Hammond L series User manual

SERVICE
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HO-735
HAMMOND ORGAN COMPAIW
DIVISION OF HAMMOND CORPORATION
11700 Copenhagen Court /Franklin Park, lUinois 6013]
[phone]

TABLE OF CONTENTS
Page
Introduction .iv
Specifications iv
SECTION I-How the Organ Operates
1-1 General 1-1
1—2 Tone Source 1—1
1—3 Motor and Power Switch 1—4
1—4 Tone Generator 1-4
1—5 Manuals 1—5
1—6 Harmonic Drawbars 1—7
1-7 Pedal Drawbar 1-7
1-8 Pedal Keyboard 1-7
1—9 Expression Pedal 1—7
1-10 Control Tabs 1-8
1-11 Preset Tabs 1-8
1-12 Vibrato Tabs .1-8
1—13 Reverberation Volume Soft Tabs 1—8
'1— 14 Percussion Control Tabs 1—8
1-15 L-IOOA Preset Percussion Unit 1-9
1-16 Selector Switch 1-9
1-17 Harmonic Busbar Switching and Reiteration Split ... 1-9
1—18 L— 100—1Six-Voice Percussion Feature .1—9
1—19 Location of Controls 1—9
1-20 Voicing 1-9^
1-21 Operation of Controls 1—9
1—22 External Equipment 1—1
1—23 Extension Speakers 1—1
1—24 External Sound Source 1-1
1—25 Earphones 1—1
SECTION II -Theory of Operation
2- 1General 2-1
2—2 Preamplifier 2—1
2-3 Vibrato Phase Shift Amplifier 2-1
2—4 Percussion Amplifier 2—2
2-5 Reverberation and Power Amplifier 2—2
2-6 Power Supply 2-3
2—7 L-IOOA Percusion Voicing Circuitry 2-3
2-8Mode Switch 2-3
2—9 Frequency Divider 2—4
2-10 Cymbal and Brush 2-4
2-11 Brush Keying 2-4
2—12 Cymbal Keying 2—4
2—13 Bmsh and Cymbal Amplification 2-4
2—14 Power Supply 2-4
2—15 L- 100-1 Six-Voice Percussion Circuitry 2-4
2-16 Power Supply 2-4
2-17 Push-Button Circuits 2-5
2-18 Lower Manual Keying Circuits 2—5
2-19 Pedal Keying Circuit ^2-5

SECTION III -Disassembly
3-1 General ,3-1
3-2 Access ,...3-1
3—3 Upper Manual Key 3—1
3—4 Lower Manual Key 3—1
3—5 Drawbar Contact Spring 3—1
3—6 Drawbar, Drawbar Knob, Drawbar Assembly 3—1
3-7 Upper Manual 3-2
3—8 Lower Manual 3—2
3—9 Generator 3—2
3-10 Motor 3-2
3-11 Pedal Keyboard 3-2
3—12 Swell Assembly 3—3
3-13 Tab 3-3
3-14 Pilot Light on Power Switch 3-3
3-15 L-IOOA Percussion Circuitry 3—3
3— 16 L— 100—1Six-Voice Percussion 3—3
SECTION IV -Practical Service Suggestions
4-1General 4-1
4—2 Organ Performance Check 4—1
4—3 Equipment Required 4—1
4-4 Procedure 4—1
4-5 Vibrato 4-2
4—6 L— 1OOA Percussion Performance Check 4—3
4—7 L- 100- 1Six-Voice Percussion Performance Check
and Troubleshooting 4—4
4-8 Output Level Adjustments 4-4
4-9 One Voice is Silent :4-4
4-10 Programmed Voice Does Not Speak 4-4
4— 1 1 All Percussion Voices Silent 4—4
4-12 Both Hiss Voices Silent 4-4
4—13 No Voice Response from Pedals 4—4
4—14 No Voice Response from Manual 4—4
4—15 No Percussion Output 4—4
4— 16 Troubleshooting 4—4
4-17 Organ Does Not Play 4-5
4—18 Key Does Not Play or Harmonic Missing 4—5
4-19 One Note is Weak 4-6
4—20 Percussion Notes Weak or Missing (L— 100) 4—6
4-21 Full Volume Pedal Cipher 4-6
4-22 Hum 4-6
4—23 Replacing Tubes 4—6
SECTION V-Diagrams
5— 1General 5—1
SECTION VI -Parts List
Index -L-100 Series 6-1
Index -L-200 Series 6-15

LIST OF ILLUSTRATIONS
Wigure Page
1-1. L-lOO Console, Front View 1-1
1—2. L— 100 Console, Rear View 1—2
1-3. Block Diagram, L- 100 Series 1-3
1—4, Typical Tone Generator 1—4
1—5. Magnet Locations on Tone Generator 1—4
1—6. Filter Locations and Frequency Terminations on
Generator Cover 1—5
1-7. Manual Wiring Chart 1-6
1—8. Drawbars &Control Tabs (Partial View) 1—7
1-9. Pedal Keyboard 1-8
1-10. L- 1OOA Preset Percussion Unit 1-10
1-11. L- 100- 1Six-Voice Percussion Controls 1-10
1—12. Earphone Adapter Circuit 1—11
4— 1. Vibrato Adjustment Waveform 4—2
5— 1. Schematic Diagram, L— 100 Organ with AO -41 Amplifier .... 5—2
5—2. Schematic Diagram, L— 100 Organ with AO—47 Amplifier .... 5—3
5—3. Schematic Diagram, L— 100 Organ with AO—47 Amplifier
and LDR Expression Control 5—4
5-4. Schematic Diagram, L-IOOA, L- 100-1 8l L- 100-2
Organ Consoles 5—5
5—5. Schematic Diagram and Parts Layout, L— lOOA Percussion Unit 5—6
5—6. Schematic Diagram and Parts Layout, L— 100— 1Six-Voice
Percussion 5—7
5—6A. Schematic Diagram and Parts Layout, L— 100— 1Six-Voice
Percussion, Early 1970 Production 5—8
5—7. Schematic Diagram, L— 100- 1Percussion Power Supply .... 5—9
5—8. Schematic Diagram &Parts Layout, Pedal Control Board .... 5—10
5-9 Wiring Diagram, L- 100 Organ 5-11
5-10. WiringDiagram, L- 100-1 and L- 100-2 Organs 5-12
5—11. Wiring Diagram, Control Panel, L-lOO Series 5—13
5— 12. Wiring Diagram, Control Panel, L- 100 Series Revised 5—14
5—13. Wiring Diagram, Percussion Unit, L—1 OOA 5—15
5—14. Wiring Diagram, Six-Voice Percussion, L— 100— 15—16
5-15. PartsLayoutAO-41 Vibrato Amplifier 5-17
5-16. PartsLayoutAO-47 (126-000023) Vibrato Amplifier 5-18
5-17. PartsLayout,AO-42 (117-000019) Percussion Amplifier .. 5-19
5-18. Parts Layout, AO-43 (126-000017) Power Amplifier 5-20
5-19. Power Amplifier Fuse Location (Canadian, 101—000130) .... 5—21

