Roland HP 2700 Service Notes page 30

HP-3700/2700
ADJUSTMENT
An
ADC
adjustment
is
provided on the
HP- 2700
and
HP-2700> HP-3700
SmSpird:
LT
0
HP- 3700.
Perform
this
adjustment
in
the following
situations.
(1)
When you
have
exchanged
ICs.
(2)
If
as the
sound
decays, noise
is
heard immediately
before the sound disappears.
There
are
two ways
to
make adjustments
;
while watching
the waveform on an oscilloscope, and aurally while listening
to the sound.
(I).
Making
adjustments while watching the
oscilloscope
waveform
1. In test
mode,
select test
item
1.
(For the procedure,
refer to the Test
Mode
page.)
2.
Make panel settings as
follows.
VOLUME
:
MAX
BRILLIANCE
:
CENTER
3.
Connect the test point
TP2
or
TP3
on the jack board
to the oscilloscope, and
make
the following settings.
5 mV/div
2 mS/div
4. Rotate the
potentiometer VR1 on
the jack
board so
that the waveform
is
as
shown
below.
(I)
1.
-f
X
h
•
VOLUME
:
MAX
BRILLIANCE
:
Center
3.
JACK.-Jt'-
K±®xX
h •
-tt'O
t'TP2*^TP3iC;l->X
5
mV
/ div.
2 mS/div.
4.
JACK4<'-
K±®¥@^dOJ
^-AVRl^lHlL-r.
MW
TH®
J;
0 9
9.2
mS
incorrect
CORRECT
/ISS
INCORRECT/^liH
Dec.
1990
(n)Making adjustments while listening to the
sound
1.
Turn the power on, and
make
the following panel
settings.
VOLUME
MAX
BRILLIANCE BRIGHT
E.PIANO
ON
CHORUS OFF
TREMOLO OFF
REVERB OFF
2.
Softly play any key
in
the
octave above the middle
of the keyboard.
3.
While
listening
to the sound from the speaker, adjust
the potentiometer
(VRl) on the jack board. Rotate
VR1
so that the
sound
is
the clearest
(i.e.,
so that
high
frequency elements are minimized, and the
sound
is
close to a sine
wave).
NOTE
:
In the
case of the HP- 2700, you can rotate
VR1
directly from the jack board.
In
the case of the
HP- 3700, there
is a
hole
in
the jack board under VRl, allowing you to insert
a
minus screwdriver from the solder side to
make
adjustments.
(n)
VOLUME
:
MAX
BRILLIANCE
:
BRIGHT
E.PIANO
:
ON
CHORUS
:
OFF
TREMOLO
:
OFF
REVERB
:
OFF
<3i<o
3.
JACK
A-
K±®it^ll
(VRl)
VRl
LT At,
C
A
^ i C
-5
;±
:
HP-2700 ®Ji^t4. JACKd^- K®±;i'b'E®i S VRl
Hlf
HP-3700 ®Ii^(4, JACKd^'- K®VRl®T#ltdA4i<PI>.'
lAAPSI-r-Bo
(OUTPUT
R) TP1
(GND)
(OUTPUT
L)
30