TM 11-5835-241-13&P
amplifier and to improve frequency response.
Degenerative feedback
is also provided in the emitter circuits to stabilize the dc operating
point of the amplifiers.
Recording levels are adjusted using RECORD
Record calibrate control R10 adjusts the drive to
LEVEL control R3A.
the record head so that the desired degree of magnetization is produced
It is adjusted so that audio
for a given reading on the VU meter.
peaks reading 0 to +2 on the VU meter just produces magnetic saturation
R14, C7, R15, and C10 form an equalization network to
of the tape.
compensate for response characteristics of the record head so that
R15 and C10 provide low frequency (below
"flat" response is obtained.
200 Hz) boost while R14 and C7 provide high frequency (above 1500 Hz)
In the PLAY position of S6, B+ is applied to the emitter cir-
boost.
In the RECORD position, S6 closes the B+
cuit of Q2 to bias it off.
line, disabling the amplifier.
Record driver Q4 amplifies the signal to drive record head
d.
PU1.
C13, C14, and L2 form a series resonant high frequency boost
Noise above 20 kHz is also suppressed.
circuit up to about 20 kHz.
At tape speeds of 7.5 inches per second, C13 and L2 are used. At tape
speeds of 3.75 inches per second, C14 is connected in parallel with
This increases high
C13 by contacts of speed selector switch S9.
frequency respsonse of the recording head at the lower tape speed.
L1 and C12 in the collector circuit is a parallel resonant bias trap
This
to isolate the high frequency record bias from amplifier Q4.
reduces loading on the bias oscillator.
BIAS OSCILLATOR.
Refer to block diagram, figure 4-1 and schematic diagram,
a.
Bias oscillator Q13, Q14 produces a supersonic current
This bias current is used in the
at a frequency of about 80 kHz.
erase head to erase the tape before recording and in the record head
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