INTRODUCTION
This manual contains service information for L—100 Series organs. The series is comprised of the following
models: L-lOO
L-IOOA
L-100-1
L-100-2
L^200
The Model L—100 Hammond organ is acompletely self-contained console, requiring no external tone
cabinet. It has two manuals or keyboards of 44 keys each, a13note pedal keyboard, and an expression
(swell) pedal for controlling the volume. All tones are produced by electro-magnetic tone generators and
electrically amphfied. Selection of tone colors is made by adjusting 17drawbars and 6preset tabs. Other
characteristics of the music are adjusted by means of 10 other tabs. Atoggle switch, located to the right
\of the console above the manuals, is used to turn on the organ. Apilot Ught shows when the organ is
:turned on.
^Model L-lOOA is similar to Model L-lOO, with the addition of percussion voicing circuitry, controlled
from the lower left end block.
Model L—100— 1is similar to L—100, with asix-voice percussion feature added. Percussion controls are
mounted in the lower right end block.
Model L-100-2 is identical to Model L-100-1, with the addition of the ''drawer" type automatic
Rhythm II feature. No service information for Rhythm II is contained in tliis manual, since its circuitry
\is independent of the organ. For Rhythm II service information, refer to the Service Manual for Rhythm II
IHO~466.
Model L—200 with inbuilt rhythm is electrically identical to the L— 100—2organ. Wiring of the rhythm uni
to the console is presented in Figure 5—20.
L—Series organs will have fuses added to the Canadian power supply (101—000130) to comply with C.S.A.
standards. Location and value of fuses are shown in Figure 5—19.
For convenience in location desired information, this manual is divided into the following sections:
For convenience in locating desired information, this manual is divided into the following sections:
I. How the Organ Operates
II. Theory of Operation
III. Disassembly
IV. Practical Service Suggestions
V. Diagrams
VI. Parts List
SPECIFICATIONS
DIMENSIONS: Width, 43y2"; Height, 44^2"; Depth, 23"
WEIGHT: 215 lbs.
POWER INPUT: 140 Watts

SECTION I
HOW THE ORGAN OPERATES
1-1. GENERAL -This section contains a
description of the operating principles of
L—100 Series organs. Figures 1—1 and
1-2 depict the locations of the various
subassemblies. Figure 1-3 is ablock
diagram.
1-2. TONE SOURCE -Most tone sources, such
as strings, reeds, or pipes, produce complex
tones. The Hammond tone-producing
mechanism, however, generates individual
frequencies which can be combined by
means of harmonic drawbars to produce any
desired tone quality. The block diagram,
Figure 1-3, shows the chief components
of the instrument.
Electrical impulses of various frequencies
are produced in the "tone generator
assembly" whicli contains anumber of
"tone wheels" driven at predetermined
speeds by amotor and gear arrangement.
Each tone wheel is asteel disc similar to a
gear, with high and low spots, or teeth, on
its edge (see Figure 1-4). As the wheel
rotates, these teeth pass near apermanent
magnet, and the resulting variations in the
magnetic field induce avoltage in acoil
PEDAL
DRAWBAR CONTROL
TABS
LOWER MANUAL
DRAWBARS PILOT
LIGHT OFF-ON
SWITCH
UPPER OR
SOLO MANUAL
LOWER OR
GREAT MANUAL
PEDAL'KEYBOARD EXPRESSION
(VOLUME) PEdAL
Figure 1-1. L- 100 Console, Front View

SELF STARTING
SYKCHRONOUS MOTOR CONTROL
SWITCH ASSEM. PERCUSSION
CUT OFF ADJUST PEDAL CLICK
FILTER
wound on the magnet. This small voltage,
when suitably filtered, produces one note of
the musical scale, its pitch or frequency
depending on the number of teeth passing
the magnet each second.
Anote played on either manual of the
organ consists of afundamental pitch and
anumber of harmonics, or multiples of the
fundamental frequency. The fundamental
and harmonics available on each playing
key are controllable by means of drawbars.
By suitable adjustment of these controls
the player may vary the tone colors at
will. Several pre-selected tones are also
available by use of the preset tabs.
Mixed tones from the upper manual and
lower manual and pedals go through the
pre-amplifier and the "vibrato amplifier".
Vibrato may be added, depending on the
position of the vibrato selector tabs. The
tones then pass through the expression
control and additional stages of amplifica-
tion before reaching the speaker.
Percussion tones are produced by borrow-
ing asignal from the upper manual 2nd
harmonic drawbar, 3rd harmonic drawbar,
or both, and conducting the signal through
the percussion amplifier, where its decay
characteristics are controlled.
Aportion of this signal is returned to the
respective drawbar. The percussion signal
is then combined with the signal from the
manuals after the vibrato system but before
the expression control. The control tubes
are keyed through the 6th harmonic key
contacts and busbar.
The pedal tones do not require drawbars
for tone color variation, because they are
produced as complex tones by special
tone wheels. The single pedal drawbar
adjusts the volume of the pedals relative
to that of the manuals, and the pedal signal
then is combined with the signal from the
manuals before passing into the matching
transformer.

