Korg MONOPOLY POLYSIX MS-20 User manual

MONOPHONIC SYNTHESIZER
SERVICE MANUAL
CONTENTS
1. SPECIFICATIONS 2
2. STRUCTURAL DIAGRAM 3
3. CIRCUIT DIAGRAM (1) 4
CIRCUIT DIAGRAM (2) 5
4. FRONT VIEW OF PRINTED CIRCUIT BOARD
KLM-128C 6
KLM-127 7
5. PARTS LIST (Mechanical parts not listed) 8
6. BLOCK DIAGRAM 9
7. ADJUSTMENT PROCEDURE 10
KEia EL.ECTRONIC LABORATORY CORPORATtOIM
TOKYO/«JAPAN
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KORG MS-20
1. SPECIFICATIONS
<CONTROL SECTION >
t. Keyboard *C^C 37 kays (Socwvas)
2. Voltage controtfed •Scale (32'. b\ 4'> (6
o&citlaior 1ociaves, +canL -cent)
•Wave rofm (At K*Pw {nj
nj white noise) (4 modes]
•Pulse widtin adjust i:11
3. V.C.0-2 •Scale (W, &\ 4\ 20 (6 ociaves.
+ceni, -cant)
•Wave tofm (K,PL .ring
riKxJuietor) (4 modes)
•Pitch (±1 OCTAVES)
4, rnasier •MastaMuna (±100 cent)
control •Portamento (max. 00 sac)
•^Frequency modulatk>n inieruity
by MG/T. EXT (+5V)
•Frequency moduletior» intensify
by EG1/EXT( +5V)
5, V,C-0. mixer •V.C^O -1 level
•v.c,0.-2 level
6Voltage coi^trolled
high pass filter
7. Voliage controlled
low pass liller
8, Envelope
generator 1
9. Envelope
generalor 2
10. Modulaiion
generalor
1UManual controller
12. P. Swilchand
volume
13. Indicalor
•Cutolf Ireqyency
(50H2-15.000HI)
*Peak(llel'^seirOSC)
•Cuiod frequency modulation in-
tensity by MG/T.EXT
(^5V -+SV)
•Culofl frequency modulaiion in-
tensity by EG2/EXT
(-SV +5V)
•Cutoff frequency
(SOHi- 15.000HI)
•Peak (flat ^selfOSC)
•Cutoff frequency modulation in-
tensity by MG/ThEXT
(-5V- +5V)
•Cutoff frequency moduteiion in-
tensify by EG2/EXT
C-5V -- 45V)
•Defay time fiOsec)
•Attack lime [10 sec)
•Release time (10 sec)
•Hold lime [20 sec)
•Attack lime [10 sec)
•Decay lime (10 sec)
•Sustain level [0 --5V)
•Release time (10sec)
•VVsva form (iV A/I .
in -ru -LTl)
•Frequency (l:l1:80)
•Control wheel (center click)
(0.1Hz- 20Hj)
•Momentary switch
•Volume
•LED (KBD trigger, MG rale)
<EXTERNAL SIGNAL PROCESSOR>
1. Conirol seclion
2. Input and output
3. Indicator (LEO)
•Input signal levet (QdB max.)
•Low col Irequancy
[50 -2.500Hz)
•High cut frequency
(100 -5.000Hz)
•CV adjust
•Threshold level
•Signal In (auto pad system)
(1.0 -+ 14.0V)
•Amplifier Out
•Band pass filiered Out
•CV Out(F-V) (0 -+&.4V)
•£NVOut(0- +5V)
•Trig Out (+SV”Lgm})
•Peak indicaiof
•Trigger indicator
<PATCH PANEL >
1, Keyboard
2. VCO
3. VCF
4. VCO +VCF
5. VCA
6. EG
7. MG
•Keyboard caniroi voltage output
(exponeniial) (Q- +SV)
•Keyboard nigger output
(+5V “toNo)
•VCO-l +VCO-2 control
voUege input [linear response)
(0-+8V)
•VCO-2 control voflage input
(iinear response) (0 —8V)
•VCO’1 +VCO-2 external
frequerKy control input
(OCT/V)( +SV -SV)
•External signal input
(3Vp-pmax.)
•External HP liHer cutoff
frequency conirol input
(20CT/V)(-SV- +5V)
•External LP filter cutoff
frequency control Input
(20CT/V)( -5V- +SV)
•Total external modulation Input
(T.ext)(-6-+5V)
•External initial gain control Inpul
(0-+SVJ
•EG 1envelope signal normal
output (-SV —cr OV)
•EG 1envelope signal reverae
output t+5Vz:i—r::::0V)
•EG 1+EG 2trigger inpul
i”^C3M3)
•EG 1trigger input [“Lgmj )
•EG 2envelope signal reverse
output (A^,^ f-OV)
•Triangle oulpul [fs.^ /\ ^^)
(SVp-p-K-OV)
•Rectangle ouiput (tn^ fU ^
LJI)
(in::^,)
8. Noise generator •Pink noise ouiput (5Vp-p ±20)
•White noise output (SVp-p ±20)
9. Sample and hold •Clock trigger input (~Lqw)
•Sample signal input (5Vp-p
max.)
•S/H output (5Vp-p max.)
10. Modulation VCA •Control vpliago input (0- +5V)
•Signal input {-SV— +SV)
•Signal ouipui( ^-SV— +SV)
11^ Manual controller Conirol wheel ouiput
(-5V ^OV- +5V)
•Momentary switch output
12. Signal out
13. Headphones
•Signal outpul (2Vp-p output in-
pedance 3.5kn)
•Head phones output ((8P]
12dm wans 5.6)
14. Power consumption^ 10 watts
15. Dimensions
16. Weight
17. Accessories
18. Options
•SS9[WJ X309(D) X249(H) mm
•7,7 kgs
•Patch cord, connection cord
(35 cm X2. 3mX1
)
•Stand, hard case, fool pedal
(MS01)
•Junclion box [MS -02]

