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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.
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