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3.
Reset LINE INPUT level control to obtain a VIVM reading of exactly
-20 db (77.5 mV).
NOTE:
If bias
frequency
signal
leakage
is indicated
on the VIVM,
a filter
as shown in Fig. 12 can be used at the input of
the VIVM.
Record signals from 50 cps to 15 ke at 7-1/2 ips, or from 50 cps
to 7.5 ke at 3-3/4 ips on tape, and read the output on VIVM.
Check
the
frequency
response
of both
channels.
If adjustment
is required,
replace
C65 for 7-1/2 ips and C64 for
3-3/4 ips.
Record
Noise
Check
Ls
2.
3.
4.
While recording a 500 cycle signal on the tape, adjust LINE INPUT
level
control
to obtain
a VIVM reading
6 db above
normal
operating
level.
Set the LINE and MIC INPUT level controls
to minimum.
Rewind the tape to the beginning portion of the
500 cycle recording.
Record the tape with LINE and MIC INPUT level controls
at minimum
position,
over the portion where plus 6 VU recording was made, and
make
certain
that
erasure
is being accomplished.
Erase
the tape by recording with no signal
input.
Rewind
the tape to the beginning
of the recording.
Read the VIVM indication for noise level while playing back the
portion which had been previously recorded.
Record
Amplifier
Check
If a check
of the record
amplifier
is required,
connect
a signal
gene-
rator
to record
input circuit
as
shown
in Fig.
12, then check
the
frequency
response,
noise,
amplifier
gain,
etc.
NOTE:
To avoid
overloading
the amplifier,
frequency
response
check
should be made at least 20 db below normal
operating level.
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27 -
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