KORG MS-20
3. CIRCUIT DIAGRAM (1)
VOC -JI-2
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(Toisl
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KORG MS-20
CIRCUIT DIAGRAM (2)
KLM-128
*41
2TK
KLM-129

KORG MS-20
4. FRONT VIEW OF PRINTED CIRCUIT BOARD KLI
VOC I
KBD FOLLOWER FREQ
MOD TRIG
-127
FILTER LP-FILTER VGA POWER SUPPLY EG 2

PHOmE
AHP.

KORG MS-20
5. PARTS LIST
(Mechanical parts no1 listed)
•CARBON RESISTORS •POLYSTYRENE CAPACITORS •ROTARY VARIABLE [
not Ifsted 50V-3000pF X1RESISTORS
50V-6200pF X110KB X4
•METAL FfLM RESISTORS lOOKA Xa
1/4W 1% tOOJJ X 2 •POLYPROPPYLENE 100KA X4
1/4W 1% 403ft Xie CAPACITORS 1MB X2
I/4W 1% 427ft X22 200V-0.22mF X12MA X6
1/4W 1% Ikft X3IMA X2
1/4W X3•TRANSISTORS Pmtfld 10KA X1
1/4W 1% 2.94kft X12SA-564(S) X4Prmted lOKB X1
V4W 1%4.27kft X12SC-945{L>K X1Printed 1MB X1
V4W 1% lOkft X1(spectei selected) Primed 4- ganged 100KC X1
1/4W 15kfl X12SC-1583G X224^ 10KB X1
1/4W 1%20kII X22SC-1685S X13 Center click-stop 10KB X1
1/4W 1%S1.9kft X 17 2SC-644R K1
1/4W 1% tOOkft X23 •ROTARY SWITCH
1/4W 1% nOkft X1•FET SRM-1034 l-lSrem X 4
X\2SK-30(O) X 4
2SK-30(GR) X 4 1•KEYBOARD
•SOLID RESISTORS ESK-431 37 key
t/4W 10% lOMO X7•DIODES
IS- 1555 X33 •TERMINAL LUG BOARD
•MYLAR CAPACITORS 2L4P X1
nol listed •LED
GD4-203RD X 4 •PUSH SWITCH
•STYROLCAPACITORS MS-1 02 X1
50V-12000pF X1•PHOTOCOUPLER
HTV-PS73-G3S-201S X1•CONNECTORS
•CERAMIC CAPACITORS 1T)3P X8
SOV^SOpF X1•IC 4P X2
50V-22pF X1>iPC-4558C X17 5P X2
50V-100pF X5081 X57P X1
5OV-2a0pF X 2 TL-(071) ^8P X2
50V-47pF X1(3140} S3P X3
25V-100000pF X 2 082 X1r* 5P X1
TL-(072} Female Connectors
•tantalum capacitors (3140) 3P X10
16V-3.3mF X1MC- 14007 X24P X2
16V-6.SmF X 2 MC-140&9B X25P X3
mPD4011C X17P X2
•ELECTROLYTIC CAPACITORS mPC339C X1flP X2
16V-10jjF X 12 mPC14315 X1
16V-33mF X 2 mA79M15 X1
16V-100mF X 4 KORG3S X 2
50V- ImF X 6
25V-470*iF X1•SEMI-FIXED RESISTORS
25V- 10000m
F
X1SR19R(10kB) X6
16V-220*iF X1SRl9R(lODkB) X7

