Hammond Organ L-100 Series User manual

INTRODUCTION TO REVISED MANUAL
Welcome to the revised edition of the Hammond L–100 Series
Service Manual.
Started in late 2018, this edition updates the original manual for
the modern era. Changes include:
• Schematics recreated in Illustrator allowing support for
interactive comparisons between models and a 17MB
reduction in le size
• Spelling and typographic mistakes corrected
• Hyper-links added to cross-references, table of contents,
gures, etc.
• Images touched up
• Most images added in-line with column text to aid on-screen
viewing
• Page layout redesigned for a compromise between
landscape printing and on-screen reading
• Font changed to sans serif (Helvetica Neue) for easier on-
screen readability
I–1 METHOD
The original service manual had been scanned by an unknown
source. This was then downloaded and OCR-ed.
OCR errors were either corrected or re-keyed. Then all text was
composited in Adobe InDesign. Images were captured, edited,
and enhanced in Adobe Photoshop.
I–2 REVISION HISTORY
The following revisions have been made:
Revision Date Comments
Original ca. 1961 Original service manual written by
Hammond Organ Company
1.0 November, 2018 Initial update by Michael
Hightower
1.1 February, 2022 Added Kon Zissis’ modications,
minor edits
To suggest corrections/improvements or to add content, please
contact Michael Hightower via [e-mail].
I–3 PRINTING INSTRUCTIONS
The main body of the document is typeset on 8.5” x 11” (US
Letter) in a landscape format. The schematics are typeset on 8.5”
x 14” (US Legal) in a landscape format.
Pages numbers and layout:
• 8.5” x 11 (US Letter) Landscape:
Cover page – 37
55 — End of document
• 8.5” x 14 (US Legal) Landscape:
39 — 54

Page iii
Table of Contents
1. How the Organ Operates ...........................7
1-1. General....................................7
1-2. Tone Source ................................7
1-3. Motor and Power Switch ......................8
1-4. Tone Generator..............................8
1-5. Manuals ..................................11
1-6. Harmonic Drawbars .........................13
1-7. Pedal Drawbar .............................13
1-8. Pedal Keyboard ............................13
1-9. Expression Pedal ...........................14
1-10. Control Tabs ...............................14
1-11. Preset Tabs ...............................14
1-12. Vibrato Tabs ...............................14
1-13. Reverberation And Volume Soft Tabs ...........14
1-14. Percussion Control Tabs .....................14
1-15. L–100A Preset Percussion Unit ................14
1-16. L–100–1 Six-Voice Percussion Feature...........15
1-17. External Equipment .........................16
1-18. Extension Speakers .........................16
1-19. External Sound Source ......................16
1-20. Earphones ................................16
2. Theory of Operation ..............................17
2-1. General...................................17
2-2. Pre-Ampliers..............................17
2-3. Vibrato Phase Shift Amplier ..................17
2-4. Percussion Amplier. . . . . . . . . . . . . . . . . . . . . . . . . 18
2-5. Reverberation and Power Amplier .............19
2-6. Power Supply ..............................19
2-7. L–100A Percussion Voicing Circuitry ............19
2-8. L–100–1 Six-Voice Percussion Circuitry ..........21
3. Disassembly ....................................24
3-1. General...................................24
3-2. Access ...................................24
3-3. Upper Manual Key ..........................24
3-4. Lower Manual Key ..........................24
3-5. Drawbar Contact Spring. . . . . . . . . . . . . . . . . . . . . . 24
3-6. Drawbar, Drawbar Knobs or Drawbar Assembly ...25
3 -7. Upper Manual..............................25
3-8. Lower Manual..............................26
3-9. Generator .................................26
3-10. Motor ....................................26
3-11. Pedal Keyboard ............................26
3-12. Swell Assembly ............................27
3-13. To Replace a Broken Tab .....................27
3-14. Pilot Light or Power Switch ...................27
3-15. Percussion Circuitry, L–100A ..................28
3-16. Six-Voice Percussion Circuitry, L–100–1..........28
4. Practical Service Suggestions......................29
4-1. General...................................29
4-2. Organ Performance Check ...................29
4-3. Equipment Required.........................29
4-4. Procedure ................................29
4-5. Vibrato ...................................30
4-6. L–100A Percussion Performance Check .........32
4 -7. L–100–1 Six-Voice Percussion Performance Check
And Troubleshooting ..............................34
5. Diagrams ......................................37
5-1. General...................................37
5-2. Interactive Schematic Instructions ..............37
6. L-Series Parts List ...............................55
6-1. Overview .................................55
6-2. Changes from Source Document...............55
6-3. Assembly List ..............................56
6-4. Parts List .................................58
7. Modifications ...................................81
7-1. Overview .................................81
7-2. Connecting a Leslie or Other External Speaker ....81

Page iv
7-3. Other Resources ...........................82
7-4. Revised RH End-Panel Layout Template .........82
7-5. Kon Zissis Chorus Depth Control...............86
7-6. Kon Zissis Percussion Mod ...................86
7-7. Kon Zissis Treble Boost Mod ..................87

