Hammond M Series User manual

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INGLUDINe
PARTS LIST
H000-006059
CAUTION
SEE SAFETY NOTICE ON
INSIDE COVER SHEET
ORGAN SERVICE COMPANY
6475 JOLIET ROAD SUITE B-t
LaGRANGE ILLINOIS 60525
PHONE [phone]

SAFETY NOTICE
Great care has bean taken In the design and manufacture of this product to assure that no
shock hazard exists on any exposed metal parts. Internal service operations can expose the
technician to hazardous line voltages and accidentally cause these voltages to appear on
exposed metal parts during repair or reassembly of product components. To prevent this, work
on these products should oniy be performed by those who are thoroughly familiar with the
precautions necessary when working on this type of equipment.
To protect the user, It Is required that all enclosure parts and safety Interlocks be rettored to
their original condition and the following tests be performed before returning the product to
the owner aftor any service operation.
Plug the AC iine cord directiy Into aline voltage AC receptacle (do not use an Isolation
transformer for this test) and turn the product on. Connect the network (as shown below) In
senes with all exposed metal parts and aKnown earth ground such as awater pipe or conduit.
Use an AC VOM of 5,000 ohms per volt or higher sensitivity to measure the voltage drop across
the network. Move the network connection to each exposed metal part (metal chassis, screw
heads, knobs and control shafts, escutcheon, etc.) and measure the voltage drop across the
network. Reverse the line plug and repeat the measurements. Any reading of 4volts RMS or
more is excessive and indicates a potential shock hazard which must be corrected before
returning the product to the user.
n
TEST
PROBE
VOM
AC SCALE
IOK
I I
.01 Mf
CERAMIC RF
BYPASS CAP
TEST CLIPS
CONNECTEQ TO WQWN
EARTK ORQUHO
TO EXPOSED HETAL PARTS

TABLE OF CONTENTS
PAGE PAGE
GENERAL DESCRIPTION
INSTALLATION AND MAINTENANCE
MUSICAL TERMS
NOTES AND OCTAVES
HABMONICS OR OVERTONES
ONE KEY DOES NOT PLAY 19
ONE NOTE IS WEAX 20
PERCUSSION NOTES VEAK 2I
PEDAL NOTE SOUNDS AT FULL VOLUME 21
PEDAL NOTE SOUNDS FAINTLY 21
BOW THE ORGAN WORKS HUM 21
CONSTRUCTION AND OPERATION OF COMPONENTS 7
MOTORS AND POWER SWITCHES 7
TONE GENERATOR
MANUALS 8
HARMONIC DRAWBARS 9
PEDAL DRAWBAR 9
PEDAL KEYBOAIU) 9
EXPRESSION PEDAL 10
CONTROL TABLETS 10
PERCUSSION CONTROL TABS 10
VIBRATO TABS 11
+
PRESET TABS 12
REVERBERATION-VOLUME SOFT TABS ,,.12
AMPLIFIER ASSEMBLY 12
MANUAL SECTION OF AMPLIFIER 13
PEDAL SECTION OF AMPLIFIER I
A
INTERMEDIATE SECTION OF AMPLIFIER 15
OUTPUT SECTION OF AMPLIFIER ,.,. 15
PERCUSSION SECTION OF AMPLIFIER 16
POWER SUPPLY 17
TUBE SOCKET VOLTAGES H
REVERBERATION AMPLIFIER 17
SPECIAL EQUIPMENT 18
RADIO, PHONOGRAPH, OR MICROPHONE 18
EXTENSION SPEAKER 18
EAR PHONES IS
SPECIAL POV,^R SOURCES 19
PRACTICAL SERVICE SUGGESTIONS 19
ORGAN DOES NOT PLAY 19
REPLACING TUBES 22
PROCEDURE FOR REMOVING PARTS 22
UPPER MANUAL KEY 22
LOWER MANUAL KEY 22
DRAWBAR CONTACT SPRING 23
DRAWBAR OR DRAWBAR KNOB 23
UPPER MANUAL 24
LOWER MANUAL 25
CONTROL PANEL ACCESS 26
PERCUSSION SWITCH ACCESS 26
GENERATOR 26
STARTING MOTOR 26
PILOT LIGHT 26
TAB SWITCH 26A
VIBRATO LINE BOX 26A
PEDAL KEYBOARD 26A
EXPRESSION PEDAL 26A
PRESET PERCUSSION UNIT 77
SELECTOR SWITCH 78
HARMONIC BUSBAR SWITCHING &REIT- SPLIT 78
UPPER MANUAL 78
MODE SWITCH 79
FREQUENCY DIVIDER 79
CYMBAL AND BRUSH 80
BRUSH KEi'ING 80
.CYMBAL KEYING 80
CXMBAL-BRUSH AMPLIFIER AND NOISE GATE 80
CH.\NnES AM REVISIONS 81
IiKTALLr\TION AND MAINTENANCE BACK COVER
1

LIST OF FIGURES AND ILLUSTRATIONS
FIGURE PAGE
1
.
Front View of Console -Model M27
2. Front View of Console -Model M-2 28
3. Back View of Console -Model M, M-2 29
4. Front View of Console -Model M-3 30
5. Back View of Console -Model M-3 31
6. Front View of Console -Model M-lOO 32
7. Back View of Console -Model M-lOO 33
8. Block Diagram -Model M." 34
9
.
Block Diagram -Model M-2 34
10. ,Block Diagram -Mcdel M-3 35
11. Block Diagram -Model M-lOO 35
12. Typical Tone Generator 36
13. Magnet Locations on Tone Generator .,,. 36
14
.
Generator Cover -Model M37
14A. Generator Cover -Model M-Serial 15083 and Up 37
15. Generator Cover -Model M, M-2, M-3 38
16
.
Generator Cover -Model M-3 -90485 and above 39
17. Generator Cover -Model M-lOO 40
18. Manual Wiring Chart 41
19. Drawbar Assembly 42
20. Pedal Keyboard Assembly -M, M-2, M-3 42
21. Pedal Keyboard Assembly -M-lOO 43
22. Fundamental Vibrato System -M43
23. Vibrato System -Model M -13509 and below 44
24. Vibrato System -Model M-13509 and above 44
25. Fundamental Vibrato System -M-2, M-3 45

