www.SteamPoweredRadio.Com
V.
Electronic Assembly
The
electronic assembly consists of a record cha
nn
el, a reproduce chan-
nel, a bias and erase osci
ll
aror, and a power supply, mounted on a single
chassis.
The
record c
hann
el
consists
of
a rwo-srage mi
cropho
ne preamplifier
Vl0l
and
Vl02A
and
a three-stage amplifier,
Vl02B,
Vl03A,
Vl03B
(F
ig.
5.3).
Whe
n dummy
plug
J 107P is inserted
in
receptacle
JI
06S in the micro-
phone
pre
am
pl
ifi
er, the micr
opho
ne
input
marches a hi
gh
impedance
microphone. A plug-in transformer, available as accessory
equipment,
will
pr
ovi
de
the
proper
march for a low impedance microphone.
The
M I
CROPHONE
inp
ut J
I0IS
and LJNE
IN
P
UT
J 102S have sep-
arate controls
RI
06
and R 125 respectively. B
oth
inputs can be
use<l
simultaneously. Mix
ing
takes place in the first srage
of
the record
am-
plifier,
VI
028.
Signals in the record channel are picked off the
RE
C-
ORD
CALIBRATION
potentiometer R 114 at the
output
of this srage,
a
nd
can be switched
to
the
output
amplifier thr
ough
the
MONITOR
SELECTOR sw
it
ch
S102, for monitoring.
Record equali
za
tion, accomplished in the
grid
circuit
of
VI
03A,
and
the ca
th
ode
circuit of V I 03B,
is
adjusted by
trimmer
C I 07. Plate volt-
age is supplied to
the
last stage ot the record amplifier,
Vl038
011/y
when
switch S20 l on
th
e rape tran
sport
is
m the REC position.
The
r
ep
roduce channel consists
of
a
LWO-stage
reproduce
ampl
i
fie
r,
Vl04,
Vl05
and a
cw
o-stage
output
amplifier
Vl06A
and
Vl068.
The
signal from the reproduce head appears
at
connector
Pl
0 IP.
Re-
produce equalization
is
provided by
Cl
16
and
R 130. Level
is
adjusted
by potentiomecer
Rl
37.
The
re
prod
uce signal is f
ed
to
che
output
amplifier through che
MONI-
TOR
SELEC
TOR
switch when it is
in
tape position.
The
output
ampl
i-
fier consists
of
one voltage
amp
lification srage V 106A, and a cathode
follower output stage V 106B, which is transformer-coupled ro
OUT-
PUT
connector J 104S. A v-u meter and resistor shunt chis connector.
The
bias and erase oscillaror
is
an
LC
push-pull osci
ll
aror
operating
at
approxima
tely 100 kc.
The
NO
ISE
BALANCE
potenciometer R 147
co
mm
on
co
both
gr
i
ds
of
the
osci
ll
ator
is
adjusce<l
to
elimin
ate
any
asymmetry
in
wave form. Lack of wave symmetry would introduce a
d-c
current
in
the record head, causing
pe
rm
anent
magn
et
ization and a
resultant discorred signal. Bias level is adjusted
by
trimmer
Cl
13.
The
oscillacor, dependent
on
place voltage, operates only when switch
S20
1
is in
the
REC
position.
GENERAL
RECORD
CHANNEL
REPRODUCE
CHANN
E
BIAS
AND
ERASE
OSCILLATOR
5-1
To Next Page
Loading...