Korg A4 Guitar User manual

SERVICE MANUAL
CONTENTS
1. SPECIFICATIONS 1
2. STRUCTURAL DIAGRAM 3
3. BLOCK DIAGRAM 5
4. CIRCUIT DIAGRAM 6
5. P.C. BOARDS 7
6. HOWTO DISASSEMBLY 9
7. DIAGNOSTIC TEST 11
8. REFERENCE DATA 18
9. PARTS LIST 26

1. SPECIFICATIONS
FOR A4GTR
Internal Effects :COMPRESSOR, DISTORTION/OVERDRIVE, 3BAND EQ, PITCH/DELAY,
CHORUS/FLANGER, REVERB, AMP SIMULATION, NOISE REDUCTION
Programs :Preset; 30 programs
User programable’, 30 programs
Front panel :Volume; INPUT VOLUME, PARAMETER EDITORS, OUTPUT VOLUME
Keys/Switches; BANK UP SWITCH, WRITE KEY, USER/PRESET KEY,
BYPASS/TUNE SWITCH, EFCT/PROG SWITCHES, PROG/EDIT SWITCH,
MODE(Effect)SELECT KEYSCUP, DOWN)
Display; BANK/VALUE Display (8 segment LED x2)
Dot type LEDs; EFCT/PROG LEDs, MODE LEDs, Peak indicator
Rear panel :Power Switch, DC9V Jack, INPUT Terminal, OUTPUT Terminals
(L/MONO, R), PHONE Jack, VOLUME PEDAL Jack, EXTERNAL CONTROL
OUTPUT Terminals (1, 2), MIDI Terminals (MIDI IN, MIDI OUT)
Sampling Frequency.* 48 KHz
Dynamic Range :90dB or more(IHF~A, when bypassing)
TUNER :Measurement Range; A0-C7
Measurement Accuracy; ±0.5 cent.
Power Supply •DC9V
Power Consumption ;350mA
Maximum Input
Level/Impedance *. +7dBu/lMQ
Maximum Output
Level/Impedance :+7.5dBu/lkQ
Dimensions •498(W) x227.5(D) x48.7(H)mm
Weight :2.2kg
1

FOR A4BASS
Internal Effects :
Programs :
Front panel :
Rear panel :
Sampling Frequency:
Dynamic Range :
TUNER :
Power Supply :
Power Consumption :
Maximum Input
Level/Impedance :
Maximum Output
Level/ Impedance :
Dimensions :
Weight :
COMPRESSOR, DYNAMIC EXCITER, 6BAND EQ, SYNTH BASS, DELAY,
CHORUS/FLANGER, REVERB. NOISE REDUCTION
Preset; 30 programs
User programablej 30 programs
Volume; INPUT VOLUME, PARAMETER EDITORS, OUTPUT VOLUME
Keys/Switches; BANK UP SWITCH, WRITE KEY, USER/PRESET KEY,
BYPASS/TUNE SWITCH, EFCT/PROG SWITCHES, PROG/EDIT SWITCH,
MODE(Effect)SELECT KEYS(UP, DOWN)
Display; BANK/VALUE Display (8 segment LED x2)
Dot type LEDs; EFCT/PROG LEDs, MODE LEDs, Peak indicator
Power Switch, DC9V Jack, INPUT Terminal, OUTPUT Terminals
(L/M0N0, R), PHONE Jack, VOLUME PEDAL Jack, EXTERNAL CONTROL
OUTPUT Terminals (1, 2), MIDI Terminals (MIDI IN, MIDI OUT)
48 KHz
90dB or more( IHF-A, when bypassing)
Measurement Range; A0-C7
Measurement Accuracy; ±0.5 cent.
DC9V
350mA
+7dBu/lMQ
+7.5dBu/lkQ
498(W) x227.5(D) x48.7(H)mm
2.2kg
*Specifications, operations and appearrance are subject to change without notice.