LIST OF FIGURES AND ILLUSTRATIONS CONTINUED
FIGURE PAGE
26. Fundamental Vibrato System -M-lOO 46
27. Vibrato Line Box-Model M, M-2 46
28. Vibrato Line Box -M-3 47
29. Vibrato Line Box -M-lOO 47
30. Vibrato Scanner 47
31. Vibrato System M-2 -Serial 19000 to 22253 48
32. Vibrato System M-2 -Serial 25254 and above 48
33. Manual Hold Down Screws (M, M-2, M-3) 49
34. Pictorial -Model MAmplifier 50
35. Pictorial -Model M Amp. -Serial 8411 and above 51
36. Pictorial -Model M-2 Amp. Serial 19000 and above 52
36A. Pictorial -Model M-3 Amp (Partial) 53
36B. Pictorial -Model M-3 Amp 54
37. Schematic AO-35 Reverberation Amp M-lOO 55
38. Schematic AO-44 Reverberation Amp M-lOO 56
38A. Schematic AO-44 -See Serial Numbers 57
39. Schematic AO-66 Reverberation Amp (Later Model M-lOO) 58
40. Schematic Model M 59
41. Wiring Diagram Model M60
41A. Wiring Diagram Model M-Serial 15083 and above 61
42. Schematic Model M-2 -19000 and above 62
43. Wiring Diagram Model M-2 -Serial 19000 and above 63
43A. Wiring Diagram Model M-2 -Serial 25254 and above 64
44. Schematic Model M-3 65
F
44A. Schematic Model M-3 Serial 90485 and above 66
44B. Schematic Model M-3 -Serial 109466 and above 67
45. Wiring Diagram Model M-3 68

LIST OF FIGURES AND ILLUSTRATIONS CONTINUED
FIGURE PAGE
45A. Wiring Diagrams Model M-3 -Serial 90485 and above 69
46. Schematic Model M-lOO with AO-35 and AO-29 70
47- Schematic Model M-lOO with AO-44 and AO-29 71
48. Schematic Model M-lOO with AO-66 and AO-67 72
49. Wiring Diagram M-lOO with AO-35 Amp 73
50
.
Wiring Diagram M-lOO with AO-44 Amp 74
51. Wiring Diagram M-lOO Control Panel ,73
i
M-IOOA SUPPLEMENT
52. M-IOOA Percussion Kit Wiring Diagram 82
53. Brush and Cymbal Wiring Diagram with AO-66 Amp 83
54. Brush and Cymbal Wiring Diagram with AO-44 Amp °^
55. Schematic -Percussion Preset Unit 85
56. Schematic Diagram Model M-IOOA 87
57
.
Wiring Diagram Model M-IOOA 88
58. Percussion Kit Circuit Board Component Layout 89
4

GENERAL DESCRIPTION
The Hammond Organ "m" Series Spinet Consoles are completely self contained, re-
quiring no external tone cabinet. All Models have two (2) manuals of forty-four
(44) keys each, a12 (M, M-2, M-3) or 13 (M-lOO) note pedal keyboard, and an ex-
pression (or swell) pedal for controlling the volume. All tones are produced
by electro-magnetic tone generators and electrically amplified. Selection of tone
colors is made by adjusting eighteen(18) drawbars, and other characteristics of
the music are adjusted by means of tilting control tablets and tab switches. A
push button and atoggle switch or two toggle switches located in the front of
the Console are used to turn on the organ.
Figures 1thru 7show the front and rear views of the "M" Series Models- The
rear views are shown with the dust covers removed. Console rear panels are an
optional accessory and are not shown.
INSTALLATION AND MAINTENANCE
Acard packed with the playing instructions or located in the bench gives full in-
formation on installing the organ, oiling, and packing for moving or shipment.
(See Back Cover) MUSICAL TERMS
The service man who has had no musical training will find the following infor-
mation helpful in studying the operation of the organ.
NOTES AND OCTAVES
Keyboard instruments are divided into '^octaves" of 12 keys or notes, each with
spven (7) ''naturals" (white keys) and five (5) "sharps" or "flats" (black keys)
in adefinite sequence. Black keys occur in groups of two and three in each
octave and offer aconvenient way to identify the notes of the octave. Techni-
cally there is no difference between ablack key and awhite one, since each key
has afrequency 1.059 times the frequency of the next one below it.
Each note has afrequency exactly one half that of the corresponding note in the
next higher octave. Each white key is called by aletter for Ato G and these
letters are known as "note of the musical scale", A black key may be called a
"sharp"of the notes below it or a'^flat" of the notes above it; for instance, the
black key between Cand Dmay properly be called Cif (Sharp) or D*^ (D flat).
HARMONICS OR OVERTONES
Any musical note has adefinite fundamental pitch or frequency and also acertain
"tone quality" or "timbre" depending on its wave shape. Acomplex note is one
which includes not only afundamental frequency but also one or more "harmonics"
or "overtones," each of which is an integral multiple of the fundamental frequency.
Such acombination is more pleasing musically than anote having only asingle
frequency. The ear does not distinguish the harmonics independently ,but instead
identifies the note as acomplex tone having the pitch of the lowest component, .
or fundamental
.
HOW THE ORGAN WORKS
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 diagrams in Figures 8thru 11 show the chief components of the instru-
ments.