LEGEND NOTE:
L-100 SERIES ORGAN AMPLIFIER BLOCKS BEARING LIKE NUMBERS ARE ON SAME CHASSIS.
L-100A SERIES ORGAN 'FOLLOWING CONSOLES HAVE BRILLIANCE TABLET ADDED:
L-10.0-1 SERIES ORGAN "OOEL L-101 SERIAL #41622 AND ABOVE
MODEL L-102 SERIAL «42028 AND ABOVE
L-100-2 SERIES ORGAN MODEL L-103 SERIAL «43102 AND ABOVE
Block Diagram, IrlOQ Series

MAGNET- COIL OUTPUT TERMINAL
ONE SIDE OF COIL GROUNDED
-TONE WHEEL
COIL
Figure 1-4. Typical Tone Generator
-3.
-4.
MOTOR AND POWER SWITCH. -The tone
generator assembly, in which all tones of
the organ originate, is driven at constant
speed by aself starting synchronous motor,
operating at 1800 RPM, located at the left
side (rear view) of the console (Figure
1-2). (In 50 cycle organs, the generator
speed is 1500 RPM).
Atoggle switch (Figure 1
power to the organ.
-1) controls
TONE GENERATOR. -All tones of the organ
originate as electrical signals in the tone
generator assembly. It contains 87 tone
wheels having various numbers of teeth,
with suitable gears for driving them at
various speeds from amain shaft extending
along the center. Each pair of tone wheels
is mounted on ashaft and between them is
abakehte gear held by acoil spring, forming
amechanical vibration filter. As the gear is
not rigidly attached to the shaft, any pair
of wheels which may be stopped acciden-
tally will not interfere with the operation
of the others.
Adjacent to each tone wheel is amagnetized
rod with apickup coil wound on it. These
magnets extend through the front and back
of the generator, and are held by set screws
which can be loosened in case adjustment
is ever necessaiy. Figure 1-5 shows the
location of the magnet for any frequency
number. In the illustration the dotted lines
indicate frequencies whose tone wheels are
on the same shaft.
On top of the tone generator assembly are
small transformers and condensers, forming
tuned filters for the higher frequencies.
They are not likely to need replacing. In
case one filter becomes inoperative, both
the transformer and condenser must be
replaced with amatched set from the
factory. Figure 1—6 shows the location of ^
these filters. Afew frequencies use untuned
filters consisting of coils alone.
Wiring from the various filter assemblies
leads to the terminal strip on the long edge
of the generator.
The output frequencies of the tone genera-
tor are numbered, for convenience, in order
of increasing frequency. The lowest, number
§)@)@(8l)@(g)@)@@@@)@)©
\® \@ \0 \@ \e \® \<s \0 \@ \e \@ \@
s\ @)\ @\ @\ @\ 60 (56) g)\ e
SYNCHRONOUS
MOTOR CNO BACK OF GENEBATOR
(AT BACK OF CONSOLE)
SyNCHRONOUS
FRONT OF GENERATOR MOTOR END
DOTTED LINES SHOW FREQUENCIES WHOSE TONE WHEELS ARE ON SAME SHAFT
Figure 1—5. Magnet Locations on Tone Generator

L1,is about 32 cycles per second, and the
^highest, number 91,is about 6000 cycles
per second. Frequency numbers 1to 13are
used only for the pedals; numbers 14 to 17
are omitted; and numbers 18 to 91 are used
for the manuals. Figure 1-6 showing filter
locations also shows the termination point
i
»of each frequency, while Figure 5-1 shows
typical tuned and untuned tone generators.
I
^In case any generator frequency is weak or
[absent, refer to ''Practical Service Sugges-
tions" for the procedure to be used in
locating and correcting the trouble.
1-5. MANUALS. -Musical frequencies from the
tone generator go through the manual cable
to terminal strips on the two manuals and
from them to the key contact springs.
Each of the two manuals has 44 playing
keys, or approximately SVi octaves. The two
manuals do not cover exactly the same
pitch range, but they are arranged so that
keys of like pitch are in line. Middle "C" is
the first Con the upper manual and the key
in line with it on the lower manual.
Under each key are anumber of contact
springs (for the fundamental and harmonics
of that key) which contact an equal number
of busbars when the key is pressed. All
contact springs and busbars have precious
metal contact surfaces to avoid corrosion,
and the manuals are sealed to exclude dust
so far as possible. In case acontact becomes
dirty in spite of these precautions, abusbar
shifter is provided in each manual to slide
the busbars endwise and thus provide a
fresh contact surface. (See paragraph 4-3b).
Looking under the lower manual on the
left hand end (front view) ablack wood
end block will be observed. One half inch
from the front of this block is adrilled hole.
Within this drilling is asmall metal tongue
with apunched hole. Using either long nose
phers or ahook, this tongue can be moved
in and out and it in turn moves the busbars.
The upper manual shifter is in asimilar
place and access to it is from the rear of the
console.
The key contacts are connected through
resistance wires to the manual terminal
strips. The manual wiring chart. Figure 1-7,
shows how the contacts of each key are
connected to the proper frequencies to
supply the fundamental and harmonics of
that particular key. The blank spaces
indicate that no key contact is used, inas-
much as the higher harmonics of these
keys are not required. Since the percussion
control circuit is keyed through the 6th
harmonic busbar, the blank spaces in this
row have contacts connected to ground
through resistance wires.
The busbars of each manual, each one
carrying acertain harmonic, are wired to
the appropriate harmonic drawbars for
that manual through the "Drawbars" tab.
NUW&ERS ON FILTER TRANSFORMER*. ARE FRE.QUENCY NU^ABERS
OF TRANSFORMERS
SYNCHRONOUS
MOTOR END
FILTER TRANSFORMERS
42 78 18 S4 ^5 71 II 47 28 61 488 81 21 57 36 74 50 43 79 19 S5 36 72 ,2 48 29 65 569 82 22 58 i3_75 5l_32^ 68 844_25_6I__^
8S 30 £6 690 83 23 59 40 7«, 52 3i 69
o.oolE Qo6nTro o'o'o'o'o'o'o" o~cro~o"oo" <-3 oQ"ol!o oo' obooboo o6o6"o ooooooood||o oo"o^ oooobo.
945 26 62 28fe 3» 67 791 84 24 60 41 77 53 34 70 10 46 27 63387 80 20 56
OUTPUT TERMINAL FREQUENCY NUMBERS"
boboooooeo o-o-c
.37 73 13 49 ^
Figure 1-6. Filter Locations and Frequency Terminations on Generator Cover
1-5

