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In addition to transferring the record amplifier output from ground to the
bias amplifier board, relay KI01 also causes indicator lamp DSI03 to light through
contacts 1Z and 8 and applies +Z8 volts to energize the bias and erase amplifiers at
terminal lZ on the Bias and Erase board
(1).
Inductive surge from the coil of KI01
is l;>uppressed by diode CRI0l.
NAB Reproduction
Signals recorded by the NAB record circuits described above are re
produced from the corresponding playback head and applied to the NAB pre
amplifier board in slot 7.
The preamplifier board contains high-frequency and
low-frequency amplitude equalizers for two tape speeds.
The proper equalizers are
selected by a relay on the board, which is energized by a voltage introduced through
terminal ZO.
High-frequency and low-frequency equalizer networks are provided
for each tape speed.
Phase correction networks are selected by another relay with
a separate network for each speed.
This relay is energized by a voltage introduced
through terminal 19.
The phase correction networks are not adjustable.
At the pilot connector JIll all signals may be fed out on terminal Z with
return on 5, in order that the pilot,
if
any, may be extracted free from gain varia
tions occasioned by adjustment of the GAIN CAL. potentiometer which feeds the
main audio signal out on terminal ZZ.
When the REC. SELECT switch is in the RDY position, the record hea.d is
connected to the output of the bias and erase board; +Z8 volts is supplied from the
power and meter assembly in slot 5 through terminal lZ to this switch, to terminal
13 of the record relay so that it may be operated by grounding its terminal 14 through
diode CRIOZ; and to terminal 10 of JlI0 at the tape transport.
The signal from terminal 16 of slot 8 is routed through the REC. SELECT
switc h to the REPRO. LEV EL control and an a ttenua tor comprising
R
104 and
R
105.
With the METER switch in the CAL. position, the signal from the attenuator is
routed to the line amplifier circuit card in slot 6, where it is amplified and applied
to the outgoing line.
A selector switch at the output of the line amplifier normally
connects the output through terminal Zl to transformer TZ, which is provided with
impedance ma tc hing resistor sRI 08 and R 109
.
The output impedance may be set by
means of switch 5106 to 150 or 600 ohms.
Switch 5105 is a three position switch
providing ISO-ohm, or 600-ohm termination of the outgoing line when it is not ter
minated externally. The outgoing line connects to connector JIOZ. When the selector
switch at the amplifier output is set to route the signal to terminal ZO, an 8-ohm
loudspeaker may be driven directly from terminal 3 of PILOT connector JIll
.
Speaker return is to terminal 6.
Earphone monitoring is provided by jack JI03.
This jack is "floating" and headphone leads should not be grounded.
The output
signal from TZ is applied through terminals Z and 4 of the line amplifier board to
an attenuator which supplies the attenuated signal for the VU meter through terminals
M64 PAR Z-71
87
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