Electrical impulses of various frequencies are produced in the "tone generator'^
which contains anumber of "tone wheels" driven at predetermined speeds by a
motor and gear arrangement. Each tone wheel is asteel disc similar to agear^
with high and low spots, or teeth, on its edge (see figure 12). As the wheel
rotates these teeth pass near apermanent magnet, and the resulring variations
in the magnetic field induce avoltage in acoil 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 fundament
al and eight 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. The M-lOO Console has several preset tabs which make sever-
al pre-selected tones available,
MODEL M
Mixed tones from the manuals are amplified and then pass through the vibrato
mechanism, the expression control, and additional stages of amplification before
reaching the loudspeaker -
MODEL M-2i M-3i M-lOO
Mixed tones from either the upper or the lower manual may go through either the
"vibrato" channel or the "No Vibrato" channel, depending on the position of the
corresponding vibrato selector of "Vibrato Cancel" tabs. (The upper manual is
called "Solo" on the selector tab of the M-2 and M-3 to indicate that it is
best suited for playing melody or solo parts of the music.) The tones are then
combined and passed through the expression control and additional stages of
amplification before reaching the speaker(s)-
MODEL M-3» M-lOO
Percussion tones are produced by borrowing asignal from the upper manual 2nd
harmonic drawbar, 3rd harmonic drawbar, or both, amplifying it, returning part
of the signal to the same drawbar, and conducting the balance of the signal
through push-pull control tubes where its decay characteristics are controlled.
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 bus bar.
The pedal tones do not require drawbars for tone color variation, because they
are produced as complex tones by special tone wheels. From the pedals these
tones go to apedal amplifier, where the attack and decay characteristics are
controlled. The single pedal drawbar adjusts the volume of the pedals relative
to that of the manuals, and the pedal signal than is combined with the signal
from the manual before passing through the expression control, but after the
vibrato system.

CONSTRUCTION AND OPERATION OF COMPONENTS
In reviewing this section refer to the schematic circuits of the entire organ
systems in the back of this manual. Connections between components are shown in
the wiring diagrams and control assembly wiring drawings, also in the back of the
manual,
MOTORS AND POWER SWITCHES
The tone generator assembly in which all tones of the organ originate, is
driven at constant speed by asynchronous motor, located at the left side as you
look in at the back of the Console. Attached to it is the vibrato scanner. As
the synchronous motor is not self-starting, it must be brought up to speed by
astarting motor at the opposite end of the generator.
The procedure for turning on the organ is as follows: Push the "start'' switch
up (M-3, M-lOO) or in (M, M-2) and hold it for approximately eight seconds.
This allows time for the starting motor to bring the generator up to slightly
above it synchronous speed- While still holding the "start" switch, push the
"run" switch upward to its "on" position. This turns on the synchronous motor
and at the same time introduc,es aresistor in series with the starting motor
to reduce its power- Hold the "start" switch about four seconds longer and then
release it-
During this time the braking action of the synchronous motor, together with the
reduction in power of the starting motor, brings the system to synchronous
speed so that the synchronous motor can carry the load.
To turn off the. organ, push the "run" switch downward to the "off" position.
a
TONE GENERATOR
All tones of the organ originate as electrical signals in the tone generator
assembly. The M, M-2 and M-3 contains 85 tone wheels while the M-lOO has 87,
Each of these wheels has various numbers of teeth, with suitable gears for driv-
ing them at various speeds from amain shaft extending along the center. Each
pair of tone wheels is mounted on ashaft and between them is abakelite gear
held between two coil springs, forming amechanical vibration filter. 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.
Adjacent to each tone wheel is amagnetized rod with apick-up 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 13 shows where to find the magnet for any frequency number. In this
drawing 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 transformers and
condenser must be replaced with amatched set from the factory. Figures 14,
15 »16 and 17 show the locations of these filters on the indicated models. A
few frequencies use untuned filters consisting of coils alone.

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 1to 12 (1 to 13 on M-lOO) are used for pedals; numbers 13 to 17 (14 to
17 on M-lOO) are omitted; and numbers 18 to 91 are used for the manuals.
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.
The output terminals of the generator consist of solder lugs mounted on the fil-
ter transformers, to which the manual cable and pedals are connected* The fre-
quency numbers of all terminals are indicated in Figures 14, 15, 16 and 17.
MANUALS
Musical frequencies from the tone generator go through the manual cable to term-
inal strips on the two manuals and from them to the key contact springs-
Each of the two manuals has forty-four (44) playing keys, or approximately
3-1/2 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 har-
monics of that key) which touch an equal number of busbars when the key is press-
ed, (Some keys at the right end of each manual have fewer springs, as noted be-
low) -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
(shown in Figures 3, 5,7) is provided in each manual to slide the busbars end-
wise and thus provide afresh contact surface.
The busbar shifting mechanism is somewhat different on the M-lOO than on prior
models of the Hammond Orgam Models M, M-2 and M-3. Looking under the lower man-
ual on the left hand end, 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 pliers or ahook, this
tongue can be moved in and out and it in turn moves the busbars. The upper man-
ual shifter is in a similar place, but requires removal of the generator dust
cover to gain access to it.
The key contacts are connected through resistance wires to the manual terminal
strips. The manual wiring chart Figure 18, shows how the contact 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,
inasmuch as the highest harmonics of the highest keys are above the range of the
tone generator and are not required. Since the percussion control tubes in the
M-3 and M-lOO are 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 harmonic drawbars for that manual in the M, M-2, M-3 and through the "Draw-
bars" tab in the M-IOO-
8