ER MANUAL
H/
SL
RMCN CBUSBAR
ILAD COLOR FRFQUENCY NUMBERS
B-FUND BROWN 18 20 2122 23 24 25 26 27 28 29 30 31 32 33 3435 35 37 38 39 40 42 43 44 45 46 47 48 49 50 51 52 53 54 58 bI
FUND ORANGE 30 31 32 33 34 3536 37 38 39 40 4243 4445 46 47 48 49 50 5152 53 3+55 56 57 58 59 60 6162 63 64 65 6667 && 69 /O 7172 73
3RD GREEN 49 50 51 52 53 54 55 56 57 58 59 60 6162 63 64 65 66 67 69 70 7172 73 74 75 76 77 78 79 808182 8384 85 86 8768 8990
4TH BLUE 54 55 56 57 58 59 60 6162 63 64 65 66 6758 59 70 7172 73 74 75 76 7 7 78 79 80 8182 83 848566 8788 8990 91
STH VIOLET 58 59 60 6162 63 64 65 66 67 68 69 70 7172 73 74 75 76 7 7 7 879 80 8182 83 84 85 86 87 88 B9 90 91
8TH WHITE 66 67 68 69 70 7172 73 74 75 76 78 79 80 8182 83 84 85 86 8788 89 90 91
2ND YELLOW 42 43 44 4546 47 4849 50 5152 53 54 55 56 57 58 59 60 6162 63 64 65 66 67 68 69 70 7172 73 74 75 76 77 78 79 80 6182 83 84 85
SUB-3 RD RED 37 38 39 40 41 42 43 44 45 46 47 48 49 50 5152 53 54 55' 56 57 58 59 60 6162 63 64 65 66 67 68 69 70 7172 73 74 75 76 77 78 79 80
6TH GREY 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 62 83 84 85 86 87 88 69 9091 **'* ;* **•* ****
NOTES
FF* 6AA* BC|C*^ DD* EFf'^ gg^ aa^I bcdeUIk* G|g* aA*| BIC|C*| D|d*| E I
F|f*| G|g*| A|a*| B
IC\c^\ D|d'| E|F|f^| 6|g^| A|a-^| B|C
61
71819I'oj" 1
I2jl3|l4|l5|l6|l7|l8| I9|20 2l[2 2|23[24|25j26|2 7|28|29|3o|3l|32|3 3j3 4|35|36|37|38 39|40|4l|42|43|4 4j45j4 6|47|4&j49|50j5l|52|53|54|55|56 57|58j59|60|6l
KEY NUMBERS
FREQUENCY NUMBERS BUSBAR
LEAD COLOR HARmO NIC
LOWER MAh
i8 19 20 2122 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 5152 53 54 5 5 56 57 58 59 60 61BROWN FUND
30 31 32 33 34 35 3fe 37 38 39 40 4243 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 7172 73 RED 2ND
46 47 46 49 30 51 52 53 54 55 56 57 58 59 60 6162 63 64 55 66 6768 69 70 7172 73 74 75 76 77 78 79 80 8182 83 84 85 86 87 88 89 GREEN 5TH
49 50 5152 53 54 55 56 57 58 59 60 6162 63 64 55 66 676S 6970 7172 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 69 90 91BLUE 6TH
54 55 56 5756 59 60 6162 63 64 65 66 6768 69 70 7172 73 7576 7776 79 80 8182 83 84 85 8687 88 89 90 91VIOLET 8TH
37 38 39 40 42 43 44 45 46 47 48 49 SO 51 52 53 54 55 56 57 58 59 60 6162 63 64 65 66 67 68 69 70 7172 73 74 75 76 77 78 79 80 ORANGE 3RD
42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 6162 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 YELLOW 4TH
*CONTACTS GROUNDED THROUGH 16 OHMS
Figure 1-7. Manual Wiring Chart

