Moog Micromoog 2090 Operating manual

TECHNICAL

SERVICE

MANUAL

for

MICROMOOG

and

MULTIMOOG

synthesizers

MICROMOOG

MODEL

2090

MULTIMOOG

MODEL

326A

James

Scott

•

BSEE

(Author)

MOOG

MUSIC

INC.

2500

Walden

Avenue

Buffalo.

N*w

York

14225

October.

1979

CONTENTS

SECTION

PAGE

NO.

Title

Page

Frontispiece

Contents

List

Illustrations

List

Tables.

INTRODUCTION.

1.1

ORGANIZATION

THE

MANUAL

1.2

GENERAL

SYSTEM

DESCRlP“ION

1.3

MODEL

MODIFICATIONS.

CIRCUIT

DESCRIPTION.

2.1

POWER

SUPPLY.

2.2

KEYBOARD

CIRCUIT.

2.2.1

Operation

(Cortrol

V/nlugo

Generation)

22.2

Operation

(Trigger

Generation)

2.3

CONTROL

VOLTAGE

SUMMEHS

AM)

DUAL

EXPONENTIAL

CURRENT

SOURCE

2.3.1

Oscillator

Control

Summing.

2.3.2

Filter

Control

Summing.

2.3.3

Dual

Exponential

Current

Source

2.4

OSCILLATOR.

WAVESHAPER

AND

DOUBLER.

4.1

Oscillator.

4.2

Waveshaper.

2.4.3

Doubler.

2.5

VOLTAGE

CONTROLLED

IQWPASS

FILTER

2.6

VOLTAGE

CONTROLLED

AMPLIFIER.

2.7

DUAL

CONTOUR

GENEHATOP.

MODULATION.

2.9

NOISE

SOURCE

SAMPLE

AND

HOLD.

2.9.1

Noise

Source.

2.9.2

Sample

and

Hold.

2.10

MISCELLANEOUSOFF

BOARD

COMPONENTS

Top

Boord

Tandem

Board

2-1

2-2

2-3

2-5

2-7

2-8

2-9

2-11

2-13

2-15

2-17

DISASSEMBLY

PROCEDURES

...

3.1

OPENING

THE

SYNTHESIZER

KEYBOARD

REMOVAL.

3.3

MAIN

BOARD

REMOVAL

....

3.4

LEFT

HAND

CONTROLLER

(LHC

3-1

3-10

TUNING

AND

ADJUSTMENT

PROCEDURES.

4.1

EXTERNAL

AND

TfcHNAL

ADJUSTMENTS.

4.2

EXTERNALLY

ACCESSIBLE

ADJUSTMENTS.

4.2.1

Oscillator

Tuning.

4.2

1.1

Oscillator

Range.

4.2

1.2

Oscillator

Scale.

4.2.1.3

Oscillator

High

Frequency

Compensation

4.2.1.4

OsciMotor

Octavo

Stop.

4-1

4-2

CONTENTS

(Continuod)

SECTION

4.3

FILTER

TUMING.

4.3.1

Emphasis.

4.3.2

Filler

Scalo.

4.3.3

Filter

High

Frequency

Compensation.

4.3.4

Filter

Octave

Step.

4.4

OTHER

ADJUSTMENTS..

4.4.1

VCA

Balance.

4.4.2

Trill

Trim.

4.4.3

Ribbon

Centering.

4.5

INTERNALLY

ACCESSIBLE

ADJUSTMENTS.

4.6.1

16V

ADJ.

4.5.2

Current

Source

Chip

Temperature.

Filter

Balance

Filter

Rang©

4.6

MULTIMOOG

OSCILLATOR

TUNING

PROCEDURE

4.6.1

Oscillator

Temperature

Adjustment

4.6.2

Oscillator

"A"

Tuning.

4.6.3

Interval

Tuning

Adjustment.

TROUBLESHOOTING

GUIDE.

5.1

SOUND

CHAIN.

5.2

PITCH

DRIFT

AND

TUNING.

b.2.1

Oscillator

Drift.

6.2.2

scillator

and

Filter.

5.3

KEYBOARD.

5.3.1

leaning

Key

Contacts.

