Cw Timer - Swann CUBIC ASTRO 102 BX Service Manual

R LINE:
CRIOI
0111
CW LINE:
+fO.IIV
CW TIMER
RI20
"R" LINE CONTROL
CW OE:LAY
+lQ.llV
A~1I0AltD
KE:Y I
+IO.llV
,.
RIZI
1_'"
(
CIO.
I
~
I UIOI
RIZ. RI30
CRIIO
RI52
CRIII
011'
CW TIMER
allowed to conduct, charging
This lowers the base volt-
and bringing the "R" line to
RilT
PA BIAS
a
CWX L1NE
. CONTROL
CRIOT
R
OJvv\rt-l.
T
OJ'V\i'\r--.....
SSII
_CUBIC
COMMUNICATIDNS
S""AN
DIVIBIDN
Also, when the key line is high, CRI04 is
CI02 and biasing Ql06 on through Rl12 and Rl14.
age of QlO?, causing it to cease to conduct,
ground potential. When the key line
goes low, CI02 discharges through R-
112 and the RIIJ-Rl14 and Ql06 base-
emitter junction parallel combinat-
ion, delaying the turn off of QI06
and thus the return of the "R" line
to a high value. This is to assure
that there is a delay between the
deenergizing of the "T" line and the
reenergizing of the "R" line, so
that certain switching functions can
be accomplished without affecting
either receive or transmit function.
When semi-breakin is selected
the CW timer holds the base of Ql06
high for a brief time, preventing
return to the receive condition be-
tween characters. When full breakin
is selected, this feature is disabled.
When either the "T" line or the key line is high, voltage is applied to
QlIO, making it conduct. This brings the PA BIAS control line low, and turns
on the bias to the power amplifier stages. Also, the base of Qlll goes low,
allowing it to conduct. Qlll then conducts from the CW line through CRI09,
to the CWX line, energizing it.
Should, however, the "R" line be
high, voltage is applied through RIl?
to the base of Ql09, causing it to
saturate, and grounding the base of
QlIO, thus nullifying the effect of
the "T" and key lines outlined above.
Thus, there can be no output from the
transmitter until the antenna switch-
ing circuitry has returned to the
receive condition. This is an "in-
terlock" function, which prevents
damage to the receiver front end in
the event of a control malfunction.
CW TIMER
When the BREAKIN switch is in
the SEMI position, energization of
the "T" line applies a voltage to
the base of QIIJ, causing it to
saturate and the voltage at the
input of timer UIOl to go low. So
long as this condition pertains,
capacitor CIOS is prevented from
charging through R12S and the CW
DELAY control
by
diode CRIIO. When
the input is low, or until CIOS is
6-S