1-6. HARMONIC DRAWBARS. -The left group
of seven harmonic drawbars (Figure 1—8)
is associated with the lower manual, and
the right group of nine drawbars controls
the upper manual. By sliding these drawbars
in and out, the organist is able to mix the
fundamental and harmonics (or overtones)
in various proportions. The distance abar
is pulled out determines the strength of the
corresponding harmonic; and if adrawbar
is set all the way in, the harmonic it repre-
sents is not present in the mixture. Neither
manual will play unless one of its drawbars
.is pulled out at least part of the way with
the drawbar tab pressed, or apreset tab is
pressed.
The drawbars sUde over 17busbars, repre-
senting intensity levels. As the drawbar
moves, its contact is touching some busbar
at all times, and therefore there is asmooth
change in volume of that harmonic.
These busbars extend the length of the draw-
bar assembly, and are connected to the
low impedance primary of amatching
transformer. Signals from the high imped-
ance secondary of this transformer go to
the preamplifier input. The matching
transformer is located within the preampli-
fier chassis.
1-7- PEDAL DRAWBAR. -The center drawbar
adjusts the volume of the pedals. Its opera-
tion is similar to that of amanual drawbar.
1-8. PEDAL KEYBOARD. -The 13 playing pedals
are operated by the left foot and are con-
nected to the lowest 13frequencies of the
generator. Like the manuals, they have
light and dark keys arranged in the standard
octave pattern. Figure 1—9 identifies the
pedals and shows the generator frequency
number associated with each. Asingle
contact on each pedal closes when the pedal
is pressed, thereby allowing the correct
generator frequency to reach the amplifier.
1-9. EXPRESSION PEDAL. -The expression
pedal, sometimes called "swell" pedal
(Figure 1-1) is operated by the player's
right foot and varies the volume of both
manuals and pedals together. When the
pedal is tilted back (closed) by pushing on
the player's heel the music is softest, and
when pushed forward (opened) by the
player's toe the music is loudest.
Figure 1-8. Drawbars &Control Tabs (Partial View)

PEDAL CONTACTS
Jlllll lllllll I
Figure 1—9. Pedal Keyboard
1-10. CONTROL TABS. -There are 17 tabs on the
L-lOO series instrument, each providing
some change in the instrument's operation.
To have the instrument sound after turn-
ing it on, tabs such as FULL ORGAN and
ENSEMBLE will place the upper and lower
manual in operation. Atab is in use when
in the down position. Functions of the
various tabs from left to right as they
appear on the instrument are given in the
following paragraphs.
1-11. PRESET TABS. -Four tabs are provided
for the upper manual and two for the
lower manual. As indicated, they provide a
choice of using the drawbars or playing the
preset tones indicated on them.
1-12. VIBRATO TABS. -The L-lOO series organs
are equipped with 3tabs which vary the
vibrato effect. Three degrees of vibrato
are available using the VIBRATO NORMAL,
VIBRATO SMALL or both together.
VIBRATO CHORUS can be used with
VIBRATO NORMAL, VIBRATO SMALL,
or both, to provide different degrees of
chorus.
1-13. REVERBERATION AND VOLUME SOFT
TABS. -Several degrees of reverberation
are obtained by the use of either or both
tabs labeled REVERB Iand REVERB 11.
These tabs, in addition to turning this feature
on, govern the loudness or amount ofrever-
beration by aresistive network used in con-
juntion with the speaker. The VOLUME
SOFT tab controls the overall volume of the
organ and is especially useful where playing
1-14. PERCUSSION CONTROL TABS -There are
four of these tabs which operate only when
the upper manual DRAWBARS tab is de-
pressed. Pressing either the SECOND
HARMONIC or THIRD HARMONIC tab
will, when the upper manUal is played,
cause the tone to sound percussively (in
addition to sustained organ tones). Both
tabs can be depressed, giving acombination
percussive tone. The FAST DECAY tab
causes the percussive tones to fade away
with greater rapidity. PERCUSSION SOFT
reduces the volume for the percussive signal.
Operation of the electrical circuits associated
with this feature is described in subsequent
paragraphs.
1-8

1-15. L-100A PRESET PERCUSSION UNIT (See
Figure 1-10).- When added to the L-lOO
series instrument, this unit adds five pre-
voice percussion effects, including reiter-
ation in three speeds. It also provides three
percussion effects, "Normal (Non-Vibrato)",
"Vibrato", and "Delayed Vibrato". For the
rhythm accompaniment it also provides a
"Cymbal-Brush" effect, the "Brush" being
on the lower manual, and available when
played in alegato fashion each time akey is
depressed. The "Cymbal" is available on the
pedal and sounds each time apedal is de-
pressed. The "Cymbal-Brush" control turns
these effects on and selects the "Cymbal-
Brush" volume.
1-16. SELECTOR SWITCH. -With the Selector
Switch in the "Drawbar" position, the
signals from the upper manual harmonic
busbars are routed to their associated
drawbars in the upper manual group. The
following is abreakdown of the harmonic
switching used.
1-17. HARMONIC BUSBAR SWITCHING AND
REITERATION SPLIT. -Upper Manual.
The Sub-Fundamental, sub-third and eighth
harmonics are not switched. The sixth har-
monic busbar is used for percussion keying.
With the Selector Switch in the "Drawbar"
position, all harmonic busbars are routed to
.their associated drawbars.
1-18. L-100-1 SIX-VOICE PERCUSSION FEATURE
(See Figure 1-11). -
1-19. LOCATION OF CONTROLS. -The rhythm
controls are located on the right end block
of the lower manual.
1-20. VOICING. -The following voices are
available. BLOCK
CYMBAL
BRUSH
BONGO
TOM-TOM
CLAVES
1-21. OPERATION OF CONTROLS. -Any of the
six voices may be played at any time by
means of the momentary push buttons
associated with the rocker tabs.
The BLOCK and CYMBAL voices are pro-
grammed into the pedal keyboard when
their rocker tabs are "on". The remaining
four voices are programmed into the lower
manual keys when their rocker tabs are
on .
Chime
REITERATION SPLIT
"A" CHANNEL "B" CHANNEL
2nd
3rd
4th
(5th to Freq. Div.)
(1-1/4 From Freq. Div.)
DRAWBARS
Fundamental
Guitar Fundamental
3rd
4th
5th
2nd
Marimba Fundamental 2nd 3rd
4th
5th ,
Xylophone Fundamental 3rd 2nd
4th
5th
Banjo 2nd
3rd
4th
5th
Fundamental
1-9