HARMONIC DRAWBARS
The left group of eight (8) harmonic drawbars (Figure 19) is associated with the
lower manual, and the right group of nine (9) drawbars controls the upper manual.
By sliding these drawbars in and out, the organist is able to mix the fundamen^
tal and harmonics (or overtones) in various porportions. The distance abar is
pulled out determines the strength of the corresponding harmonic; and if adraw-
bar is set all the way in, the harmonic it represents is not present in the
mixture. Neither manual will play unless at least one of its drawbars is pulled
out at least part of the way in the case of the M, M-2, M-3, or with the "Draw-
bars^' tab pressed or preset tab pressed in the M-100.
The drawbars slide over nine (9) busbars ,representing intensity levels, and
each drawbar has two contacts connected together by aone ohm resistor. As the
drawbar moves, at least one of the contacts is touching some busbar at all times,
and therefore there is no "dead spot" in the drawbar motion. The one ohm re-
sistor avoids an actual short circuit between adjacent busbars. These busbars
extend the length of the drawbar assembly but are split in the middle to form
two groups of nine (9)- Those in the left group, under the lower manual draw*
bars, are connected to low impedance primary taps on the lower manual matching
transformer. Similarly, those in the right group, under the upper manual
drawbars, are connected to taps on the upper manual matching transformer- Sig-
nals from the high impedance secondaries of these two transformers go through
the lower manual "Vibrato Cancel" and upper manual "Vibrato Cancel" tabs to the
apraplif ier input terminals -
PEDAL DRAWBAR
The 12 (M, M-2, M-3) or 13 (M-100) playing pedals are operated by the left foot
and are connected to the lowest 12 or 13 frequencies of the generator. The
center drawbar adjusts the volume of the pedals. It operates avariable con-
denser (shown in Figures 3, 5, and 7) which is connected to the pedal section
of the amplifier. For operation of the circuit see description of "amplifier,"
PEDAL KEYBOARD
The 13 playing pedals are operated by the left foot and are connected to the
lowest 13 frequencies of the generator. Like the manuals, they have light and
dark keys arranged in the standard octave pattern. Figures 20 and 21 identifies
the pedals and shows the generator frequency number associated with each.
A"pedal contact" on each pedal opens when the pedal is pressed, thereby allow-
ing the correct generator frequency to reach the amplifier. In addition there is
a"pedal keying contact'' for all pedals, which closes when any pedal is operated.
It serves to key the pedal amplifier, causing the note to sound at the desired
rate-
When apedal is pressed its "pedal contact" opens first, selecting the correct
note. Immediately the "pedal keying contact" closes, causing the note to sound.
When the pedal is released amechanical latch keeps the "pedal contact" open,
so that the last-played pedal note continues to sound for alength of time de-
termined by the position of the pedal "Fast Decay" and "Pedal Legato" tabs in
the M-100. In the M, M-2, and M-3; the time which the pedal sound is heard is
determined by the setting of the "Pedal Decay" tablet and a"Pedal sustaining
control" attached to the expression control. The electrical operation of these
circuits is described under "amplifier"-
9

EXPRESSION PEDAL
The "expression" pedal, sometimes called "swell" pedal (Figures 1,2, 4, and 6)
is operated by the player's right foot and varies the volume of both manuals
and pedals together. It is connected mechanically to a special variable air
condenser mounted on the amplifier. When the pedal is tilted back (closed)
by pushing on the player's heel the music is softest, and when pushed forward
(opened) by Che player's toe the music is loudest-
In the M, M-2, and M-3, attached to the expression pedal is a"pedal sustain-
ing control" lever, which is operated by sliding the foot sldewlse on the
pedal. If this lever is not pressed, each pedal note dies away rapidly or
slowly, depending on the setting of the "pedal decay" tablet. If the lever
is pressed to the left, the last-played pedal note dies away much more slowly,
CONTROL TABLETS
The Model M has 6, while the M-2 and M-3 have 7of these control tablets and
each has two positions (figures 1, 2and 4). The "volume" tablet changes the
overall volume and thus supplements the expression pedal. The "pedal attack"
tablet determines how fast apedal note sounds after apedal is depressed, and
"pedal decay" determines how fast the sound dies away after the pedal is re-
leased.
The "vibrato lower manual" and "vibrato solo manual" tablets turn the vibrato
effect on and off independently on the lower and upper manuals respectively.
The next tablet provides achoice of "normal vibrato" or "vibrato chorus"
(it is effective only when the vibrato effect is on). The last tablet can
be set for "small" or "normal" vibrato to adjust the extent of the pitch vari-
ation provided by the vibrato mechanism,
The M-lOO has 24 tabs, each providing some change in the instruments operation.
To have the instrument sound after turning 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.
PERCUSSION CONTROL TABLETS
The M-3 and the M-lOO are the only two Models which contain percussion and each
unit has four (4) associated tabs.
In the M-lOO, these tabs operate only when the upper manual "Drawbars" tab
is pressed. Pressing either "Second Harmonic" or "Third Harmonic" will, when
the Upper manual is played, cause the tone to sound percussively (in addition
to sustained organ tones). Both tabs can be pressed, giving acombination per-
cussive tone, "Fast Decay" causes the percussive tones to fade away with
greater rapidity- "Percussion Soft" reduces the volume for the percussive
signal.
In the M-3, when the "Percussion" on-off tablet is "On", the Solo (Upper) man-
ual will play 2nd or 3rd harmonic tones percussively (in addition to the sus-
tained organ tones). The "Volume" tablet in "Normal" position allows the per
cussion tones to soilnd percussively as with the M-lOO and reduces the level
of the Solo manual sustained organ tones to maintain proper balance between
the manuals. In "Soft" position it allows the percussion tones to sound
only softly and restores the full level of the Solo manual sustained organ
tones. The "Decay" tablet determines how fast the percussion tones fade
away when the Solo manual key is pressed.
10