2. STRUCTURAL DIAGRAM
PART NO
(§>
PART CODE
745060308
715260308
715230308
540019600
i
HHSjjB PART NAME PART CODE
iX-150G CASE ASSEMBLY (A4 CTR) 646043400
lX-150B CASE ASSEMBLY (A4 B) 646043500
2X— 150 CHASSIS 641034600
3X-150 PHONE JACK SUPPORT 641034500
4X-150G PARAMETER SHEET (A4 GTR) 630018500
4X-150B PARAMETER SHEET (A4 B) 630018600
5ROTARY VR KNOB 620022900
6X-150 CORD HOOK 646043000
7POWER SW KNOB 620018200
8RUBBER SPACER K0C-40577 500019600
9
10
RUBBER FOOT 3x22x3
NAME SEAL
500018300
11 X-507 GND SPRING 644003000
12 P.C.B. ASSEMBLY KLM-1597 (MAIN FOR A4G) 001159700
12 P.C.B. ASSEMBLY KLM-1597 (MAIN FOR A4B) 0011597P1
13 P.C.B. ASSEMBLY KLM-1598 (PANEL) 001159800
14 P.C.B. ASSEMBLY KLM-1599 (REGULATOR) 001159700

m
UPPER CASE ASSEMBLY
PART NO PART NAME PART CODE
1X-150G CASE 646042700
1X-150B CASE 646043100
X- 150 PEDAL 646042800
SW CUSHION KOC-F40427 500013100
PEDAL SPRING K0C-C40896 644006400
5X-150 REFLECTOR 646042900

INPUT
LEVEL
A/D LPF
DSP D/A OUTPUT
L/MONO
LEVEL IND.
CURCUIT
LEVEL
IND .
TUNE
TUNER
CIRCUIT
1^L-J-j j
{^
MUTE
CURCUIT
wDRAM OUTPUT
LEVEL
CPU
ROM 256Kbit
RAM 6Kbit
PHOTO
COUPLER
'n PHONI
*V MINI
MIDI OUT
VOL
PEDAL
EXT
CONTROL
SWITCH LED
—-H
mm tIv*
BANK/PROG
VALUE PARMETER
.
BLOCK
DIAGRAM

4. CIRCUIT DIAGRAM
KLM-1 597/98/99
INPUT
LOR *501- 8000
LOR 4302’ 8000
6

5. P.C. BOARDS

6. HOW TO DISASSEMBLY
1. Remove the case assembly
1) Remove 8pcs. of the rotary VR knobs on the upper case.
2) Remove 16 pcs. of the screws on the chassis.
[PLAX BBZMC 3x10 ]x16
3) Remove 2pcs. of the harnesses and remove the case assembly.

2. Remove the panel p.c. b. (KLM-1598)
1) Rmove 2pcs. of the screws on the panel p.c.b. and remove it.
CPLAX BBZMC 3x10 ]x2
3. Remove the main p.c. b. (KLM-1597/99)
1) Remove ascrew on the regulator.
[CT BBZMC 3 x 8]x1
2) Remove 4pcs. of the screws on the rear side of the chassis
and remove the main p.c.b..
for PHONE JACK SUPPORT :[CT BBZMC 3 x 8]x2
for MIDI JACK :[PLAX BBZMC 3x10 ]x2
10

7. DIAGNOSTIC TEST
<BEFORE ACTIVATING THE TEST MODE >
The A4 GTR and BASS have atest mode for checking the unit’s functions.
When this test mode is activated, the data in the A4 is not initialized.
Nevertheless, the data could be initialized by mistake, so it is advisable
to save any user data to aMIDI data filer.
If necessary, the data in the A4 can be returned to the factory settings (preload
data) by carrying out the operation for setting preload data after this test mode
is activated.
The required equipment and settings for the test mode are pictured below.
<SETUP FOR TEST >
<D INPUT
©OUTPUT L/MONO & R
©VOLUME
®EXT. CONTROL OUT 1&2
©MIDI IN &MIDI OUT
<0. ACTIVATING THE TEST MODE >
(1) Switch the power on while at the same time pressing both the [USER/PRESET]
and [WRITE] buttons on the front panel. The test mode will activate,
and the internal battery voltage and MIDI circuitry will be checked automatically.
(2) In this mode, the switches have the following functions:
[WRITE] :Press the [WRITE] button to start checking each item.
[MODEA] :When [MODEA] is pressed, the test moves ahead to the next item
to be checked.
[MODEY] *. When [MODEV] is pressed, the test moves back to the previous item
to be checked.
11

