CASIO AT1 Service Manual

AT-1

INDEX

(without price)

ELECTRIONIC KEYBOARD

CONTENTS

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Replacing the DSP (HG51B155FD) . . . . . . . . . . . . . . . . . . . . . . . . 2

Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Circuit Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Wiring Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Major Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

PCB View and Major Check Points . . . . . . . . . . . . . . . . . . . . . . . 14

Schematic Diagrams. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Exploded View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

IC Lead Identification and Internal Diagram . . . . . . . . . . . . . . . . 19

Parts List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

SPECIFICATIONS

General

Number of Keys: 61
Polyphonic: 32-note
Preset Tones: 100

Tone Expander: Layer, Split

Keyboard Controls: Touch Response: On/Off

Touch Sensitivity: Light/Middle/Heavy
Key Transpose: Range from F# to F by a semitone increment
Oriental Scale Control: Tune: On/Off, Mode: Cent/

Tuning Rang: Quarter tone (±99 cents) and
Scale Memories: 4
Auto-Rhythms: 50

Tempo Control: 40 to 255
Auto-Accompaniment: CASIO Chord/Fingered/Full-Range Chord

Controller: Variation, Fill-In, Intro/Ending
Magical Presets: 50; BREAK BEAT 20

FREE SESSION 24
KEY SPLIT 6

Digital Effects: 10; Reverb-1, Reverb-2, Reverb-3, Chorus, Tremolo, Phase Shifter,

Organ SP, Enhancer, Flanger, EQ Loudness
Sound/Control Pads: 4
Pad Variations: 32; Phrases: 10, Drums: 10, Percussion: 10, Controllers: 2
Song Memory: 1; System: Real-time recording

Memory Capacity: Approx. 700 notes
Pitch Bender: Bend Range; 2 semitones/3 semitones
Registration Memories: 6
Registration Items: Tone Number, Rhythm Number, Tempo, Accompaniment Mode,

Accompaniment Volume, Effects, Layer On/Off, Split On/Off,
Chord On/Off, Accompaniment Scale On/Off, Pad Variation,
Assignable Jack, Auto-Accompaniment Controller, MIDI (Channel On/Off,

GM On/Off, Local Control On/Off, Bend Range)
Tuning Control: 440Hz ± 50 cents
Terminals: Headphone Jack [Output Impedance: 150 Ω, Output Voltage: 5.2 V(rms)

MAX], Assignable Jack, MIDI Jacks (IN, OUT), AC Adaptor Jack (9 V)
Built-In Speakers: 12 cm dia. 2.5 W Input Rating: 2 pcs.
Power Source: 2-way AC or DC source

AC: AC adaptor AD-5

DC: 6 D size dry batteries

Battery life: Approx. 5 hours by manganese batteries R20P(SUM-1)
Auto Power Off: Approximately 6 minutes after the last operation
Power Consumption: 7.7 W
Dimensions (HWD): 129 x 942 x 367 mm

5-1/16 x 37-1/16 x 14-7/16 inches
Weight: 5.3 kg (11.7 lbs) excluding batteries
Standard Accessory: Music stand, Dust cover

Koma

koma

(±5

komas

)

— 1 —

Electrical

Current Drain with 9 V DC:
No Sound Output 260 mA ± 20%
Maximum Volume 930 mA ± 20%

with key C3 pressed in Synth-Bass tone and effect No. E-9
Split: On, Layer: On, Oriental scale: On/Cent
Song memory: Play, Volume; maximum, Touch: maximum

Line Output Level (Vrms with 47 KΩ load each cannel):

with key F2 pressed in FSynth-Bass tone 2480 mV ± 20%

Phone Output Level (Vrms with 8 Ω load each channel):

with key C3 pressed in FSynth-Bass tone 97 mV ± 20%

Speaker Input Level:

with key C3 pressed in FSynth-Bass tone 2240 mV ± 20%

Minimum Operating Voltage: 6.3 V

REPLACING THE DSP (HG51B155FD)

Note: To increase productivity ,the DSP HG51B155FD is sticked on the main PCB with a double-side
adhesive tape, then its leads are soldered.

Remove the DSP according to the following procedures.

1. Prepare isopropyl alcohol and a flat IC desoldering machine (Spot Heater HS-600).

2. Apply plenty of the alcohol to the adhesive tape from the reverse side of the main PCB. (Fig.1)
There is a hole on the PCB just under the LSI, and the adhesive tape can be seen through the hole.

3. Leave it more than one minute so that the alcohol weaken adhesive power fully.

4. Using a proper size of nozzle, apply heat to leads of the LSI with the desoldering machine.

5. Grasp the LSI with tweezers, and using gentle force vibrate the tweezers to feel melting solder. (Fig.2)

6. Remove the LSI after meltingsolder at every leads wholly.

Spot Heater HS-600

Alcohl

HG51A115A

LSI-S

— 2 —

Fig.2Fig.1

BLOCK DIAGRAM

Keyboard

FI0 ~ FI7

SI0 ~ SI7

Key Touch LSI

LSI106

HG52E35P

KC0 ~
KC7

A0 ~ A2

Reset IC

IC104

RE5VA35AA

Working Strage

RAM (64K-bit)

LSI104

SRM2264LC90,10

A0 ~
A12

D0~D7

A0 ~ A14

Q109 ~ Q116

A0 ~ A3

La ~ Lg, Lp

LED driver

LD0 ~ LD7

RESET

CPU

LSI102

HD6433298A36P

7-Seg.