Operation of the electrical circuits associated with the percussion feature
are described in the percussion section of the amplifier theory.
VIBRATO TABLETS
The Model Mvibrato uses three control tabs- Two degrees of vibrato are
available with the "amount of Vibrato" tablet and the "Vibrato Chorus". A
third tablet marked "Vibrato" turns the effect on or off.
The M-'2, M-3, and M-lOO have aselective vibrato system, using four (4) con-
trol tablets to vary the vibrato effect. On the M-lOO series only, an addit-
ional stop (Vibrato Cancel) to the right of the preset tabs permits any
Vibrato effect to be cancelled immediately.
The vibrato effect is created by aperiodic raising and lowering of pitch,
and thus is fundamentally different from atremolo, or loudness variation.
It is comparable to the effect produced when aviolinist moves his finger back
and forth on astring while playing, varying the frequency while maintaining
constant volume.
The Hammond Vibrato equipment (See Fundamental Diagram of Vibrato System,
Figures 22, 25,26) varies the frequency of all tones (excepting the pedal and
percussive tones) by continuously shifting their phase. It includes aphase
shift network or electrical time delay line, composed of anumber of low pass
filter sections, and acapacity type pickup or scanner, which is motor driven
so that it scans back and forth along the line.
Electrical waves fed into the line are shifted in phase by each line section
(the amount per section being proportional to frequency), so that at any tap of
the line the phase is retarded relative to the previous tap
•
The scanning pickup traveling along the line will thus encounter waves increas^
ingly retarded in phase at each successive tap. As ashift in phase is equiva-
lent to an instantaneous change in frequency, the continuous change in phase
becomes acontinuous frequency variation. Since the scanner sweeps from start
to end of the line and then back, it alternately raises and lowers the output
frequency, the average remaining equal to the input frequency.
The exact amount of frequency shift depends not only on the amount of phase
shift in the line but also on the scanning rate. This rate, however, is constant
because the scanner is driven by the synchronous running motor of the organ.
In the M, M-2, and M-3, the "Amount of Vibrato" tablet varies the amount of
frequency shift by causing the whole line to be scanned for "Normal Vibrato"
and only one fourth of it for "Small Vibrato".
In the M-lOO, the "Vibrato Small" Tablet varies the amount of frequency shift
by causing two thirds of the line to be scanned, in contrast to the entire
line when in the up position.
Avibrato chorus effect, similar to the effect of two or three slightly out-of-
tune frequencies mixed together, is obtained when the vibrato output signal
is mixed with aportion of signal without vibrato. This is accomplished by the
"Vibrato Chorus" tab, which causes only part of the Incoming signal to appear
across the vibrato line and the rest across aresistor in series with the line-
As the vibrato effect is applied to the part of the signal appearing across the
line but not to the part appearing across the resistor, the combination pro-
duces achorus effect -
11

In the M-lOO, aCeleste effect is obtainable by the use ''Vibrato Celeste I"
and "Vibrato Celeste II" tabs. These can be used independently or together.
Use of these tabs introduces aresistor network at the far end of the Vibrato
line, changing the termination impedance. This in turn causes areflective
signal to appear in the line, which is picked up by the scanner.
In the Model M, to remove the vibrato effect entirely, the 'Vibrato" tablet
in "off" position places avery large resistor in series with the vibrato
line. Practically all of the signal appears across this resistor and the
vibrato effect is virtually eliminated. Acompensation circuit consisting of
Rl and CI maintains constant volume by introducing negative feedback with the
"vibrato" tablet "off". (See Figures 23 and 24).
Figures 23 thru 26 show only the "Vibrato" channel of the amplifier. All tones
sent through this channel have the vibrato effect. In the M-lOO, when vibrato
is not desired on one manual or both, the "Vibrato Cancel" tabs in the down
position feed their signals through the "no Vibrato" channel of the amplifier.
Figures 27, 28 and 29 show the vibrato line box. See figures 3, 5, and 7for
location of line box.
The scanner is mounted on the synchronous motor and driven at 412 revolutions
per minute- It is amulti-pole variable condenser with 16 sets of stationary
plates and arotor whose plates mesh with the stationary ones. Figure 30
shows the construction of the scanner ,with two sets of plates removed to show
the rotor-
Signals coming from the vibrato line appear on the stationary plates and are
picked up, one at atime, by the rotor. Connection to the rotor is made by
carbon brushes as shown in Figure 30. Two brushes touch the sides of the con-
tact pin and athird presses on the end, in order to eliminate the possibility
of contact failure.
The complete electrical circuit of the vibrato system is shown in the schematic
diagrams contained in the back of this manual-
PRESET TABS CM- 100)
Four tabs are provided for each manual. As indicated, they provide achoice of
using the drawbars or playing the preset tones indicated on them.
REVERBERATION AND VOLUME SOFT TABS CM- 100)
Several degrees of reverberation are obtained by the use of either or both tabs
labeled ''Reverberation I" and "Reverberation II", These tabs in addition to
turning this feature on, govern the loudness or amount of reverberation by are-
sistive network used in conjunction with the speaker. The "Volume Soft" tab
controls the overall volume of the organ and is especially useful where playing
might disturb others
.
AMPLIFIER ASSEMBLY
In the Mand M-2 models, the amplifier assembly is on asingle chassis, but is
actually composed of four sections: Manual, Pedal, Intermediate, and Output ,as
indicated in the block diagrams, figures 8and 9, and in the schematics in the
schematic section of this manual.
12

