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5.
LEVEL
SETTING
AND
OPERATION
CHECK
5.1
LINE
IN —
ACCESS
SEND
1. Apply a -10 dB (0.3V)
signal to the LINE
INPUT
jack on back panel of the Mode! 301 Input Module.
2. Pull
out
the jumper
between
ACCESS
SEND
and
RECEIVE
jacks for the channel in which the above
signal is injected, and plug in an AC voltmeter to the
ACCESS
SEND
jack.
The
AC
voltmeter
recom-
mended
here should have an input impedance of 50k
ohms or more, input capacitance less than 20 pF, and
maximum
sensitivity
of -60 dB
with
a sensitivity
selector switch.
3. Set controls on panel of the Modei 301 Input Module
as follows:
INPUT select switch:
LINE
TRIM
: At about -20
4. For a normal condition of the circuit, the ACCESS
SEND
output
should
be -10 dB against a LINE
IN
signal of -10 dB.
5. If the output is not -10 dB, adjust with TRIM. After
this adjustment,
the TRIM
knob should be between
10 and 18 dB under normal condition.
6. !f you notice any malfunction,
refer to the pream-
plifier (Q1 ~
Q6)
circuit
schematic
and check
all
transistor voltages and signal levels.
7. Check all remaining Input Modules in the same way.
8. 'Measurement of frequency response,
S/N ratio,T.H.D.;
Frequency response:
20H2z ~ 20 kHz, within £1dB
S/N ratio
More than 84 dB
(using a weighting network}
80dB
(measured with a band-
pass filter — 20Hz ~ 20 kHz
A more than 78 dB reading on
an AC voltmeter with a better
than
100kHz
range
can
be
said as normal.
Less than 0.03 %
{at 20 Hz ~ 20kH2)
or, :
or, +:
T.H.D.
5.3
LINE IN
LINE OUT/AUX OUT
InpuT MODULE
Ne
mic IN
1. Apply 2 -10dB (0.3V) signal to the LINE IN jack.
2. Plug in an AC voltmeter to the LINE OUT 1 jack on
rear of the Model 303A AUX A Module.
5.2
LINE
IN —+ DIRECT
OUT
ono
1g
ovpecT out
A asaner oes a0 MoM
1. Apply a -10dB (0.3V} signal to the LINE INPUT Jack.
2. Plug in an AC voltmeter to the DIRECT OUT jack
for the channel-in which the above signal is injected.
3. Set controls on
panel
of the
INPUT
MODULE
as
follows:
INPUT select switch:
LINE
TRIM
: To about ~20
EQUALIZER
Set to center the 3kHz and
200 H/800 Hz switches. Under
this condition,
response
will
be flat regardless to setting of
the 10k Hz and .75Hz control
knobs,
INPUT FADER — : "O" scale
4, The circuit isin normal condition if the DIRECT OUT
level is -10 dB against the LINE IN level of -10 aB.
5. If it is slightly off -10dB, adjust by the TRIM knob.
For a normal condition circuit, the TRIM knob posi-
tion should be between 10 and 15 dB.
6. If you cannot
obtain the proper reading, check the
circuit,
If the above Item 5.1 check shows normal but the
DIRECT OUT level is incorrect, trouble could be in
the INPUT FADER, and IC's U1 and U4, The gain of
U1-7 and U4-7 is 1, and that of U4-1 is 10dB.
The attenuation of the INPUT FADER set at infinity
should be:
More than 85dB at 30 Hz
More than 75dB at.
1k Hz
More than 58 dB at 10 k Hz
® LINE OUT (0)
@' sux OUT
3. Set the level selector switch (S1~ S4) on the PCB of
the AUX
A Moduie
to-LO.
This selector switch
is
located as shown
in Page 10.
7
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