<1. INTERNAL BATTERY CHECK >
(1) When the test node is activated, the voltage of the internal battery is
checked automatically.
(2) When an error is found, all LEDs on the panel blink, except PEAK.
The display will indicate the error details as below.
When the battery is low,
(—if~ Ii—
i
and £_/ wii| appear alternately.
When the battery voltage is high or no battery is loaded,
L[- LJ
7'and '''will appear alternately.
(3)
When this check ends normally, the test function automatically moves on
to the next item to be checked.
<2. MIDI CIRCUITRY CHECK >
(1) When the above check ends normally, the test function automatically checks
the MIDI circuitry.
(2) When an error is found, all LEDs on the panel blink, except PEAK.
The display will indicate the error details as below.
ndand Er~ will appear alternately.
(3)
When this check ends normally, the test function automatically moves on
to the next item to be checked.
<3. CPU CHECK >
(1) When all the above checks end normally, the display will indicate whether the CPU
mounted on the main board is for GTR or BASS. Confirm which it is.
For A4GTR
or
For A4BASS
EE
(2) When the above display has appeared for 0.5 seconds, the test function moves on
to the next check item.
12

<4. SWITCH AND LED CHECK >
(1) This test item covers the switches and LEDs.
(2) Press each of the switches in the order below to confirm that the corresponding
LED lights up.
DISPLAY
For A4 GTR
SW LED
For A4 BASS
SW LED
Pl-1 [1 COMPRESSOR] <1 COMPRESSOR> [1 COMP-DYNA EX] <1 COMP-DYNA EX>
PI—
2
[2 DIST/OD] <2 DIST/OD> [2 6BAND EQ] <2 6BAND EQ>
PI—
3
[3 3BAND EQ] <3 3BAND EQ> [3 SYNTH BASS] <3 SYNTH BASS>
PI—
4
[4 PITCH-DELAY] <4 PITCH -DELAY> [4 DELAY] <4 DELAY>
PI—
5
[5 CHORUS/FLANGER] <5 CH0RUS/FLANGER>[5 CHORUS/FLANGER] <5 CHORUS/FLANGER:
P1—6 [6 REVERB] <6 REVERB> [6 REVERB] <6 REVERB>
Pl-7 [BYPASS-TUNE] <BYPASS-TUNE> [BYPASS -TUNE] <BYPASS-TUNE>
PI—
8
[MODEY] <[!]> [MODEY] <[1]>
PI—
9
[MODEY] <[2]> [MODEY] <[2]>
Pl-10 [MODEY] <[3]> [MODEY] <[3]>
Pl-11 [MODEY] <[4]> [MODEY] <[4]>
PI— 12 [MODEA] <[ ]> [MODEA] <[ ]>
PI— 13 [MODEA] <[5]> [MODEA] <[5]>
PI— 14 [MODEA] <[6]> [MODEA] <[6]>
PI— 15 [MODEA] <[7]> [MODEA] <[7]>
Pl-16 [USER/PRESET] <USER> [USER/PRESET] <USER>
Pl-17 [WRITE] <-50> [WRITE] <-50>
PI— 18 [WRITE] <-50-0> [WRITE] <-50-0>
PI— 19 [WRITE] <0> (Green) [WRITE] <0> (Green)
PI -20 [WRITE] <0-+50> [WRITE] <0-+50>
PI—21 [WRITE] <+50> [WRITE] <+50>
PI -22 [PROG EDIT] [PROG] [PROG EDIT] [PROG]
PI -23 [BANK UP] [EDIT] [BANK UP] [EDIT]
(3) When [WRITE] is pressed, the test function checks whether the panel display
(7-segment LEDs) lights up in the sequence shown below.
SWITCH MAT RIX FOR A4 GTR
SWLO(POO) SWLl(POl) SWL2(P02) SWL3(P03)
SWD0(P04) USER
/PRESET
WRITE PROG/EDIT
BYP/TUN
BANK UP
SWDKP05) CH/FL
PEDAL
REVERB
PEDAL
PEDAL
PIT/DLY
SWD2(P06) DIST/OD
PEDAL
3BAND EQ
PEDAL
PEDAL
COMP
SWD3(P07) MODE UP MODE DOWN PEDAL
13

