Casio SK-5 - SERVICE Troubleshooting guide

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ELECTRONIC
KEYBOARD
K
MAR.
1987
Service
MANUAL
а
PARTS
L
J J IP AI I IP I LE I DH DT Pa [1 IP H IP I اا󰾯 IP AT AT IP IP AT IP IP ¦" IT

СОМТЕМТ$
1. SCHEMATIC DIAGRAM
1-1. PCB M3126-MA1M ............................................ 1
1-2. PCB M3126-CNIM ............................................. 2
1-3. PCB МАТОВ М ο aset sums Meth Аы سە󰾯 3
14. Keyboard РСВ M3129-KY1M .................................... 4
2. РСВ VIEW & MAJOR CHECKPOINTS .................................. 5
3. MAJOR WAVEFORMS.............................................. 6
4. BLOCK DIAGRAM.................................................. 7
5. KEY & SWITCH MATRIX ............................................. 8
6. CPU (MSM6283-05GS) .............................................. 9
7. PERCUSSION GENERATOR (MSM6294-02) ............... ΠΡ N 11
8 MELODY CIRCUS Ades ee да ы о ae fe bets ae 12
9. ‘SAMPLING CIRCUIT ............................................... 13
10. PERIPHERAL DEVICE ACCESS ...................................... 14
11. DEMO MUSIC ROM ACCESS ......................................... 15
12. ВЕЗЕТ & POWER ON/OFF DETECTION CIRCUIT........................ 16
13. POWER SUPPLY CIRCUIT ........................................... 17
14. “TROUBLESHOOTING ae ¥ ean et us εν 18
PARTS LIST .......... ERBE EEE Απ ο CPP ` "¦ ك󰾯 19
© m τ m ΠΙ m ΠΙ © Π m © ΠΙ ΠΙ Π m ἩΙ M ΠΙ Π H ON ΤΙ HM N OHN ON ¦] | | | ΠΠ.

SCHEMATIC DIAGRAM 1.
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РСВ M3126-MA1M
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1-2. РСВ М3126-СМ1М а " я Б 2
4
=== ==
KH K12 |
5 Воск 1 Воск 2
KI3 KI4 ۸12 هل󰾯
Disco 1 Disco 2 MEMORY sm
Kli KI2 S16 omes
16 Beat March TEMPO [4]
6 КІЗ к14 SIS چ لم󰾯
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MELODY GUIDE Slow Rock Waitz MEMORY STOP
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1-3.
PCB M3126-CN2 A
2
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1
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Keyboard PCB M3129-KY 1M
1-4.
КГН 60-52-97
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2. PCB VIEW & MAJOR CHECKPOINTS
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3. MAJOR WAVEFORMS
Notes: Photographs of waveforms have been taken using a memory scope.
Attenuation Radio of probes 10:1
(1) RESET signal (2) Signal MI
When AC adaptor is inserted At Power ON
0.2V /div., 0.1 sec/div. 0.2V/div , 1ms/div
(3) CPU clock (5) Signal SH
Percussion Generator Clock (6) Melody Circuit Output
0.2V /div., 0.5us Tone: Pipe Organ
Key: C2
5OmV /div., ims/div.

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4. BLOCK DIAGRAM
РР

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5. KEY & SWITCH MATRIX
Dog
Sample
2
Memory | Memory
Sample
Long
KO6 Rock 1
=
16 Beat
K
07
= كت󰾯
KO11 Accomp.
Chorus
Sample
3
Disco 1 Disco 2
Bossa Nova | Samba
Sample |Sample
Pad 2 Pad 3
Rhythm Pad
Hi- Low Lion
Bongo Bongo

6. CPU (MSM6283-05GS)
© Generates Pitch and Envelope signals for Melody, Chord, Bass and Obbligato sounds.
o Controls Keys, Switches and peripheral devices.
The following table is the pin functions of the CPU.
————— €
Pin No. |Terminal Name In/Out Function
1 BGND 5V source for internal ADC (Analog to Digital Converter)
2 VADC Ground (OV) source for internal ADC
T
3,4 No function
5-11 100—106 In/Out Data bus (DO ~ D6)
12 AO Out Address bus (А0)
13 107 In/Out | Data bus (D7) |
14 A1 Out Address bus (A1)
15 CE Out Chip enable signal for memory devices. LOW active.
T
16-18 | A2, A10, АЗ Out Address bus (A2, A3, A10)
19 No function
20~29 | A4~9, А11~14 Out Address bus (A4 ~ A9, A11 ~ A14)
30 | A15 Out Output enable signal for memory devices. LOW active.
31 WE Out Write enable signal for RAM. LOW active.
32—38 No function ]
39 CE1 Out Write enable signal for Percussion generator. LOW active.
40 GND 5V source
41 CE2 Out ROM pack’s chip select signal. LOW active. I
42 No function
43 VDD1 | Ground (OV) source for internal digital circuit
44 VDD2 Ground (OV) source for internal analog circuit
45 No function
----- — ο.
46, 47 CP1, СР2 Out ROM pack’s clock pulse
—
48 ОР Out Demo Music КОМ” data/address change signal.
| Data bus for Demo Music ROM becomes data or address in accordance
| with the voltage level of this signal.
49~52 | DO~D3 Out Data bus for Percussion generator.
T — =
53-56 | 04-07 Out Data bus for Percussion generator and data/address bus for Demo
| Music ROM.
4
57,58 | OSI, OSO In/Out 7.277 MHz clock pulse input and output.
d
58 ¦ MI In Power ON detection signal input. HIGH active.
| | Receiving а pulse at Power ON, CPU starts functioning.
| 60 ВЕЗЕТ т Reset signal input. HIGH active.
The terminal receives a pulse which resets CPU internal circuit when
new batteries or AC adaptor is set.
61 | No function
2 Ah Е
82 KO14 Out | Accompaniments’ volume control signal.
53 1 3 Out ROM and RAM chip select signal.
| ىلىي󰾯 Е
-
1

