/Auto-tuning control: IC700 MSM6770GS
Controls the display.
7— Tuning voltage generator: IC270 BA10358F
Generates the tuning voltage with the tuning pulse output from 6.
Antenna
1 TU200 2 Q200 3 IC200
7
Tuning
Voltage
Generator
VR600
Volume
Control
4 IC600 Speaker
IC300
IC700
LCD
Chroma
Circuit
Display
Control
Auto-Tuning
Control
5
6
VCC1 (4.5 ± 0.05 V)
VCC2 (4.5 ± 0.05 V)
VCC7 (25.9 ~ 31.3 V)
VCC6 (10.0 ~ 12.0 V)
VEE1 (–8.0 ~ –7.0 V)
VEE2 (–18.4 ~ –16.0 V)
IC270
Power
Supply
Audio
Amp.
IF Amp.Tuner
Video
Sound Det.
FM
AFT Circuit
AGC Circuit
Det

— 4 —
Figure 1
CIRCUIT DESCRIPTION
Name Voltage Function
VCC2-1 4.50 ±0.02 V Main voltage
VCC7 25.9 ~ 31.3 V Tuning voltage
VCC6 10.0 ~ 12.0 V Display voltage
VEE1 –8.0 ~ –7.0 V Display voltage
VEE2 –18.4 ~ –16.0 V Display voltage
Table 1
The power supply consists of a DC-DC converter and the associated circuit and supplies the voltages as shown
in Table 1.
POWER SUPPLY
CP105
R108
270K
R110
270
Q110 2SD1819A-R
Q111
2SD1119-R
C137
R107
D100
MA141K 33K B6800p
C140
CH470p R115
100
6.3 V 220C100
D110
MA3051-L
2.2
BH102K
TM100
Q101
2SD1819A-R
2.2KR113
R105
3.3K
VR100
2K
C105
C145
B1500p
CP106
1
2
9
6
3
4
5
6
7
8
T100
LC12U-35 D158 MA143A R160
68
C146 OPEN
D156 MA141K
D154 MA142WK
D150
MA142WK
D152
MA142WK
L101
100u
L103
100u
CP110
CP111
CP113
CP114
CP115
C110 25 V 10 C112 16 V 47 C114 6.3 V 100 C116 6.3 V 100 C118 16 V 22 C120 35 V 22 R161 33K
VEE2 (-18.4 ~ -16.0 V)
L102
100u
R100
0R00
GND
CP112
1
2
3
VEE1 (-8.0 ~ -7.0 V)
VCC2-1 (4.5 V)
VCC6 (10.0 ~ 12.0 V)
VCC7 (25.9 ~ 31.3 V)
VCC2-2 (4.5 V)
VCC2-3 (4.5 V)

— 5 —
DISASSEMBLY
1. Remove the battery case.
2. Remove the three screws and the lower case.
3. Remove the three knobs.
4. Remove the screw and resolder the two wires for the speaker.
5. Remove the PCB ass'y.

— 6 —
DIAL STRINGING DIAGRAM
92
10
3
8
4
A5
7
6
Turn the pulley counterclockwise.
Wrap around 4 times.
0.8 mm
Sliding pointer

— 7 —
ADJUSTMENT
TV
Items to Be Adjusted
Item Measuring Instrument
VCC2-1 voltage setting Voltmeter
Video detection coil adjustment TV signal generator, pattern generator, oscilloscope,
low-pass filter
AFT coil adjustment Sweep generator, oscilloscope, voltmeter
Contrast adjustment TV signal generator, pattern generator, oscilloscope
Tint adjustment TV signal generator, pattern generator, oscilloscope
AGC adjustment TV signal generator, pattern generator, IF levelmeter
Vcom adjustment Photo diode, photo sensor amp., bandpass filter, oscilloscope
Free-Running frequency adjustment Frequency counter
RADIO
When the radio is defect, replace the radio PCB unit.
Adjustment and Test Point Locations
Top View
T201
T200
VR200
VR303
VR301
VR300
VR100
VR740

— 8 —
VCC2-1 Voltage Setting
Input Input Input Output Output
Connection Point Signal Connection Point
Adjust Result
Adjust to obtain a 4.50 ±0.02 V
reading on the voltmeter.
Voltmeter
VR100 TP1
TP1
16-169
Equipment Connection / Adjustment Procedure
Output
Voltmeter
EV-2500
set
TP7(CP204)
TP2(CP201)
IF Pad
TP4(CP217)
TP3(CP218)
TP1(CP113)
TP6(CP311)
TP8(CP320)
TP5(CP323)
Bottom View

— 9 —
2.2 ± 0.1 V
P.P
Video Detection Coil Adjustment
TP2 VR300 TP5
Pattern
generator
Signal
generator
Oscilloscope
* Desolder the IF pad to open.
Contrast Adjustment
TP2 T201 TP4
Adjust to obtain a 1.4 ±0.2 V
reading on the voltmeter.
Confirm that the marker is at
the middle of the S-curve on
the oscilloscope.
* Desolder the IF pad to open.
AFT Coil Adjustment
Pattern
generator
Signal
generator
TP2 T200 TP3
Input Input Input Output Output
Connection Point Signal Connection Point
Adjust Result
* Desolder the IF pad to open.
Voltmeter
Oscilloscope
Sweep
generator
Pattern
generator Signal generator
Input
TP2
CP312 (KILLER)
Oscilloscope
Vcc2-3
EV-2500
set 10 kohm
Adjust so
that the step
form wave
becomes 2.2
±0.1 Vp-p.
Adjust to obtain the minimum
DC level.
Low-pass filter
Oscilloscope
Input
TP2
EV-2500
set
Output
TP3
Low-pass
filter
Pattern
generator Signal generator Oscilloscope
Sweep
generator EV-2500
set
Input
TP2 Output TP4
Voltmeter
Oscilloscope
Color bar
45.75 MHz
45 ±3 dBµ
Output
TP5
38.9 ±5 MHz
(sweep) marker:
45.75 MHz
70 ±3 dBµ
Color bar
45.75 MHz
70 ±3 dBµ