LED MATRIX FOR A4 GTR
HEBHITEM
mssBMwniM
WSfflM LINE4
(P73)
LINE5
(P50)
LEDKP40) IMJ3
mdp DP BYP/TUN
PEDAL
3BAND EQ
MODE
LED2CP41) TUNE
+1
eECOMP
PEDAL
UTILITY
MODE
LED3CP42) TUNE
0
dDDIST/OD
PEDAL REVERB
MODE
LED4CP43) TUNE
-1 gG3BAND EQ
PEDAL
CH/FL
MODE
LED5CP44) aAPIT/DLY2
MODE
LED6CP45) USER fFPIT/DLY
PEDAL
COMP
MODE
LED7CP46) PROG cCREVERB
PEDAL
DIST/OD
MODE
LED8CP47) ra bBCH/FL
PEDAL
PIT/DLY1
MODE
*LINE2 and LINE3 are the ports for the 7-segraent LEDs,
aA
dp DP
(4) When this check ends, press [WRITE] to proceed to the next check.
<5. PARAMETER KNOB CHECK >
(1) Here, the parameter knobs (A~F) on the panel and the volume pedal functions are
checked.
(2) First, when the knob is turned fully to the right (for the volume pedal,
when the pedal is pressed back as far as possible), this check confirms whether
the corresponding LED changes from ablinking state to asteady-lit state.
(3) Next, when the knob is turned fully to the left (for the volume pedal,
when the pedal is pressed forward as far as possible), this check confirms
whether the corresponding LED goes out.
(4) The check proceeds, one by one, in sequence from knob A.
(5) The table below shows the knobs and their corresponding LEDs.
14

A4GTR A4BASS
DISPLAY VR LED 1LED CPU PORT
P2-l,2 (A) <1 COMPRESSOR> <1 COMP-DYNA EX> AN2
P2-3,4 (B) <2 D1ST/0D> <2 6BAND EQ> AN3
P2-5,6 (0 <3 3BAND EQ> <3 SYNTH BASS> AN4
P2-7.8 (D) <4 PITCH* DELAY> <4 DELAY> AN5
P2-9, 10 (E) <5 CHORUS/FLANGER> <5 CHORUS/FLANGER> AN6
P2-11, 12 (F) <6 REVERB> <6 REVERB> AN7
P2-13.14 V. PEDAL <BYPASS*TUNE> <BYPASS-TUNE> AN1
(6) When all knobs have been checked, press [WRITE] to proceed to the next check item.
<6. CHECK OF EXT. CTRL OUT JACKS >
(1) This test item confirms whether the EXT. CTRL OUT 1and 2jacks are ON or OFF.
The EXT. CTRL OUT 1jack and the synthesizer’s damper jack are connected
by apatch cord. To check EXT. CTRL OUT 2, reconnect the patch cord.
(2) Confirm that the damper effect appears in the connected synthesizer
when EXT. CTRL OUT is ON. Also, confirm that the damper effect disappears
in the connected synthesizer when the EXT. CTRL OUT is OFF.
NOTE: This result will appear in reverse with some synthesizers because of
the setting of the damper polarity.
(3) Press [WRITE] to check the jacks in the order shown below.
DISPLAY A4 GTR(B) SYNTHESIZER
P3-1
P3-2
P3-3
P3-4
EXT. CTRL 0UT1 ON
EXT. CTRL 0UT1 OFF
EXT. CTRL 0UT2 ON
EXT. CTRL 0UT2 OFF
DAMPER ON
DAMPER OFF
DAMPER ON
DAMPER OFF
(3) When the checks are completed, press [WRITE] to proceed to the next item
to be checked.