REPLACEMENT

PARTS

LIST.

MOTE:

This

lection

also

contains

Multimoog

circuit

description

and

schematic

diagrams

PAGE

NO.

LIST

ILLUSTRATIONS

FIGURE

1-1

1-2

1-3

2-2

2-3

2-4

2-5

2-6

2-7

2-8

2-10

3-2

3-5

3-7

3-8

3-10

3-11

3-12

3-13

4-2

4-3

6-1

6-2

Rcor

Panel,

Early

Version.

Rear

Panel.

Latest

Version.

Control

Panel,

Early

Version.

Control

Panel,

Latest

Version.

Simplified

Regulator

Schematic

Keyboard

Control

Voltage

Generation.

Equivalent

Keyboard

String.

Equivalent

Amp

O/P

Circuit.

Simplified

Oscillator

Circuit.

Waveshaper

Output

Shape

Versus

Waveshape

Control

Voltage.

VCF

Frequency

Response

Curves

tor

Zero

and

Full

Emphasis.

Equivalent

Filter

Ladder

rcuit..

•

Envelope

Shape

(Either

Section)

Timing

Capacitor

C705

„706

Loudness

Limiting.

Removing

Case

from

Base.

Unplugging

Audio

Output

Connector.

Unlocking

Cable

Clomp..

Base

Assembly.

Installation

Grommet

Strip.

Removing

Ivor

os.

Levelling

Key.

Keyboard

Mounting.

Servicing

Switch

Contacts.

Keyspring

Replacement.

Knob

Removal.

Board

Removal.

Board

Service

Position.

Left

Hand

Controller

Removal.

Left

Hand

Controller

Assembly,

Part

No.

93-603

Position

for

Making

Externally

Accessible

Adjustments.

Oscillator

Tuning

Sound

Chart.

Filter

Tuning

Sound

Chart.

VCA

Balance

Trill

Trim

Sound

Chart.

Sound

Chain

Check

Micromoog

Block

Diagram.

Micromoog

Interconnect

Harness

Assembly.

Micromoog

Schematic

Diagram.

PAGE

NO.

1-2

2-1

2-3

2-4

2-8

2-10

2-11

2-12

2-14

3-2

3-3

3-4

3-6

3-7

3-8

6-5

6-7

LIST

TABLES

TABLE

5-1

Sound

Chain

Troubleshooting

Guide.

.....

Oscillator

and

Filter

Troubleshooting

Guide

5-3

Keyboard

Troubleshooting

Guide.

5-4

Pots

and

Switches

Troubleshooting

Guide..

5-5

Control

Circuits

Troubleshoot

Guide

5-6

Power

Supply

Troubleshooting

Guide

....

5-7

Noise,

Etc.

Troubleshooting

PAGE

NO.

5-1

5-4

5-6

5-7

5-9

5-10

SECTION

INTRODUCTION

This

manual

provides

servicing

and

parts

infor¬

mation

for

tho

Micromoog/Multimoog

Synthesizers.

ORGANIZATION

THE

MANUAL

The

manual

divided

into

sections.

Section

provides

general

system

description

and

model

modifications;

Section

describes

the

circuit.

Section

gives

step-by-step

procedures

for

disassembly

the

keyboard,

main

hoard

and

the

left

hand

controller.

Section

describes

the

tuning

and

the

external

and

internal

adjustment

procedures.

Section

contains

the

troubleshooting

guide.

facilitate

ordering

replacement

parts,

see

.Section

GENERAL

SYSTEM

DESCRIPTION

tSee

Block

Diagram

—

Figure

6-1)

The

Synthesizers

consist

several

circuit

blocks.

The

POWER

SUPPLY

converts

line

voltage

into

precisely

regulated

±15

volts

operate

all

other

Micromoog

circuits.

single

VOLTAGE

CON¬

TROLLED

TONE

OSCILLATOR

(VCO)

generates

the

audio

frequency

waveforms

that

serve

the

source

pitched

soundn.

The

wuveshaped

output

this

oscillator

passes

through

the

VOLTAGE

CONTROLLED

LOWPASS

FILTER

(VCF)

which

strongly

modifies

the

timbre

the

oscillator

tone.