LED

LEDs

CLK

KO

LC1 ~ LC4

LO0 ~ LO4

KO Signal
Generator
IC303/304

TC74HC174P

KI1 ~ KI7

POWER

Power Switch

LED driver
IC301/302
BA612

KO0 ~ KO10

Buttons

VDD

MIDI

OUT

IN

Effect RAM

(64K-bit)

LSI107

SRM2264LC90,10

Speakers

EA0 ~ EA12

ED0 ~ ED7

Output

DSP

LSI105

HG51B155FD

WCK1 SLOP BCK

D/A Converter

LSI101

UPD6376CX

Filter

IC105

Main
Volume

Power Amplifier

IC102

LA4598

Filter

IC105

RA0 ~ RA19

RD0 ~ RD15

VC

Sound Source ROM

(16M-bit)

LSI103

TC5316200CP-C106

APO

LVDD

VCC

Power Supply Circuit

AVDD

IC101, Q1 ~ Q4

DVDD

VDD

— 3 —

CIRCUIT DESCRIPTION

Key Matrix

KC0 KC1 KC2 KC3 KC4 KC5 KC6 KC7
FI0 C2 1 C#2 1 D2 1 D#21 E2 1 F2 1 F#21 G2 1
SI0 C2 2 C#22 D2 2 D#22 E2 2 F2 2 F#2 2 G2 2
FI1 G#21 A2 1 A#2 1 B2 1 C3 1 C#3 1 D3 1 D#3 1
SI1 G#22 A2 2 A#2 2 B2 2 C3 2 C#32 D3 2 D#32
FI2 E3 1 F3 1 F#3 1 G3 1 G#31 A3 1 A#3 1 B3 1
SI2 E3 2 F3 2 F#3 2 G3 2 G#32 A3 2 A#3 2 B3 2
FI3 C4 1 C#4 1 D4 1 D#4 1 E4 1 F4 1 F#4 1 G4 1
SI3 C4 2 C#4 2 D4 2 D#4 2 E4 2 F4 2 F#4 2 G4 2
FI4 C4 1 C#4 1 D4 1 D#4 1 E4 1 F4 1 F#4 1 G4 1
SI4 C4 2 C#4 2 D4 2 D#4 2 E4 2 F4 2 F#4 2 G4 2
FI5 E5 1 F5 1 F#5 1 G5 1 G#51 A5 1 A#5 1 B5 1
SI5 E5 2 F5 2 F#5 2 G5 2 G#52 A5 2 A#5 2 B5 2
FI6 C6 1 C#6 1 D6 1 D#6 1 E6 1 F6 1 F#6 1 G6 1
SI6 C6 2 C#6 2 D6 2 D#6 2 E6 2 F6 2 F#6 2 G6 2
FI7 G#61 A6 1 A#6 1 B6 1 C7 1
SI7 G#62 A6 2 A#6 2 B6 2 C7 2

Note: Each key has two contacts, the first conatct 1 and second contact 2 .

Key

FI

Second contact 2

First contact 1

KC

SI

Nomenclature of Keys

C#2

F#2D#2

C#3A#2G#2

D#3

F#3 G#3

A#3 C#4 D#4

F#4 G#4

A#4

C#5

D#5

F#5 G#5

A#5

C#6

G#6F#6D#6

A#6

C2 D2E2F2

G2

A2 B2 C3 D3

E3

F3 G3 A3 B3 C4 D4 E4 F4 G4 A4 B4 C5 D5 E5 F5 G5 A5 B5

— 4 —

C6

B6A6G6F6E6D6

C7

Button Matrix

KI1 KI2 KI3 KI4 KI5 KI6 KI7

KO0 Registration 3 2 1 0

KO1 Control Demo Layer Split

KO2 Tone Rhythm 9 8 7 +

KO3 Accomp 6 5 4 -

Transpose/

Tune

Magical

Preset

Digital

Effect

Memory

Touch

Response

KO4 G# down A down A# down B down G down

KO5 ScaleMode ScaleTune B up A# up A up G# up G up

Song

KO6 Intro Start/Stop

Tempo

Down

Tempo

Up

Synchro/

Ending

Variation/

Fill-In

Normal/

Fill-In

KO7 C up C# up D up D# up E up F up F# up

KO8 C down C# down D down D# down E down F down F# down

KO9 Mode Pad B Pad D Pad A Pad C

KO10 Rec

Scale

Memory 1

Scale

Memory 2

Scale

Memory 3

Scale

Memory 4

Reset Circuit

Initial reset
When batteries are set or an AC adapter is connected, the reset IC provides a low pulse to the CPU.
The CPU then initializes its internal circuit and clears the working strage RAM.
Power ON reset
When the power switch is pressed, the CPU receives a low pulse of POWER signal. The CPU provides
APO signal to the power supply circuit, then provides RESET signal to the DSP, the key touch LSI and
the KO signal generators.