<7. DSP CHECK >
(1) Here, the main board’s DSPs (IC10, IC11) and D_RAM (IC15, IC16) are checked.
(2) Connect the oscilloscope to the rear panel OUTPUT, and turn the OUTPUT volume
to MAX.
(3) Press [WRITE], and the check will proceed as shown in the table below.
Confirm that the waveform is the same as that shown in the figure.
DISPLAY A4 GTR(B) OUTPUT when no good
P4-1 DSP (KLM-1597 ICll)test OUT LCheck IC11 and analog circuit.
P4-2 DSP (KLM-1597 ICll)test OUT RCheck ICl 1and analog circuit.
P4-3 DRAM(KLM-1597 1C15, 16)test OUT LCheck IC11, IC15 and IC16.
P4-4 DSP (KLM-1597 IC10)test OUT LCheck IC10 and 1C11.
P4-5 DSP(KLM-1597 IC10)test OUT RCheck IC10 and IC11.
Figure 1
(4)
When the checks are completed, press [WRITE] to proceed to the next check item.
<8. TUNER FUNCTION CHECK >
(1) Here the TUNER function is checked.
Connect the rear panel INPUT jack to the oscillator.
(2) Set the INPUT volume and OUTPUT volume on the panel to MAX.
(3) Input ashort wave 27.5Hz/10mVp-p to the INPUT jack and confirm that
the TUNER LED 0(green) on the panel lights up.
(4) Input ashort wave 2093.005003Hz/10mVp-p to the INPUT jack and confirm that
the TUNER LED 0(green) on the panel lights up.
A4 GTR(B) TUNER Function
27.5Hz /10mVp-p
2093. 005003Hz/10mVp-p
TUNER <0> lit
TUNER <0> lit
(5)
When this check is completed, press [MODEA] to proceed to the next item
to be checked.
16

<9. PEAK LED CHECK >
(1) This test item checks the operation of the PEAK LED and its light-up status.
(2) Set the A4’s INPUT volume and OUTPUT volume to MAX.
(3) Input asine wave lkHz/-10dBm to the INPUT jack and confirm that the PEAK LED
lights red.
(4) Input asine wave lkHz/-14dBm to the INPUT jack and confirm that the PEAK LED
lights orange.
(5) Input asine wave IkHz/-50dBm to the INPUT jack and confirm that the PEAK LED
1ights green.
(6) Input asine wave lkHz/-70dBm to the INPUT jack and confirm that the PEAK LED
goes out.
INPUT SIGNAL PEAK LED
lkHz/-10dBm
lkHz/-14dBm
lkHz/-50dBm
lkHz/-70dBm
<PEAK> lights red
<PEAK> lights orange
<PEAK> lights green
<PEAK> goes out
*The check items that follow the PEAK LED check are for tests carried out
at the factory prior to shipment, and therefore are not covered here.
<10. TEST MODE COMPLETION AND DATA LOADING >
(1) Note that there are two methods of ending the test mode.
One method ends the mode without initializing the A4’s data.
The other method involves loading the preload data into the A4
and then ending the test.
(2) Press [MODEA] six times. As the check items move forward,
confirm that all LEDs except PEAK blink.
<Ending the test mode without initializing the A4’s data >
(3a) Press [MODEA]. The test mode will be ended without initializing the A4’s data.
<Ending the test mode by loading the preload data >
(3b) Press [WRITE]. The Preload data will be loaded into the A4
and the test mode will end.
(4) On returning to the normal mode, press [PROG EDIT] to confirm that the preloading
has been performed correctly. Confirm that the A4 GTR LEDs [2- DIST/OD],
[4: PITCH. DELAY] and [5: CHORUS/FLANGER] are lit, or that the A4 BASS LEDs
[1 :COMP. DYNA EX] and [2: 6BAND EQ] are lit.
17