In the M-3 and M-lOO models there is one additional section, the percussion
amplifier. The block diagrams appear in Figures 10 and 11,
The M-lOO model alone has one additional amplifier assembly, the Reverberation
Amplifier. This separate amplifier is used to secure the Reverberation effect
in conjunction with the Reverberation unit. This amplifier has its own speaker,
MANUAL SECTION OF AMPLIFIER MODEL M
The manual section, composed of tubes VI and VZ, receives its signal from the
matching transformer Tl. The "special input" jack, connected through anet--
work to the cathode of VI, provides alow impedance input circuit (see "Special
Equipment")* Some treble attenuation is provided by afeedback network con^
sisting of C2, R2, and R3, connected from cathode follower tube V2 to the in-
put of VI, The output signal obtained from the cathode of V2 drives the vibrato
line (see "Vibrato system") and the manual signal, after passing through the
vibrato system, is combined with the pedal signal at the grid of V3.
MODEL M-2» M-3
The manual section is composed of two channels connected to the "Vibrato" and
"no Vibrato" input terminals. Either of the two matching transformers can
feed asignal into either input channel, depending on whether the correspond-
ing control tablet is set for Vibrato "on" or "off".
Signals entering the "no Vibrato" channel (tube V2) are amplified and fed
directly into the intermediate section of the amplifier while signals going
into the "Vibrato" channel (tubes VI and V3) pass through the Vibrato system
first- The output signal of the Vibrato system is combined with the "no Vi-
brato", Percussion^ and Pedal signals at the grid of the intermediate ampli-
fier.
Suitable tonal balance is secured in the "no Vibrato" channel by afeedback
network connected from plate to grid of V2. Similar tonal balance is provided
in the "Vibrato" channel by afeedback network connected from cathode follower
V3 to the gird of VI- The two channels are matched by selecting R27 (M-3), and
R20 (M-2) at the factory-
M-100
The manual section is composed of two channels connected to the "Vibrato" and
"no Vibrato" input terminals- Either of the two matching transformers can feed
asignal into either input channel, depending on whether the corresponding con-
trol tablet is set for vibrato "on" or "off".
Signals entering the "no Vibrato" channel (tube V2) are amplified and fed dir-
ectly into the intermediate section of the amplifier, while signals going into
the "Vibrato" channel (tubes VI and V3) pass through the Vibrato system first.
The output signal of the Vibrato system is combined with the "no Vibrato" and
pedal signals at the grid of the intermediate amplifier.
Suitable tonal balance is secured in the "no Vibrato" channel by afeedback net-
work consisting of C6, R12, R13 and R13A connected from plate to grid of V2.
Similar tonal balance is provided in the "Vibrato" channel by afeedback network
including CI, Rl, R2, and R2A connected from cathode follower V3 to the input
of VI. The two channels are matched by selecting R20 at the factory.
13

PEDAL SECTION OF AMPLIFIER -Mi M-2i M-3
The pedal amplifier, composed of one tube, V7, receives its signal directly from
the pedal generators. When apedal key is pressed its "pedal contact" opens,
delivering asignal voltage of the proper frequency to the grid of V7, The note
cannot sound instanly, however, because the tube is normally cut off by anega-
tive 21 volt grid bias.
Near the end of the pedal stroke the "pedal keying contact" (common to all ped-
als) closes. This shunts aresistance from the bias point to ground, discharg-
ing the bias condenser C57 and allowing the note to sound.
If "pedal attack" is at "normal" only asingle resistor R68 is placed across
the bias condenser when the pedal keying contact closes. This very quickly dis-
charges the condenser, and the note sounds quickly, although not abruptly.
In case "pedal attack" is set at "slow"^ the shunting resistor is increased by
the addition of R69 and so the bias condenser cannot discharge as quickly- It
takes an appreciable time, therefore, for the bias to drop low enough so that
the note sounds
.
When the pedal key is released, the pedal keying contact opens, allowing cutoff
bias to be applied again to the tube. With "pedal decay" set at "fast" this
occurs rapidly, since R74 charges C57 in ashort time. With "pedal decay" set
at "normal" the increased resistance delays the charging of C57 and permits the
tone to sound for alonger time.
If the "pedal sustaining control" is operated (lever on expression pedal pressed
to left), an additional resistor R76 is introduced. This delays the charging
of C57 still further and causes the note to sound for amuch longer time.
Alatching mechanism holds the last-played pedal contact open until some other
pedal is operated, in order to Insure that the correct note will sound through-
out the decay period.
The pedal cutoff adjustment R73 varies the screen voltage of the pedal ampli-
fier tube. It must be adjusted so that the pedal tone is just inaudible with
the pedal drawbar and expression pedal set in loudest position, as instructed
in "Practical Service Suggestions".
M-lOO
The pedal amplifier, composed of one tube, VIO, receives its signal directly
from the pedal generators- When apedal key is pressed its "pedal cqntact"
opens, delivering asignal voltage of the proper frequency to the grid of VIO.
+
The note cannot sound instantly, however, because the tube is normally cut
off by anegative 22 volt grid bias.
+
Near the end of the pedal stroke the "pedal keying contact" (common to all
pedals) closes. This shunts aresistance from that bias point to ground, dis
^
charging the bias condenser C57 and allowing the note to sound.
When the pedal key is released, the pedal keying contact opens, allowing cut-
off bias to be applied again to the tube. With the pedal "Fast Decay" tab de-
pressed this occurs rapidly, since R81 charges C57 in ashort time. With the
tab up, the increase resistance delays the charging of C57 and permits the tone
to sound for alonger time.
14

