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4-3.
MIDI
Signal
Reception
Checks
By
operating the
keyboard
of
an
AX80
(or
another
MIDI
accommodating
synthesizer) that
has
been connected
onto Sampler "S612'\ check
to
assure the
channel
indi-
cator
LED
for
MIDI-CH
to
glow
more
birghtly as
Sam-
pler receives a
MIDI
signal.
When
the
channel
indicator
for
MIDI-CH
fails
to
be
made
brighter,
check by
following the
steps
below.
1)
Connect an
oscilloscope
onto IC4
pin
2 within
Main
PCB.
2)
IC4
pin 2
should normally be
at
an
"H"
level.
3)
Push
the
AX80
keyboard
keys,
and
observe
the
re-
ceived
MIDI
signal
waveforms.
(See
Fig.
4-4)
A.
When
no
MIDI
Signal
is
observed:
Check
IC1
and
PHI
in
the
MIDI
signal receiver
(MIDI
PCB).
Fig.
4-4
'o°
0
°ol
MIDI
IN
PHI
U
V
vf
\
MIDI
PCB
.
NORMALLY
AT "H
LEVEL
.
WHEN
RECEVIVING
l
SEE FIG4-4
Fig.
4-5
B.
When MIDI
Signal
is
observed but
MIDI
Indicator
fails
to
glow
more
brightly:
Check
the
MIDI-CH
indicator driving
circuit.
(See
Fig.
4-6)
e
o
c
_
_
O
R
0
rj
o
o
o
o
o
A
Q
c
o
o
o
A
4
i
4
1
i
~r
1
*7
f
A
1
A
Is
T
MAIN PCB
TRI
2SAI3I7
(T,U)
•M
1
/
/•
Dll
HZ3FA-A2
MIDI
PCB
Fig.
4-6 Indicator
Driving
Circuit
4-4.
Operationaly
Checks on
Operating
Buttons. (See
Fig.
4-7)
Check
to
assure
IC41
pins 12
to
25 on
Main
PCB
to
be
at
an
"H"
level
(5
VDC)
in
a
normal mode.
1)
When
Sampler
fails
to
operate
despite
IC41
pins 12
to
25
at
an
"H"
level in
a
normal mode,
replace
IC41.
i
i
.
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ILOADI
[KEY
TRANSl
IMANUAL
SPLICEl
[newI
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ICHANNEL
DOWN
ICHANNEL
UPl
MAIN PCB
OPERATION PCB
Fig.
4-7 Operation Button Input Circuit
4-5.
Operationaly
Check
on
VR
(Control) Inputs
1)
When
all
the
VRs
have been
set at
their
minimum
po-
sitions,
IC58
pins
1
to
5
and
26
to
28 within
Main
PCB
should be
at
an
"L"
level (0
VDC).
2)
By
operating the
VRs,
check
to
assure the
DC
levels at
IC58
pins
1
to 5
and
26
to
28
to
rise
in
correspon-
dence
with
the
VR
positions,
and
to
reach
an
"H"
le-
vel
(5
VDC)
as the
VRs
have been
set
at their
maxi-
mum
positions. (See
Fig.
4-8)
Pt2
I
I
4104
OPERATION
PCB
PL
ICE)
VOLUME
t'l)
PCB
VOLUME
(2)
PCB
MAIM
pro
Fie.
4-8
Operating
Volum
Input
Circuit
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