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. Adjusting procedure for the LED tight-up point is,
apply a -10dB
(0.3V) signal to the LINE INPUT _
jack,
unplug
the jumper
between
ACCESS
SEND
and RECEIVE
jacks and plug in an AC voltmeter
to the ACCESS
SEND jack. Set the AUX
B Module
INDICATOR
SELECT
switch to NORM
and adjust
the INPUT
Module TRIM
knob for a -30dB
{0.3V)
reading on the AC voltmeter.
Next, raise the LINE
INPUT
level to +15dB
(5.6V) and adjust R101
so
that the LED
tights-up.
The LED may remain lighted even though the tevel is
decreased
by 1 to 1.5dB from +15 dB, but this is due
to the hysteresis of the circuit and not a malfunction.
. When
the ACCESS
SEND
level is -10dB, the-slider
terminal
level of R101
will be -33dB
(22mV}, and
when
the ACCESS
SEND
level goes up by 25dB
beyond -10dB, this level will be -8dB (0.4V).
. The gain of U5-2 will vary in accordance to the ON
or OFF
state of G7. When
the BUSS MASTER
5.5 AUX 1 —» AUX A SEND
1.
Module INDICATOR
SELECT
is at NORM, ON will
be applied
to the
INPUT
Module
edge connector
J1-4, and +10V when the INDICATOR
SELECT is at
MIX. Q7 will be ON at MIX, and OFF at NORM
Thus, the gain of U5-2 will be, R26/R27+R27 = 8dB
at MIX;
and.
R26 + R28/R26 + R27 + R28 = 28dB
at NORM.
Consequently,
against
the -10dB
(0.3V)
ACCESS
SEND level, the output level of U5-7 pin #7 will be
-25dB
(0.056V)
at NORM;
and -5dB
(0.56V}
at
MIX.
The LED will light-up when the US-1 pin #2 level is
1V (0dB).
The potential of 0.7V at the junction of
R30 and R31 is rectified by diode D-6, the resulting
1V DC applied to U5-1
pin #2, compared with the
level at pin #3. When
this rectified DC potential is
above 1V, output pin #1 of US-1 will be ~15V; and
when
below
1V, will be +15V,
Q8 will switch ON
when the potential is -15V and the LED will light-up.
fal
RINE OUT (xe
Eg
AUK OUT
(22/10)
TAPE A IN (x0)
FLB
10)
TAPE 8 IN (x8)
Above, NOMINAL
Apply a -10dB
(0.3V) signal to the LINE INPUT
jack of the INPUT Module.
. Plug in an AC voltmeter to the AUX A SEND jack of
the AUX A Module, The AC voltmeter recommended
for this measurement should have an input impedance
of 50kohms
or more,
input capacitance
less than
20pF, and a sensitivity of -60dB.
. Set panel controls an the Model
301
Input Module
and Model 303A Aux A Module as follows:
INPUT Module
INPUT select switch:
LINE
TRIM
: About ~20 on scale
AUX 1
: At max. CCW or CW (PRE-
FADER at CCW, POST FAD-
ER. at CW)
FADER
: At "0" on scale
AUX A Moduie
AUX A MIX
AUX A MASTER
Max. CCW
At "0" on scale
. The circuit is in normal condition
if the AUX A
SEND output is -2.2dB (0.775V) against a ~-10dB
LINE
IN level
. If the output is not -2.2 dB, adjust the INPUT Module
TRIM knob. The circuit is in normal condition if the
TRIM
adjustment
is between
10 and
15dB
on the
scale.
. If the circuit
is not functioning
properly, compare
the levels with the block diagram and check the DC
voltages and signal
levels in the AUX
A Module cir-
cuit schematic.
. Check the AUX 1 signais from all remaining 23 chan-
neis of the INPUT
Module in the same way.
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