If the "Pedal Legato" stop Is depressed, an additional resistor R82 is introduced.
This delays the charging of C57 still further and causes the note to sound for a
much longer time.
Alatching mechanism holds the last-played pedal contact open until some other
pedal is operated, in order to insure that the correct note will sound throughout
the decay period.
The "Bass Mute" tab varies afiltering circuit in the VIO tube output so the
higher frequencies are bypassed to ground, giving adeeper tone to the pedals.
The pedal cutoff adjustment R85 varies Che bias voltage of the pedal amplifier
tube. It must be adjusted so that the pedal tone is just inuadible with the pedal
drawbar and expression pedal set in loudest position, as instructed in "Practical-
Service Suggestions.
"
To prevent apedal note from sounding when the organ is first turned on, are-
sistance of five ohms inserted in series with the heater of the pedal amplifier
tube lengthens its warm-up time so that the cutoff bias is applied before the
tube is conductive.
INTERMEDIATE SECTION OF AMPLIFIER
From the plate of the pedal amplifier tube the pedal signal passes through a
variable air condenser (operated by the pedal drawbar) to the intermediate
amplifier (half of V3)(M), V4 (M-2, M-3, M-lOO) .At this point the pedal signal
is mixed with the vibrato, non-vibrato, and percussion signals from the manuals
(M-3, M-lOO).
Depressing the "Volume Soft" tab reduces the overall volume of both manuals
and pedals by shunting asmall condenser across the input of the intermediate
amplifier. At the same time it provides pedal compensation by adding R65 in
series with the pedal generators and thereby increasing the relative volume
of the pedals-
The small feedback condenser from plate to grid of the intermediate amplifier
is a means of increasing the effective input capacity of the tube. In this cir-
cuit the effective input capacity is this value multiplied by the amplification
factor of the tube, or atotal of about 1500 micromicrof arads ,This provides
asuitable load for the output of the scanner and the pedal drawbar,
The combined manual and pedal signals go through the intermediate amplifier
to the expression control (operated by the expression pedal), which is aspecial
variable air condenser with asingle set of movable plates and two sets of
stationary plates. With the expression pedal in "loud" position the signal is
transitted directly to the grid of the following tube, while in "soft" position
the signal goes through atone^compensated attenuating network. At inter-
mediate positions the signal is obtained from both sources, providing con-
tinuously variable control,
OUTPUT SECTION QF AMPLIFIER (M)
V4 is acommon-cathode-impedance phase inverter driving push-pull output tubes
V5 and V6* The second grid of V4 provides aradio-phonograph input channel (see
"Special Equipment"). Asmall feedback condenser from voice coil to grid of V4
makes the pedal response more uniform by reducing speaker resonance. (In model
Mconsoles below serial number 3000, with amplifiers marked type M-A, this feed-
back connection is not used; C46 is omitted, C37 is omitted, C42 is .00135 mfd,,
15

and T2 does not have asecondary center tap)
M-2i M-3
The second half of V3 is aphase inverter driving push-pull output tubes V5 and
V6. Asmall feedback condenser C22 Cm-2), C23 (M-3) from voice coil to grid of
V4 makes the pedal response more uniform by reducing speaker resonance. This
condenser (located in the expression control unit) is variable and is adjusted
at the factory.
M-lOO
The second half of V3 is aphase inverted driving push-pull input tubes V5 and
V6, which in turn drive two 16 ohm speakers connected in parallel, Asmall
feedback condenser C23 from output transformer secondary to grid of V4 makes
the pedal response more uniform by reducing speaker resonance. This condenser
(located in the expression control unit) is variable and is adjusted at the
factory.
PERCUSSION SECTION OF AMPLIFIER
The 2nd or 3rd harmonic signal (M-3) or both (M-lOO) (depending on position of
the harmonic selector tabs) is conducted through the percussion matching trans-
former and amplified by tube V7. The resistive feedback on this tube provides
proper loading on the matching transformer to fix the primary impedance at
about 5ohms. This provides avolume compensating effect so that the per-
cussion output signal is about the same whether one key or several are played.
Besides providing push-pull signal for the control tube (V9), transformer T5
has another winding which feeds signal to the 2nd or 3rd harmonic drawbar
through equivalent key circuit resistors.
The control tube (V9) is normally conducting, so when akey is pressed the second
or third harmonic percussion signal first sounds loudly. It passes through the
control tube, transformer T6, aband pass filter network, and terminal Dto the
grid of V4,
Imrr.ediately the note begins to fade away, giving the characteristic percussion
effect. This fading Is accomplished as follows: When the percussion switch is
"on'', terminal K(normally held at plus 25 volts through anti-spark resistor
(R-53) is connected to the solo manual 6th, (8th in M-3) harmonic busbar* When a
key is pressed, terminal Kis grounded through the key contact and the tone gen-
erator filter. This virtually grounds the plate of V8 (connected as a diode),
open-circuiting the tube and isolating the control tube grid circuit. The grids
then drift from their operating potential of about plus 25 volts to acut-off pot-
ential (about plus 15 volts) at arate determined by the time required for 031 to
discharge through R59 and R60-
The percussion signal is now blocked. No percussion notes can sound until all
keys of the solo manual are released and the control grids again rise to plus 25
volts. The time of this rise (that is, how quickly the control tubes turn on again
after akey is released) is the time required to change C31 to plus 25 volts
through R57 and R58.
"^
16