Tho

NOISE

SOURCE

produces

pitchloa;

hitting

sound

that

also

may

fed

into

the

filter.

The

outpu:

the

VCF

pases

through

the

VOLTAGE

CON¬

TROLLED

AMPLIFIER

(VCA)

the

Instrument

audio

output.

The*

gain

the

VCA

dynamically

shaped

during

note

one

section

the

DUAL

CONTOUR

GENERATOR.

The

VCA

and

contour

generator

operating

together

constitute

loudness

ARTICULATOR

The

other

section

the

DUAL

CONTOUR

GENERATOR

dynamically

shapes

the

timbre

the

VCF

during

note.

The

contour

generator

action

initiated

trigger

generated

within

the

KEYBOARD

each

time

key

depressed

The

KEYBOARD

also

generates

control

voltage

that

increases

successively

higher

keys

are

depressed

This

control

voltage

establishes

the

VCO

pitch

and

the

same

time

causes

the

VCF

track

the

VCO

maintain

constant

timbre.

The

MODULATION

OSCILLATOR

generates

subaudio

waveforms

used

for

control

(not

audio)

purposes.

This

oscillator

also

triggers

the

SAMPLE

AND

HOLD

which

samples

the

noise

circuit

yield

control

voltage

that

randomly

changes

levels

tempo

sot

the

RATE

control.

The

source

modulation

set

the

SOURCE

switch

and

the

circuit

will

modulate

chosen

the

ROUTING

switch.

The

MODULATION

AMOUNT

wheel

controls

the

level

sent

the

selected

circuit

The

Micromoog

provides

power

operate

auxiliary

equipment.

Through

the

rear

panel

the

Micromoog

interfaces

with

external

equipment

such

auxiliary

controllers,

other

synthesizers,

modular

equipment

and

other

musical

instruments.

1.3

MODEL

MODIFICATIONS

This

manual

refers

the

current

production

model

July

1976

Serial

Number

3300

and

above.

Since

the

Micromoog

was

introduced

the

music

world,

several

major

and

numerous

minor

improvements

have

been

incorporated.

Some

the

modifications

are

discussed

and

illustrated

tho

following:

July

1976,

the

keyboard

was

modified.

functions

identically

and

interchangeable

with

oirlior

model::.

Tho

discroto

rosUtorB

and

vortical

Board

have

been

replaced

resistor

packs

and

horizontal

Board.

direct

audio

output

cable

has

been

provided

eliminate

slight,

bleed

thru.

The

cable

now

available

field

retrofit

kit

small

rear

panel

Board

and

control

pot

(R261)

has

been

added

provide

variable

keyboard

output

control

voltage.

See

Figures

1-1

and

October

1975,

the

nomenclature

the

main

control

panel.

Serial

Number

1500

and

above,

was

revised

with

functional

changes.

See

Figures

1-3

and

14.

1-1

FIGURE

REAR

PANEL,

EARLY

VERSION

FIGURE

1-2

REAR

PANEL,

LATEST

VERSION

FIGURE

CONTROL

PANEL,

EARLY

VERSION

NEW

NOMENCLATURE

FIGURE

CONTROL

PANEL,

TEST

VERSION

1-2

SECTION

CIRCUIT

DESCRIPTION

2.1

POWER

SUPPLY

115

VAC.

IC101

has

been

observed

survive

the

1/4

second

overvoltage

that

occurs

its

inputs

The

supply

druws

160

from

115

VAC

such

ar.

instance.

input

(or

from

230

VAC

input)

when

the

15V

and

15V

outputs

are

200

each.

and

decouple

RKI

that

may

riding

the

steps

the

input

down

VAC

cemer-

lino.

SW1

connects

the

primaries

parallel

for

tapped

The

diode

bridge

CR101-CR104

rectifies

the

115V

operation

and

series

for

230V

operation.

roughly

VDC.

normal

full

load

and

are

parallel

for

115

VAC

operation

(250

150

(Micromoog

with

1125

Sample

and

Hold

blowout

point)

and

series

for

230

VAC

operation

plugged

into

back),

C101

and

C102

provide

sufficient

(125

blowout

point).

The

fuses

protect

against

filtering

keep

the

raw

ripple

around

2Vp-p.

