Hammond L series User Manual

4-19.
ONE
NOTE
IS
WEAK.
-
4-21.
FULL
VOLUME
PEDAL
CIPHER.
-
4-20.
a.
Trace
the
note
as
described
in
the
pre-
ceding
section
to see
whether
weakness
is
due to
dirty
contact,
poor
connection,
defective
filter
or
reduced
output
of
magnet
coil.
Check
at
each
point by
comparing
intensities
with
higher
and
lower
frequency
numbers.
b.
It
is
possible
that
one
or
more
notes may
be
acoustically
weak,
due
to
the
room
and
the
furnishings,
although
the
actual
signal
level is
equal
to
that
of
adjacent
notes.
This
can
be
checked
by
reading
voltages
of
the
various
notes
on
an
output
meter
connected
to
the
voice
coil
terminals
on
the
amphfier.
All notes
will
not give
equal
output,
but
voltage
should
vary
smoothly
from
note to
note.
In
this
test
variations
of
less than 30%
should
be
ignored.
c.
Each
magnet
is
set
at
the
factory
by
tapping
it
gently, with
the set
screw
partially
loosened,
while
observing
an
output
meter.
Experience
has
shown
that
the
magnets
seldom
need
adjustment
and
that
setting
them
without
proper
equipment
involves
danger
of
damaging
both
magnet and
wheel.
Therefore
it is
not
recommended
that
the
service
man
attempt
this
adjustment.
PERCUSSION NOTES WEAK,
DO
NOT
PLAY,
OR DO
NOT
DECAY
PROPERLY.
-
a. Adjust
percussion
cutoff control
with
expression pedal
wide open,
VOLUME
SOFT
tab
up, upper DRAWBARS tab
down, and
drawbars
pushed in,
THIRD
HARMONIC
tab
down, and
FAST
DECAY
tab
down. Hold
down
first C
key on upper
manual
and adjust
percus-
sion
cutoff
control
to the exact point
of cutoff or silence.
b. Check
tube
VII.
c.
Always adjust
percussion
cutoff control
after replacing VI 1
(
1
2AU7).
a.
It is
possible
to make a
black
pedal
lock
down and
play
continuously
by
striking
it
very
hard at
an
angle so
that
it
moves
sidewise
as well
as
downward.
This
will
never occur
if the pedals
are used
pro-
perly, as only
slight
pressure with
the
toe is
required
for playing.
b.
A
pedal
locked
down
in this way
will
remain
visibly
depressed
and
tilted.
It
can
be
released by
pressing it down
very
hard,
with a
slight
pressure
opposite to
the
direction
of tilt. No
permanent
damage
will result.
4-22.
HUM.
-
a.
A loud
60
cycle or
1 20 cycle
hum
in the
speaker
may
come
from
some
nearby
electrical
appliance, as
explained
on
the
instruction
card
which
accompanied
the
instrument.
It
may be
picked
up by
the
matching
transformer
or the
console
wiring.
Hum
from this source
will disap-
pear
if
you
remove the BK
plug
from
the
AO-41
chassis. It may
be
eliminated by
moving
either
the
console or
the
appliance.
b.
Any
other hum
must
originate
in the
amplifier
circuit,
and can
generally be
cured
by
replacing
one
or
more
of the
electrolytic
condensers.
c.
In case hum
originates
in either
amplifier
but is not
due
to the
electrolytic
con-
densers, its source
can be
isolated
by
successively
removing
tubes or
by
ground-
ing
successive
points in the
signal
circuit.
4-23.
REPLACING
TUBES.
-
a.
The vacuum
tubes
are
all
standard
radio
types and
can
be tested
in the usual way.
Figures
5-15
through
5-18
show
the
location
of tubes in
the
amplifier.
b.
If
tube
VI 1 is
replaced,
check
percussion
cutoff
adjustment
as
explained
in
para-
graph
4—
4h.
4-6

Hammond L series Specifications

General

Brand	Hammond
Model	L series
Category	Musical Instrument
Language	English