Sampling
CPU
internal
clock
86-88 | РОТ ~ РОЗ
E EH
the internal circuits of the Percussion generator are initialized.
Pin No. | Terminal Name In/Out Function |
64 O12 Out APO (Auto Power Off) signal output.
Terminal drops to LOW level to shut the voltages off when the unit is
not operated for approximately 6 minutes.
65~76 KO11-—KOO Out Key common signals.
77-84 КИ ^ KI8 In Key input signals
85 POO Out Reset signal for Percussion generator.
The terminal holds LOW level at power ON for a while during which
— F
No function
89 EH Out Melody envelope signal output
90 EG Out Melody or obbligato envelope signal output
91 EF Out Melody or chord envelope signal output
92 EE Ош Melody or bass envelope signal output
93 SH Out Melody pitch signal output |
94 SG Out Melody or obbligato pitch signal
95 SF ow | Melody or chord pitch signal
96 SE Out Melody or bass pitch signal
97 No function
98 AGND +5V source for DAC (Digital to Analog Converter)
99 Ground (OV) source for DAC
VDAC
Sampling sound ínput signal from MIC terminal
190
107
Sampling E
read
clock
Read Cycle {+ pulse refresh)
Timing chart of sampling CPU for ROM and RAM
Write Cycle (* pulse refresh]
| Floating Cycle {+ pulse refresh)
— 10 —
t= 1/fPG (=7,802MHz)
Lei
3
r dj

7. PERCUSSION GENERATOR (MSM6294-02)
Containing
a
internal
ROM
(128
Kbit)
for
percussion
data,
and
internal
8
bit
DAC
(Digital
to
Analog Converter),
the LSI provides
percussion
sounds.
Percussion
Out
Data Bus
CPU
Percussion
Percussion Filter
MSM6293
Generator
MSM6294
WR
Oscillator
fo =256 KHz
Pin Function of Percussion Generator
ЕП Мо. Signal In/Out | Function
1 RESET in Reset signal input. LOW active.
| The terminal holds LOW level at power switch on for initializing the internal
circuit
2 | CLK In Clock pulse (256 kHz) input
3 | _| No function
4 | WR In Write signal input. LOW active.
| The LSI reads the percussion data from the CPU when the terminal
| is LOW level.
5 | CS In Chip select signal input. Fixed at LOW level.
6-3 | 0-07 In Data bus (DO ~ D7)
14 DVSS Ground (OV) source for internal digital circuit
15,16 | No function
17 | AVSS Ground (QV) source for internal DAC
18 MIX-O Out Analog percussion signal output
| 18 | AVDD | +5\/ source for internal DAC
| 20-27 No function
| 28 | DVDD +5V source for internal digital circuit
E ect

8. MELODY CIRCUIT
| AM : i Melody or
68K : Obbligato
s
A,
ix
Melody
or
47K
:
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Bass
|
J
Pitch
2.5V
220K
[De
Envelope
EF
5
|
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Gain
Controller
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3
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Pitch
SH
I
22
Envelo
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=
=
0—4
|
|
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AB
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CA91A02
MSM6283
CPU outputs four each of pitch and envelope signals.
Normally all the signals are for melody sounds however, when the demonstration music is played,
each pitch and envelope signals become obbligato, bass, chord, or melody sounds.
CA91A 02 contains four mixing amplifiers and merges each pitch and envelope signals.
Gain Controller balances the sound volume of melody and accompaniments for demonstration
music. Signal KO14 normally stays HIGH level so that all the switches turn on. When the demon-
stration music is played, KO14 falls to LOW level turning the switches off and all the accompaniment
signals are reduced as they pass through the resistors.
I pe

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===
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9. SAMPLING CIRCUIT
νο
Internal MIC
External MIC
CPU
MSM6283-02Gs "Vin У
τ
e
2
Line-in
MIC Amp.
Circuit
VL1
Fig. 1 Sample Sound Input Circuit
VC
Sampling
Sound
—
F
Input
Signal
Te
su
fear
Sampling
Start
Area
E EE +0.315V 1
= er ¬¬ Es Vin (2.557V)
dU 2242N
Sampling
Start
Sampling Start Area
Fig. 2 Vin Input Trigger Level
As shown in Fig. 1, the circuit provides sampling signals to the Vin terminal of the CPU. Resistors
100Kohm and (100 + 4.7) Kohm bias the sampling signal on 2.863V.
When the sampling sound level exceeds € 0.315V as shown in Fig. 2, the CPU starts to transmit
the sampling sound data to the RAMs during the following period.
While sampling, the CPU transmits the sampling sound data to the sampling RAMs directly.
While sampling, CPU does not output key common signals (КОО ~ KO9) so that the keyboard
becomes inoperative.
Sampled sounds are digitized in CPU and transmitted to the ВАМ.
—13—