Figure 1-10. HOOA Preset Percussion Unit
1-10

1-22.
1-23.
The RHYTHM VOLUME control, mounted 1-24.
to the right of the rocker tabs, regulates
the loudness of the rhythm voices relative
to the other organ voices. The organ's
expression pedal also affects the rhythm
voices except brush and cymbal.
The BRUSH and CYMBAL voices sound
without reverberation. The remaining voices
are reverberated whenever aREVERB tab
on the organ's control panel is depressed.
EXTERNAL EQUIPMENT. -The L-lOO
Series organs may be equipped with ex-
tension speakers, external inputs and
earphones.
EXTENSION SPEAKERS. -AHammond
Model PR-40 Tone Cabinet may be used
as an extension speaker. ATone Cabinet 1-25.
Control Kit, P/N AO-22625-2 is required
for proper interconnections. Installation
instructions are furnished with the kit.
EXTERNAL SOUND SOURCE. -Arecord
player or microphone equipped with a
suitable preamplifier, or aradio, can be
played through the organ's speakers. The
device used should have an output level of
about 1/2 volt rms maximum, and should
have its own volume control, since the
organ volume controls will not affect the
signal. The organ may be played at the
same time.
To connect an external sound source, a
Switchcraft Type 330 Fl "Y" connector is
required. Remove the connector cable from
the WH terminal on the power amplifier.
Insert the ''Y" connector into the terminal,
and insert cable previously removed into
one arm of the "Y". Connect external
sound source to the other arm.
EARPHONES. -hi order to use earphones,
the output jack and network shown in
Figure 1-12 are required. When earphones
are in use, organ speakers are silenced.
GN.
BLK.
Organ
Spk.
wires 47a
SWITCHCRAFT
SF-JAX #25 OR 55
ji
Use Koss
Model
SP-3.
Figure 1—12. Earphone Adapter Circuit

SECTION II
THEORY OF OPERATION
2-1. GENERAL. -This section contains circuit
descriptions of the ampUfier chassis, and
the percussion attachments. There are
three amphfier assembhes in the L—100
series instruments. On the upper shelf as
viewed from the rear, to the left is the
vibrato amphfier, towards the center the
preamplifier and percussion amphfier,
while the reverberation and power amplifier
is located on the lower shelf.
2-2. PREAMPLIFIERS (See Figure 5-1). -The pre-
amplifier (VI) receives all signals impressed
on the matching transformer secondary,
which originate by use of the drawbars or
preset tabs. Should any percussion tab be
in use, a portion of the second, third or
both harmonics of the upper manual wiU
also appear in the input circuit of the per-
cussion amplifier which will be discussed
further on.
2-3. VIBRATO PHASE SHIFT AMPLIFIER (See
Figures 5-1 through 5-4). -The vibrator
system varies the frequency of the tones
by continuously shifting their phase.
Circuit components include three series-
connected vacuum tube phase shifter stages
(V2A, V2B, and V3A), associated saturable
reactors (SRIOI, SR102, SR103), voltage
amphfier (V3A), vibrato oscillator (V4A),
and driver stages (V4B, V5).
Asingle low frequency oscillator (V4)
provides the rate for the vibrato system
(approx. 6.8 CPS). With either the normal
or small vibrato tab in use, this oscillator
impresses its signal on V4, acathode fol-
lower and isolation stage. Positive pulses
now appear on the grid of driver tube V5.
The plate circuit of this tube is in series
with three saturable reactors located in the
plate and cathode circuits of the phase shift
stages. Irrespective of which vibrato stop is
used, the rate remains constant, but the
degree of vibrato is determined by the
amplitude of the positive pulse on the
driver tube.
The continuous phase shift is accomplished
by using 180° out-of-phase signals from the
plate and cathode of each shifter stage and
controUing them with the saturable reactors.
Plate and cathode resistors are of equal
value and consequently signals are equal in
amplitude in each plate and cathode circuit.
The saturable reactors serve as ameans of
providing avarying composite of signals
from both plate and cathode of each stage,
ranging from virtually full cathode signal to
full plate signal.
The driver tube plate current varies from
about .5ma to 5ma. at vibrato rate. This
current varies the degree of saturation in
the reactor cores and results in asmoothly
varying impedance.
At minimum driver current (when the
voltage feeding driver tube V5 is negative
and driver tube is nearly cut off) the
reactor impedances are maximum and are
large compared to the 15000 ohm plate,
circuit series resistors Rl 04, Rl 10, Rl 15.
Therefore, under this condition most signal
will emanate from the plate. (The reactors
being virtually short circuited by the plate
circuit series resistors) and phase shift will
be maximum -approaching 180° -since
plate voltage is 180** out of phase with grid
voltage.
At maximum driver current (when voltage
feeding driver tube V5 is positive and driver
tube is conducting maximum current) the
reactors are saturated and their impedance
is aminimum —small compared to the 15OO0
ohm plate circuit series resistors R104,
Rl 10,R1 15. Therefore, most signal will
emanate from the cathode (the saturated
and low impedance reactors virtually short
circuit the plate circuit series resistors) and
phase shift will be aminimum -approach-
ing 0° —since cathode voltage is in phase
with input grid voltage.
Between these extremes, the phase varies
smoothly under control of the saturable
reactors. ^
The continuous change in phase is equi-