8. REFERENCE DATA
MB89710A (CPU)
PIN ASSIGNMENT
m
P47
P70
P71
P72
P73
P74
ran
P50
P51
P52
P53
SCUT
SIM
P58
P57
AVao
AVR
AYse
AND
AN1
AN2
AN3
AN4
AN5
ANB
ANT
rnwr
MOO
xo
XI
Vas
CL 3^S3
cr S3
u13
E13
CE 13
CT S3
HS3
CE S3
E13
CE m
ES3
mS3
CE S3
ES3
ES3
E13
E13
E13
E13
E13
EE S3
E13
E13
E23
E3D
ES3
El SI
EE S3
BE 33
ES3
El S3
EE S3
Y«o
P45
P44
P43
P42
P4
1
PJD
P34
P33
P32
P3I
PSD
P22
P2I
P2D
PIT
PI 5
P15
P14
PIS
P12
PH
PIO
POT
POD
P05
P04
P03
PQ2
POI
POO
R5T
MB89710 (CPU)
PIN FUNCTION
PIN NAME I/O FUNCTION
P00-P07 I/O I/O PORT 0(SCAN FOR PANEL SWs )
P10-P17 I/O I/O PORT 1(DATA BUS FOR DSP )
XO ICRYSTAL OSC INPUT
XI 0CRYSTAL OSC OUTPUT
MOD IMODE SELECT INPUT
RES IRESET SIGNAL INPUT (LOW LEVEL ACTIVE )
START ISTART SIGNAL INPUT (LOW LEVEL ACTIVE )
NMI INON MASKABLE INTERRUPT INPUT
P20-P22 I/O I/O PORT 2(CHIP SELECT FOR DSPs )
P30-P37 I/O I/O PORT 3(CONTROL PORT FOR DSPs)
P40-P47 I/O I/O PORT 4(CONTROL PORT FOR LEDs )
VSS —GROUND (OV) INPUT
18

AK5349 (ADC)
INTERNAL BLOCK DIAGRAM
ICLK APD NC NO OCLK CLK SCLK L/IY FSYNC
(23)(6)(8) ( 22 )(21 )(20)(15)(14 ) ( 17)
AK5349 (ADC)
PIN FUNCTION
PIN NAME I/O FUNCTION
AINL+ ILCHANNEL ANALOG SIGNAL INPUT (+)
AINL- ILCHANNEL ANALOG SIGNAL INPUT (-)
VREFIN IREFERENCE VOLTAGE INPUT
VA+ —POWER SUPPLY FOR ANALOG CIRCUIT (+5V )
AGND —GROUND FOR ANALOG CIRCUIT
APD 1ANALOG POWER DOWN ("H* LEVEL ACTIVE)
ACAL IANALOG CALIBRATION
NC INO CONNECTION
DCAL 0DIGITAL CALIBRATION
DPD IDIGITAL POWER DOWN
TST ITEST
CMODE ICLOCK MODE ”L”: CLK=256fs (12.288MHz fs=48KHz)
”H”: CLK=384fs (18.432MHz fs=48KHz)
SMODE IINTERFACE CLOCK I/O SELECT
”L”: SLAVE MODE (L/R. SCLK &FSYNC*. INPUT )
”H”: MASTER MODE (L/R. SCLK &FSYNC: OUTPUT )
L/R I/O L/R CLOCK SLAVE MODE: fs CLOCK INPUT
MASTER MODE: fs CLOCK OUTPUT
SCLK I/O SERIAL DATA CLOCK SLAVE MODE: fs CLOCK INPUT
MASTER MODE: fs CLOCK OUTPUT
SDATA 0SERIAL DATA OUTPUT
FSYNC I/O FRAME SYNCHRONIZED CLOCK SLAVE MODE: CLOCK INPUT
MASTER MODE: CLOCK OUTPUT
VD+ —POWER SUPPLY FOR DIGITAL CIRCUIT (+5V )
DGND —GROUND FOR DIGITAL CIRCUIT
CLK IMASTER CLOCK INPUT CMODE=”H”: 384fs
CMODE=”L”: 256fs
OCLK 0128fs CLOCK OUTPUT
NC —NO CONNECTION
ICLK I128fs CLOCK INPUT
VL+ —POWER SUPPLY FOR LOGIC CIRCUIT (+5V )
LGND —GROUND FOR LOGIC CIRCUIT
VREF 0REFERENCE VOLTAGE OUTPUT 2.56V (VA+ =+5V )
AINR+ IRCHANNEL ANALOG SIGNAL INPUT (-)
RCHANNEL ANALOG SIGNAL INPUT (+>
19