Dual

fire

hazard

should

short

occur

the

secondary

tracking

regulator

IC101

operates

with

external

pass

Tl.

They

will

not

blow

the

regulator

outputs

short

transistors

Q101

and

Q102.

These

transistors

drop

the

out.

(The

legulator

will

current

limit

instead.)

They

ruw

voltages

DC.

C103

and

C104

stabilize

will

blow

i:'

230

VAC

applied

and

SW1

set

for

the

regulator

against

high

frequency

oscillation.

FIGURE

2-1

SIMPLIFIED

REGULA

TOR

SCHEMA

TIC

2-1

Since

ihe

base-emitter

drop

external

pass

transistor

Q101

about

0.6V,

R101

will

feed

about

(0.6V/47

ohm

12.5

mA)

into

IC101

which

than

sufficient

supply

the

required

operate

internal

chip

circuitry.

passes

the

balance

this

12.5

mA.

Q101

forms

PNP-NPN

Darlington

configuration

with

the

internal

pass

transistor

Qa.

Q101

passes

mosl

the

positive

current

and

therefore

dissipates

most

the

heat

allowing

IC101

run

cooler.

senses

♦

and

causes

the

internal

circuits

drive

maintain

the

output

very

procisoly

the

line

and

load

vary.

The

sense

input

provides

another

service;

reaches

250

mA,

the

drop

across

R103

will

rise

0.7V

and

Ihe

supply

will

into

the

current

limit

mode.

the

output

shorted

ground,

Q101

will

dissipate

several

times

normal

power.

However,

Q101

will

not

burn

out

matter

how

long

its

output

remains

shorted

due

the

attached

heat

sink.

The

negative

regulator

works

exactly

the

same

fashion

positive

regulator.

Here

are

some

important

specs:

Input

Voltage

Output

Accuracy

Lcng

Term

Output

Drift

Output

Load

Keg.

Output

Lin*

Reg

Output

NoUe

Output

Temp.

Stab.

Output

Current

Limb

Value

♦

30V

Max.

(-1SV

trimmed)

300mV(+

ur.trimmedi

♦

mV/1000

hours

typical

Max.

230

mA)

Max.

(SO

VAC

130

VAC

60Hz)

1.0

RMS

Max.

(100

LOO

kHz

B.W.i

0.016%/°C

Max.

250

C105

and

C104

are

solid

tantalum

types

effectively

filter

high

frequency

noise.

CR105

and

CR106

protect

the

regulator

against

accidental

con¬

nexion

supply

opposite

polarity.

RIOfi

sets

the

15V

supply

15.00V.

must

se.

accurately

since

the

reference

for

the

Keyboard

String,

Octave

Buffer,

Oscillator

Range

and

Chip

Tomporaturo.

The

15V

supply

new!

not

extremely

accurate

trim

provided

for

it.

still

must

precise

—

i.e.:

must

not

drift

noisy,especially

since

the

15V

supply

tracks

the

15V

supply.

Cl09

and

decouple

the

power

supply

lines

tho

main

Board

forestall

parasitic

oscillations

The

1468

regulator

ceramic

encapsulated

device

(non-hermetic

glass

frit

type)

rather

than

plastic

device.

The

use

plastic

package

would

result

chip

temperature

125°C

(not

necessarily

worst

case).This

dangerously

the

maximum

allowable

chip

temperature

150°.High

temperatures

cause

shortened

chip

life,

rapid

long-term

drift,

and

greater

thermal

(warm-up)

drift.

With

ceramic

encapsulation

the

chip

temperature

about

85°C

much

comfortable

figure.

2.2

KEYBOARD

CIRCUIT

Tho

KEYBOARD

CIRCUIT

produces

control

voltage

(to

determine

pitch)

that

increases

linearly

successively

higher

keys

are

depressed.

The

control

voltage

increases

from

0.00

volts

(lowest,

key)

tho

rate

one

volt

per

octave

(83.3

mV'semitone)

maximum

2.58V

(highest

key

2-1/2

octaves

above

F).

The

keyboard

has

low-note

priority.

the

performer

holds

down

several

keys

simultaneously,

the

lowest

key

determines

the

control

voltage.