valent to acontinuous frequency vari-
ation, and thus the frequency varies up and
down at vibrato rate.
PERCUSSION AMPLIFIER (See Figures 5-1
through 5-4). -The 2nd or 3rd harmonic
signal, or both, when these tabs are de-
pressed, will be impressed upon the input
of the 2N306 transistor. The output of
this transistor is resistance coupled to the
one half of VI 1which acts as acontrol
tube and is normally conducting, so when a
tkey is depressed the percussive note first
sounds loudly. It passes through the control
tube and aband pass filter and is impressed
on the grid terminal of VI.
Immediately the note begins to fade away,
giving the characteristic percussion effect.
This fading is accomplished as follows: When
jf either harmonic stop is depressed the key-
iing wire (normally held at plus 28 volts
through anti-spark resistor R21 5) is con-
nected to solo manual 6th harmonic draw-
bar. When akey is pressed this keying hne
^is grounded through the key contact and
tone generator filter. This virtually grounds
the grid and plate of VI 1(connected as a
diode) open-circuiting the tube and isolating
[the control tube grid circuit. The grid of
the control tube drifts from its operating
potential of about 25 volts to acutoff potential
potential (about plus 15volts) at arate
determined by the time required for C210
3to discharge through R219 and R409.
The percussion signal is now blocked. No
percussion notes can sound until all keys of 2-5.
the solo manual are released and the control
grid again rises to plus 25 volts. The time of
this rise (that is, how quickly the control
tubes turn on again after the key is released)
is the time required to charge C2 10to plus
25 volts through R218.
When a''percussion" tab is pressed the solo
manual second, third, or both harmonic
*manual busbars are connected to the green
percussion signal line and a5OHM series
resistor is connected between the manual
bus wire and drawbars providing for asus-
tained signal in addition to the percussion
signal. The 6th harmonic drawbar is dis-
connected from its lead wire and this wire
(which is grounded through the generator
magnets when any key is pressed) is used
to turn off the control tube. Therefore the
6th harmonic is not available on the upper
manual when the percussion is in use.
When the PERCUSSION SOFT tab is down,
it reduces the volume by shunting resistor
R224 into the dividing network composed
of R222 and R223.
The PERCUSSION FAST DECAY tab
determines how fast the sound fades away
after akey is pressed. When the tab is up,
resistor R21 9discharges capacitor C21 0, re-
ducing the D.C. voltage on the control tube
grids to cut-off in about 2-1 /2 seconds.
When the tab is down, resistor R409 is
shunted across resistor R21 9, reducing the
time to discharge capacitor C210 and there-
by reducing the D.C. voltage on the control
tube grid to cut off in less than one-half
second.
With either or both 2ND and 3RD HAR-
MONIC tabs down, the harmonic drawbar
wires are connected to the -green signal input
wire of the percussion amplifier. Either or
both signals are fed back to their respective
drawbars by resistors R410 and R41 1which
are shorted out when the percussion tabs
are not in use.
The percussion signals as well as the signals
from the vibrato and phase shift amphfier
are combined in the input circuit of cathode
follower VI and are sent to the expression
control, which is also connected to the
input of the reverberation and power
amplifier.
REVERBERATION AND POWER AMPLIFIER
(See Figure 5-4). -The combined signals
from both prior mentioned amplifiers (after
the expression control has acted upon them)
are impressed on the grid of V6 and in turn
on V7, the reverberation drive tube. After
passing through the reverberation unit the
signal is again ampUfied by V6 and passed
through aresistive network, components of
which are variable, permitting the reverbera-
tion to be available in several intensities
and "off. From the input of V7 (the
reverberation drive tube) asignal is shunted
around the reverberation unit and its control
features which provide apath for the non-
reverberation signal. The input of V8 re-
ceives this signal as well as areverberative
signal. This common input line also contains
the VOLUME SOFT tab circuitry.
The output of the second half of V8 is a

phase inverter driving push-pull output
tubes V9 and VI 0. Afeedback circuit from
the output transformer secondary (R336
and R337) makes the pedal response more
uniform by reducing speaker resonance.
IR336 is adjusted at the factory.
2-^6. POWER SUPPLY (See Figure 5-4). -The
power supply uses a 5U4 rectifier tube
with conventional filtering circuit.
2-7. L-10QA PERCUSSION VOICING CIRCUITRY
(See Figure 5-5).
2-8. MODE SWITCH -With the ''Mode Switch"
in any of the reiteration positions, the
harmonics necessary to produce the
"Chime", "Guitar", and "Banjo" are all
fed into the "A" reiteration channel only,
while the "Marimba" and "Xylophone"
effects feed harmonics into both the "A"
and the "B" channels. This spht into the
"A" and "B" channels only occurs with the
use of reiteration. Without reiteration, all
effects are routed into the regular percussion
system. The two reiteration channels are
identical. You will note that across the
secondary windings of the two input trans-
formers is located afield-effect transistor.
These gates Q300 and Q303, are fed alter-
nating pulses from abistable multivibrator
which supplies alternate pulses to each one
of these gates. That is; one is On, while the
other is off. These gates shunt the signal
to ground, thereby making the channel
inoperative. These individual signals are
further amplified by aone stage transistor
amplifier, Q301 for the "A" channel, and
Q302 for the "B" channel. They are then
mixed together and fed to acommon
amphfier, Q307, which in turn feeds this
percussion signal to the input side of the
swell pedal. The multivibrator which
supphes the keying pulse for these two
gates does not run continually, but rather
is turned off and on each time akey is
depressed on the upper manual. The multi-
vibrator consists of Q305 and Q306. The
multivibrator rate varies with the applied
base voltage. This voltage is applied through
the "Mode Switch" and R684 and R685.
Q304 provides the necessary switch pulse
to start the multivibrator.
NOTE
Whenever the reiteration is used,
it completely bypasses the percus-
sion section of the AO—42 amplifier.
With the "Mode Switch" in the "Normal",
"Vibrato", or "Delayed Vibrato" position,
the various pre-voiced percussions are
routed to apercussion preamphfier made
up of Q314 and Q313. These amplified
signals are then routed into the regular
Hammond percussion system at the col-
lector of Q201. With the "Mode Switch"
in the "Normal" position all percussion
voices sound as normal; that is, they have
no vibrato.
NOTE
To obtain the following vibrato
effects it will be necessary to de-
press one or both of the VIBRATO
tabs.
With the "Mode Switch" in the "Vibrato"
position, aportion of the percussion signal
is taken from the input side of the Expres-
sion pedal and routed through R670, the
"Mode Switch", and is then fed to the grid
of VI A(Pin 2). Here the percussion voices
are amplified and fed to the vibrato phase
shift ampUfier. All voices so routed now
appear with vibrato.
With the "Mode Switch" in the "Delayed
Vibrato" position, aportion of the percus-
sion signal is taken from the input side of
the Expression pedal, and routed to a
voltage divider made up of R682 and R681.
This weak signal is fed to the base of Q3 12.
It will be noted that the emitter of this
stage is not bypassed and that the output
of this stage is relatively low. During keying,
after apredetermined time lag (.5 seconds),
the charge on C631 is depleted by Q308
and Q309. With this charge depleted, Q308
and Q309 stop conducting and their
respective collectors assume the supply
potential +12V. This +12V. from the
collector of Q309 is now apphed to the
base Q3 10, thereby placing Q3 10and Q3 1
1
in astate of conduction. With Q3 11now
conducting, C633 is placed across the
emitter resistor of Q3 12. This materially
increases the gain of this stage, and as the
percussion is dying away, feeds this ampli-
fied portion of the fading percussion signal
through the "Mode Switch", and R683 to
the grid of VI A(Pin 2). There the signal
is ampUfied and fed to the Vibrato Phase-
Shift amphfier. All voices so routed now
appear with avibrato tail-off.

