Hammond L series User Manual

P-P
from the pedal
keyboard
is
connected
to
the input
T4. The first
two stages
using
transistors
Ql
&
Q2
are basically
ampli-
fiers
providing
a
+
1
3 V
square
wave
pulse
for
each
input
cycle.
The first
+
1
3
V
square
wave
pulse
appearing
on
transistor
Q2
collector
turns
on
Q4
providing
a
+
1
3
V pulse
at
output
terminal Tl
1
.
At
the
same
time
C4 is
charged
through R6.
This
icharging
time is
long
enough
to
delay
the
conduction
of
Q3
until
after the
first pulse;
then
Q3
conducts,
cutting
off
Q4
before the
second
pulse
can be
passed.
Effectively,
lieach time
a signal is
applied to
the
input
at
T4,
one
pulse
appears at
the
output termi-
j
nal
(Til),
which
connects to
terminal
F
of
voice
generator
board
124-0001
14.
Ql
15
is
normally
off.
The input at
T'
is
fed
through
R
163
to
the
base
of
Ql
1
5
to
turn
the
transistor
on.
When
Ql
1
5
is
on,
the
DC
voltage
at
its
collector
drops
from +
15V
to
Zero
V.
Note
that
pin
'G'
is
jumpered
to
pin
'C,
and
that
both
are
common
to
Ql
1
5
The signal
entering pin
is
fed
through
R160
to
the base
of Ql
14,
which is
nor-
mally
in
the "on"
condition
with
no
pedal
pressed
(collector at
OV DC).
When a pedal
is
pressed, the
negative
signal
applied to
the
base
turns
"ofV Ql
14,
and
the
collector
voltage
rises
to
+
1 5
V DC.
Point
"D" is
routed to
point
"A" and
coupled
through
CI
27 and
Rl 56 to
the base
of Ql
1
2.
Ql
1
2
which
is
normally
"off
is
turned
''on",
and its
collector
voltage
drops to
zero. The
collector
signal
of
Ql
1 2 is
then
fed
to
the
base
of
PNP
Ql
13,
turning
it "on'\
and its
collector
switches
to
+
1 5
V DC. This
+
1
5
V
DC pulse
on
the
collector
of
Ql
13
is desig-
nated as
the
pedal-down
pulse,
and is
routed
through
the
BLOCK
and/or
CYMBAL tabs,
when "on" to
trigger the
selected
voices.
Output
is
obtained
as
described
in
Paragraph
2-17.

Hammond L series Specifications

General

Brand	Hammond
Model	L series
Category	Musical Instrument
Language	English