Page v
INTRODUCTION TO ORIGINAL SERVICE MANUAL
II–1 OVERVIEW
This manual contains service information for L–100 Series organs.
The series is comprised of the following models:
L–100
L–100A
L–100–1
L–100–2
L–200
The Model L–100 Hammond organ is a completely self-contained
console, requiring no external tone cabinet. It has two manuals
or keyboards of 44 keys each, a 13 note pedal keyboard, and an
expression (swell) pedal for controlling the volume. All tones are
produced by electro-magnetic tone generators and electrically
amplied. Selection of tone colors is made by adjusting 17
drawbars and 6 preset tabs. Other characteristics of the music are
adjusted by means of 10 other tabs. A toggle switch, located to
the right of the console above the manuals, is used to turn on the
organ. A pilot light shows when the organ is turned on.
Model L–100A is similar to Model L–100, with the addition of
percussion voicing circuitry, controlled from the lower left end
block.
Model L–100–1 is similar to L–100, with a six-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 this manual, since its
circuitry is independent of the organ. For Rhythm II service
information, refer to the Service Manual for Rhythm II HO–466.
Model L–200 with inbuilt rhythm is electrically identical to the
L–100–2 organ. Wiring of the rhythm unit to the console is
presented in Figure 5–9.
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 5–17.
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
I V. Practical Service Suggestions
V. Diagrams
VI. Parts List
II–2 SPECIFICATIONS
DIMENSIONS: Width, 43½”; Height, 44½”; Depth, 23”
WEIGHT: 215 lbs.
POWER INPUT: 140 Watts
OUTPUT: 15 Watts, E.I.A.

Page 7
SECTION I
HOW THE ORGAN OPERATES
1–1 GENERAL
This section contains a description of the operating principles
of L–100 Series organs. Figure 1–1 and Figure 1–2 depict the
locations of the various subassemblies. Figure 1–4 is a block
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 1–4, shows the chief
components of the instrument.
Electrical impulses of various frequencies are produced in the
“tone generator assembly” which contains a number of “tone
wheels” driven at predetermined speeds by a motor and gear
arrangement. Each tone wheel is a steel disc similar to a gear, with
high and low spots, or teeth, on its edge (see Figure 1–5). As the
wheel rotates, these teeth pass near a permanent magnet, and the
resulting variations in the magnetic eld induce a voltage in a coil
wound on the magnet. This small voltage, when suitably ltered,
produces one note of the musical scale, its pitch or frequency
depending on the number of teeth passing the magnet each
second.
A note played on either manual of the organ consists of a
fundamental pitch and a number 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.
Figure 1–1: L–100 Console, Front View

Page 8
Figure 1–2: L–100 Console, Rear View
Mixed tones from the upper manual and lower manual and pedals
go through the pre-amplier and the “vibrato amplier”. 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 amplication before reaching the speaker.
Percussion tones are produced by borrowing a signal from the
upper manual 2nd harmonic drawbar, 3rd harmonic drawbar, or
both, and conducting the signal through the percussion amplier,
where its decay characteristics are controlled.
A portion 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.
1–3 MOTOR AND POWER SWITCH
The tone generator assembly, in which all tones of the
organ originate, is driven at constant speed by a self 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 ).
A toggle switch (Figure 1–1) controls power to the organ.
1–4 TONE GENERATOR
DRIVING GEAR
BAKELITE GEAR
TONE WHEELS
COIL
MAGNET
BAKELITE GEAR
COIL MAGNET
Figure 1–3: Section of Main 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 a main shaft extending along the center. Each pair of
tone wheels is mounted on a shaft and between them is a bakelite
gear held by a coil spring, forming a mechanical vibration lter (see
Figure 1–3). As the gear is not rigidly attached to the shaft, any
pair of wheels which may be stopped accidentally will not interfere
with the operation of the others.

Page 9
Figure 1–4: Block Diagram, L–100 Series
Figure 1–5: Typical Tone Generator

Page 10
Adjacent to each tone wheel is a magnetized rod with a pickup 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 necessary. Figure 1–6 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 lters for the higher frequencies.
They are not likely to need replacing. In case one lter becomes
inoperative, both the transformer and condenser must be replaced
with a matched set from the factory. Figure 1–7 shows the location
of these lters. A few frequencies use untuned lters consisting of
coils alone.
Wiring from the various lter assemblies leads to the terminal strip
on the long edge of the generator.
The output frequencies of the tone generator are numbered, for
convenience, in order of increasing frequency. The lowest, number
1, is about 32 cycles per second, and the highest, number 91,
is about 6000 cycles per second. Frequency numbers 1 to 13
are used only for the pedals; numbers 14 to 17 are omitted; and
numbers 18 to 91 are used for the manuals. Figure 1–7 showing
lter locations also shows the termination point of each frequency,
while Figure 1–5 shows typical tuned and untuned tone generators.
In case any generator frequency is weak or absent, refer to
Practical Service Suggestions for the procedure to be used in
locating and correcting the trouble.
Figure 1–6: Magnet Locations on Tone Generator