Two positions of the ''Mode Switch",
"Vibrato", and "Delayed Vibrato" also
effect the normal Hammond percussions
Iwhen they are in use (See Note above).
2-9. FREQUENCY DIVIDER -When using the
"Chime" voice, it is necessary to create a
\1-1/4 harmonic for the proper reproduction
of the "Chime" tone. This is accompHshed
by routing the 5th harmonic into an ampli-
fier made up of Q315 and Q316. Q317
'rectifies and further amplifies this pulse
which is then fed to atwo-stage frequency
divider, made up of Q318, Q319, Q320,
\and Q321. The output of this second
Ifrequency divider is then routed back to
Ithe "Selector Switch", and is used as one
of the harmonics in the "Chime" voice.
NOTE
jBecause afrequency divider can cv
Ihandle only one frequency at a
time, any attempt to play two or
more "Qiime" notes at atime will
result in distortion.
^2-10. CYMBAL AND BRUSH -The "Cymbal-
Brush" switch when in the "off" position
disables the keying functions necessary to
produce the "Brush" effect. With the
"Cymbal-Brush" switch in any one of the
"on" positions, the 8th harmonic of the
lower manual is disabled and this harmonic
busbar is used for keying the "Brush" effect.
The pedal signal (keying) contact is used to
activate the "Cymbal" effect each time a
pedal is depressed.
,2-11. BRUSH KEYING -With the "Cymbal-Brush"
'switch in any of the ON positions, the base
of Q322 is routed now to the 8th harmonic
busbar in the lower manual. Anytime akey
is depressed, the base voltage of this tran-
sistor is routed to ground, and this stage
'stops conducting. The attendant rise in
collector voltage is impressed on one plate
of C608. The other plate of C608 responds
by driving excess electrons off to ground
through resistor R624. The resultant posi-
tive voltage is then fed through D203 to the
base of Q323, the "Brush" gate. To the base
of this "Brush" gate is also fed the noise
from the noise generator Q324. This noise
is now tuned in the collector circuit and
fed to the "Cymbal and Brush" ampUfier
iwhich comists of Q325 and Q326.
2-12- CYMBAL KEYING. -Anytime apedal is
depressed, the pedal signal is routed to the
pedal drawbar. Aportion of this same signal
is also fed to Q327 and Q328. These stages
amplify and shape the signal and feed it
through R61 2to the base of Q330, and
through R613 and D205 to aR/C storage
network and the base of Q329. The signal
developed across R616, the emitter resistor
of Q330, is rectified by D204 and this posi-
tive voltage is applied to the base of Q331,
the "Cymbal" gate, turning it on. At the
same time, the output of Q328 is being
rectified by D205 and slowly appUed to the
base of Q329. When Q329 is biased into
conduction it depletes the base bias nor-
mally supplied to Q330 through R612 and
Q330 stops conducting. In this state, no
signal is available at the emitter of Q330
to be rectified, and Q331, the "Cymbal"
gate, slowly turns off. To the base of this
"Cymbal" gate is also fed the noise from
the noise generator, Q324. This noise is
tuned in the collector circuit of Q33 1and
fed to Q325 and Q326 the "Cymbal and
Brush" amplifier.
2-13. BRUSH AND CYMBAL AMPLIFICATION. -
After being ampUfied by Q325 and Q326, the
"Brush and Cymbal" signals are routed to a
voltage divider consisting of R604, R605, and
R606. It is then tapped by the switch and
routed to R602 the overall level control.
This is located on aterminal strip on the
lower organ shelf, near the AO—43 ampli-
fier. The wiper of the overall level control
(R602) now feeds into the AO—43 ampli-
fier through R601 and C318 to Pin 7of
V8. To enhance the "Brush and Cymbal"
effects, asmall high frequency speaker is
attached to the main ampHfier. It is located
under the lower right hand end block on
the organ.
2-14. POWER SUPPLY. -Power supply chassis is
suppHed with +340 volts DC from AO-43
amplifier. +80 volts required for percussion
assembly is obtained from voltage divider
R690, and R69 1.+12volts is obtained
from Zener Diode D201.
2-15. L-100-1 SIX-VOICE PERCUSSION CIR-
CUITRY. -
2-16. POWER SUPPLY (See Figure 5-7). -
Power supply components are located in
the power supply chassis assembly (127-7