KORG MS-20
6. BLOCK DIAGRAM
MAX2VPP
SI6 0UT
PHONES
TRIG OUT
HRES LEVEL
CHECK POINT QKLMI27 ^)kLMI28 QKLMIZS

KORG MS-20
7. ADJUSTMENT PROCEDURE
7-1 Power supply check
1.Positive lippte.
Should be no more than 2mVp-p,
Set oscilloscope vertical gain at lOmV/cm end
check that power supply ripple is 2mV or less.
2. Negative ripple.
Same as positive, should be no more tharv
2mVp-pH
7-2. Pitch adjustment
1, VCO-1.
Perform adjustment with synthesizer controls at
"normal setting” (Scale =8, Waveform— fU .
Master Tune. Pitch, artd all other knobs at "0'%
See figure 1
.
a. Play C-4 (high C) on the keyboard and ad-
just the high Osernl -fixed screw until you obtain
the correct tuning as indicated by WT-10A
(connected lolheSIG OUT jack).
b. Play key C-1 and adjust the low ^semi’
fixed screw.
0
.
Repeat steps aand b as many times as
necessary until both are tuned to the correct
pitch.
d. Check the tuning of C*1, C-2, G-3, and G-4
on the WT-10A meter to make sure pitch devia-
tion is within ±2 cents for each.
e. Change the scale to 32\ 16", 8', and 4' and
check the tuning of all four Ckeys to make sure
that the pitch deviation of each Is within +10cents.
2. VCO-2.
Set the VCO-1 level at and the VCO-2 level
at '"10". Then follow the same procedure as for
VCO-1. by adjusting the high and low
semt'fixed screws.
7-3. KSDCV adjustment
Use a4-1/2 digital voltmeter to measure the K6D
CVOUT signal.
a. Measure output vottage first when you play
key C-4, then when you play key C-3. The output
voltage for C-3 should be exactly halt that for
C-4. Adjust the KBD CV high 0semi-tixed
screw as necessary so that C-3 produces half
the vottage of C-4.
b. Measure C-2 and then C-1 in the same way.
Adjust the KBD CV low 0semi-fixed screw as
necessary so that C-2 produces exactly half ihe
voltage ot C-4.
c. Repeat steps aand bas many times as
necessary until the output voltage of each of
C-1, C-2. C-3. and C-4 is exactly half that of the
next.
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WT-10A
DIGITAL
VOLTMETER
Fig. 1
7-4. VCF Fc adjustment
Ck>nnect afrequency counter to the PHONES jack
(since a high output level es needed tor measure-
ment). Set VCO-1 and VCO-2 level at "0^
1.
VCHPF
Refer to the settings shown in figure 2, Set the
LPF PEAK knob at "0'\ and the HPF PEAK knob
at "10”. Then adjust the Osemi-fixed screw as
necessary so that the HPF oscillation frequency
is 500Hz.
2.
VC LPF
Set HPF PEAK at ’0”. and LPF PEAK at ”10",
Then adjust the 6semi-fixed screw in the same
way as you did for the HPF.
FREQUENCY
COUNTER