VDD

From power switch

Battery set

Reset IC

IC104

RE5VA35AA

RESET

POWER

VDD

CPU

LSI102

HD6433298A36P

-NMI

-RESET

DVDD

KO Signal Generator

IC303/304

TC74HC174P

Working Strage RAM

LSI104

SRM2264LC90,10

HG51B155FD

VDD

Key Touch LSI

LSI106

HG52E35

DVDD

DSP

LSI105

DVDD

— 5 —

CPU (HD6433298A36P)

The 16-bit CPU contains a 32k-bit ROM, a 1k-bit RAM, seven 8-bit I/O ports, an A/D convertor and serial
interfaces. The CPU accesses to the working strage RAM, the DSP and the key touch LSI. The CPU also
controls buttons, bender input, LEDs and MIDI input/output.
The following table shows the pin functions of the CPU.

Pin No. Terminal In/Out Function

1 P40 Out KO signal data output
2 P41 Out Clock for KO signal data
3 P42 Out APO (Auto Power Off) signal output. ON: High OFF: Low
4 P43 Out Read enable signal output
5 P44 Out Write enable signal output
6 P45 Not used
7 P46 Out 10 MHz clock output
8 P47 In Wait signal input. Connected to +5 V.

9 TXD Out MIDI signal output
10 RXD In MIDI signal input
11 P52 Out Reset signal output
12 -RESET In Reset signal input
13 -NMI In Power ON signal input
14 VCC In +5 V source
15 -STBY In Standby signal input. Connected to +5 V.
16 VSS In Ground (0 V) source

17, 18 XTAL,EXTAL In 20 MHz clock input
19, 20 MD1, MD0 In Mode selection input.(Internal ROM mode --- MD1: High MD0: Low)

21 AVSS In Ground (0 V) source for the built-in DAC
22 AN0 In Analog input. Connected to ground.

23 ~ 29 P71 ~ P77 In Ternimal for button input signal

30 AVCC In +5 V source for the built-in DAC

31 ~ 38 P60 ~ P67 Out LED segment signal output

39 VCC In +5 V source
40 P27 Not used

41 ~ 56 P26 ~ P10 Out Address bus

48 VSS In Ground (0 V) source

57 ~ 64 P30 ~ P37 In/Out Data bus

Digital Signal Processor (HG51B155FD)

Upon receipt of note numbers and their velocities, the DSP reads sound and velocity data from the sound
source ROM in accordance with the selected tone; the DSP can read rhythm data simultaneously when a
rhythm pattern is selected. Then it provides 16-bit serial signals containing data of the melody, chord,
bass, and percussion to the DAC. The DSP also adds the selected effect to the sound data using a 64k-bit
RAM.
The following table shows the pin functions of the DSP.

— 6 —

Pin No. Terminal In/Out Function

1 ~ 8 CD0 ~ CD7 In/Out Data bus
9, 10 Not used

11 GND7 In Ground (0 V) source
12 CK16 Out 16.384 MHz clock output
13 VCC6 In +5 V source
14 CK0 In Clock input. Connected to terminal CK16.
15 TCKB Not used
16 VCC1 In +5 V source
17 GND1 In Ground (0 V) source

18, 19 XT0, XT1 In/Out 16.384 MHz clock input/output. Connected to a crystal oscillator.

20 SGL In System control terminal. Single chip system: Open
21 CCSB In Chip select signal input

22 ~ 25 CA0 ~ CA3 In Address bus

26 CE0 In Not used. Connected to ground.
27 CWRB In Write enable signal
28 CRDB In Read enable signal

29 ~ 32 Not used

33 RESB In Reset signal input
34 TESB In Not used. Connected to +5 V.

35 ~ 39 Not used
40 ~ 49

52 ~ 57

RD0 ~ RD15 In Address bus for the sound source ROM

50 VCC2 +5 V source
51 GND2 Ground (0 V) source
58 RA23 Out Not used
59 RA22 Out Chip select signal for the sound source ROM

60, 61 RA20, RA21 Out Not used

62 ~ 73
75 ~ 82

RA0 ~ RA19 Out Address bus for the sound source ROM

74 GND5 In Ground (0 V) source
83 WOK2 Out Word clock output. Not used.
84 VCC3 In +5 V source
85 GND3 In Ground (0 V) source
86 WOK1 Out Word clock for the DAC
87 SOLM Out Serial data output. Not used.
88 SOLP Out Serial sound data output for the DAC
89 BOK Out Bit clock output for the DAC

90 ~ 92 Not used

93 VCC5 In +5 V source
94 EA14 Out Not used

95, 97

99 ~ 105
107, 109

EA0 ~ EA12 Out Address bus for the effect RAM

110, 112

— 7 —