When the percussion Second Harmonic" or Third Harmonic" (>i-3) or both (M-lOO)
tabs are down, the corresponding upper manual harmonic drawbars are disconnect-
ed from their lead wires and these wires (which come from the manual busbars)
are connected to the percussion matching transformer. The 6th harmonic (M^lOO)
or 8th (M^3) drawbar is also disconnected 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 push-pull control tube. Therefore, the 6th harmonic (M-lOO)
or 8th (M-3) is not available on the upper manual when the percussion is in use.
When the "Percussion Soft" tab is depressed, it reduces the volume by shunting
resistor R50 across the percussion output transformer.
The percussion "Fast Decay" tab determines how fast the sound fades away after
ak-ey is pressed. When akey is pressed with the tab up, resistor R60 dis-
charges capacitor C31, reducing the D,C. voltage on the control tube grids to
cutoff in about 2-1/2 seconds. When the tab is pushed down another resistor
is shunted across the original resistor R60, reducing the time to discharge
capacitor C31 and thereby reducing the D.C. voltage on the control tube grids
to cutoff in less than 1/2 second. To preserve about the same effective loud-
ness between "slow" and "fast" decay settings, shunt resistor R62 is disconnected
when the decay tab is in "fast" position. This reduces the effective control
tube bias and thus increases the loudness.
With the "Second Harmonic" tab depressed, the upper manual 2nd harmonic draw-
bar wire is connected to the percussion matching transformer and asignal is
fed back to the 2nd harmonic drawbar- With the "Third Harmonic" tab depressed
the upper manual 3rd harmonic drawbar wire is connected to the percussion
matching transformer and asignal is fed back to the 3rd harmonic drawbar.
Both tabs can be used at the same time in the M-lOO, however in the M-3, only
one or the other is available.
POWER SUPPLY (ALL MODELS)
The power supply uses a5U4 rectifier tube with aconventional filter circuit.
TUBE SOCKET VOLTAGES
Voltages shown on the schematics are taken with a20,000 ohm-per-volt meter.
Line variations may cause up to 20% variation in the indicated voltages.
To make tube sockets accessible, remove lever from shaft of expression unit on
amplifier; loosen cable clamp on lower shelf; remove four amplifier mounting
screws and turn amplifier upside down, being careful not to rest on expression
unit lever. The tabs and expression lever may be in any position, and no key
should be depressed unless specified,
REVERBERATION AMPLIFIER (M-lOO)
When either "Reverberation I," "Reverberation II," or both are used, the music
played will be reverberated. This reverberation signal is in addition to the
normal sound produced through the two 12" speakers connected to the main ampli^
fier •Aseparate amplifier and speaker are incorporated in the instrument for
this purpose,
Asignal from the voice coil terminals of the regular speakers in the console
goes through aresistor network and two Incandescent lamps to the drive coils
of the reverberation unit, as shown under "input to reverberation unit" in the
schema tic dia gram
.
17

The incandescent lamps are used as volume limlters or volume compression cir-
cuit. When the organ is played loudly, the lamp filaments become hot and In-
crease in resistance, and, therefore, the amount of signal furnished to Che
reverberation unit does not increase as fast as the volume of the no-rever-
berated signal. This is a desirable musical effect, since agreater proportion
of reverberated signal is needed at low volume levels.
The drive coils introduce vibration in two coil springs. These vibrations
bounce hack and forth in the coils springs to simulate natural echoes of sound,
in alarge room. Pickup coils at the other end of the two springs drive the
input of the amplifier. The amplifier output drives an 8ohm 8" speaker.
SPECIAL EaUIPMENT
RADIO. PHONOGRAPH. OR MICROPHONE
Aphonograph, radio, or microphone amplifier will play through the organ speak-
er if connected to the pin jack marked "RADIO-PHONO" located on the expression
control unit of the organ amplifier. The device should have an output level
of about 1/2 volt maximum, and must have its own volume control, as neither the
expression pedal nor the "Volume" tablet will affect it. The organ may be play-
ed at the same time.
In the Model Monly, occasionally for special effects it may be desirable to
apply vibrato to the signal from aphonograph, radio or microphone. In this
case connect to the pin jack market "SPEC-INPUT". This point has alow imped-
ance to ground (about 7000 ohms) and may conveniently be driven from the voice
coll terminals of an amplifier having alevel of about 5volts maximum. The
expression pedal, "volume" tablet, and three vibrato tablets will then be ef-
fective on the input signal just as they are on the organ music.
EXTENSION SPEAKER
An additional speaker, of the permanent magnet dynamic type, may be attached
to the organ if special circumstances make it desirable. It should be con-
nected to the two voice coil terminals on the amplifier. It is essential that
the speaker be at least 10" in diameter and be mounted in an adequate baffle
to bring out the organ pedal notes properly. The console speaker voice coil
wires may be left connected or not, as desired.
Hammond Organ tone cabinets may be used as extension speakers. Akit for mak-
ing the necessary connections can be secured from your dealer.
EAR PHONE (MONAURAL)
Ear phones may be connected to the organ if someone wishes to practice without
disturbing others. They will generally give adequate volume when connected to
the^ voice coil" terminals of the amplifier, with the speaker disconnected. A
resistor of 6to ID ohms, with power rating not less than 10 watts must be con-
nected across these terminals whenever the speaker is disconnected.
18