The

GLIDE

control

allows

adjustment

the

control

voltage

transition

rate

from

0.3

msec

time

constant,

(effectively

instantaneous

pitch

change)

1.0

second

time

constant,

(effectively

several

seconds

before

the

pitch

catches

the

controlling

key

and

stops

changing).

The

Keyboard

possesses

memory

that

maintains

tho

control

voltage

precisely

the

level

the

output

the

instant

the

last

key

released.

2.2.1

OPERATION

(CONTROL

VOLTAGE

GENERATION!

(FIGURE

2-2)

IC202A

applies

constant

current

(set

833

R238)

the

keyboard

resistor

string.

The

1,0

end

the

string

remains

ground

potential

matter

how

many

how

few

keys

are

closed.

Note

that

the

I-R

drop

across

the

remainder

the

string

below

ihe

lowest

closed

contact

establishes

VOUT

applied

the

buss

than

one

contact

closes,

flows

onto

the

bus

the

highest

closure

and

returns

the

string

the

lowest

closure.

The

intervening

resistors

are

simply

shorted

out.

2-2

FIGURE

KEYBOARD

CONTROL

VOLTAGE

GENE

RATION

When

key

contact

closes,

holding

capacitor

C212

charges

(or

discharges)

tho

rate

set

R251

the

level

established

the

buss.

R250

sets

minimum

charging

time

constant

TCH

(min)

=0.22

1.5K

“

0.33

msec.

R250

decouples

the

kHz

pilot,

oscillator

signal

(spp

below)

from

the

control

voltage

C212.

R250

also

filters

key

contact

scrape

and

bounce

that

occurs

when

lower

contact

closes

while

upper

contact

being

held

closed.

When

all

keys

are

released,

further

charging

C2I2

possible

and

holds

the

last

instantaneous

value

control

voltage.

Dual

J-FET

Q201

conjunction

with

R252,

R253

and

IC204A

comprise

extremely

low

input

bias

current

unity

gain

buffer.

The

buffer

provides

substantial

control

voltage

output

drive

capability

while

draining

C212

less

than

200

rote.

MAX.MUN

mSCHAROE

NOTE

The

output

side

the

buffer

guards

the

input

side.

This

vastly

reduces

on-board

eakage

since

potential

equal

the

value

being

held

surrounds

tho

entire

holding

circuit.

C213

nnd

C214

decouple

RFI

pickup

the

main

Board.

C214

also

shunts

capacitive

audio

pickup

the

keyboard

control

voltage

output

line.

CR203

and

CR204

protect

Q201

and

1C204A

from

static

discharge

coming

via

J3.

R257

does

not

affect

the

output

li'vol

normally

(it.

inside

the

loop)

but

docs

allow

control

voltage

forced

into

for

testing

purposes,

for

introducing

external

control

voltages

override

the

keyboard

control.

22.2

OPERATION

ITRIGGER

GENERATION)

Since

the

keyboard

uses

single-buss

contact

scheme,

pilot,

signal

(generated

IC201)

must

injected

onto

the

buss

that

detection

contact

opening

and

closing

can

occur.

When

closure

occurs,

IC203

and

IC202B

amplify

and

detect

the

signal

and

develop

clean

trigger

output.

Oscillator

1C201

generates

the

kHz

triangular

signal.

kHz

lies

above

the

audio

range

which

reduces

the

chance

that

unwanted

signal

pickup

other

Micromoog

circuitry

will

audible.

The

3080

transconduclance

amplifier

was

chosen

IC201

because

has

very

fas:

slew

rate,

does

not

delay

coming

out

input

output

saturation

and

does

not

draw

current

slugs

from

the

supply

lines

while

slewing

while

saturated.

The

output

3080

bilateral

current

source

the

magnitude

which

given

by:

lOUT

0-02

pA/ni»

(

npu

[

OCT

(Mix.)

BIAS

bias)

R235

sets

IFUAS

(into

0.5

raa

which

keeps

the

total

package

dissipation

mW.

well

below

the

absolute

maximum

125

rrW.lOUTwill

tend

alternate

between

0.5

and

0.5

rnA,

2-3

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