TM 11-6625-2735-14-1
+110-Volt Supply. CR1412 functions as a full-wave
center-tapped rectifier and provides an unregulated out-
put voltage (approximately +136 volts) for the +110-Volt
Power Supply. This voltage is filtered by C1412 and is
connected to the +110-Volt Series Regulator, Q1496, to
provide sufficient collector supply for stable regulation
over a wide range of ac power line voltages. Transistors
Q1490 and Q1494 are connected as a comparator. A
sample of the output voltage from the +110-Volt Supply,
through divider R1486, R1487, is connected to the base of
Q1490. The base of Q1494 is connected to the +50-Volt
Supply to provide a reference voltage. The error output at
the collector of Q1494 reflects the difference, if any,
between these 2 inputs. This error output drives Q1496
and controls the output voltage of the power supply.
Regulation occurs as follows: If the output level of this
supply decreases (due to an increase in load, for example)
the voltage at the base of Q1490 decreases also. This
decreased voltage when compared to the reference
voltage at the base of Q1494 results in a decreased voltage
at the collector of Q1494. A portion of this decreased
voltage is connected to the base of Q1496 causing
increased conduction. The output voltage increases,
thereby achieving regulation of the +110-volt power
supply.
A current limiting stage, Q1497, protects the +110-Volt
Supply if excess current is demanded from this supply. All
output current from the +110-Volt Supply must flow
through R1489. Transistor Q1497 senses the voltage drop
across R1489. Under normal operating conditions, Q1497
is biased off. However, when excess current is demanded
from the +110-Volt Series Regulator due to a short circuit
or similar malfunction at the output of this supply, the
voltage drop across R1489 increases until it is sufficient to
forward bias Q1497, The collector current of Q1497 pulls
the base of Series Regulator Q1496 positive and turns it
off. The output current from the supply is then limited by
R1488 and the +110-Volt Supply is thereby protected.
+5-Volt Supply. Basic operation of all stages in the +5-
Volt Supply is the same as described in the +50-Volt
Supply and the +15-Volt Supply. The +5 volt reference for
this supply is established by divider R1454-R1455 between
+50 volts and ground. Any change in the output level of
the supply is compared at Feedback Amplifier U1454B
which produces a signal of inverted polarity at its output
(pin 7). This change is coupled to +5-Volt Series
Regulator Q1456 to correct the change in the output
voltage. Transistor Q1454 provides current limiting (fold-
back operation) if the supply load increases beyond preset
limits or becomes shorted to ground.
–8-Volt Supply. Basic operation of all stages in the –8-
Volt Supply is the same as described in previous supplies.
The reference level for this supply (0 volt) is established by
the ground connection through R1463 to pin 2 of Feed-
back Amplifier U1464A. Feedback voltage to pin 3 of
U1464A is provided by divider R1464-R1465 between +50
volts and the –8-Volt Supply output. The divider ratio of
R1464-R1465 is 10:1 so the level at pin 3 is 0 volt when the
supply is operating properly. Any change in the output
level of the supply is compared at U1464A, which
produces a correction signal of the same polarity as its
output (pin 1). This change is coupled to the –8-volt Series
Regulator, Q1468, through Q1466 to correct the change in
output voltage. Transistor Q1464 provides current limiting
(foldback operation) if the supply load increases beyond
preset limits or becomes shorted to ground.
–15-Volt Supply. Basic operation of all stages in the
–15-Volt Supply is the same as described in the –8-Volt
Supply. The reference level for this supply (0 volt) is
established by the ground connection through R1473 to
pin 6 of Feedback Amplifier U1464B. The feedback voltage
(0 volt) to pin 5 of U1464B is provided by divider R1474-
R1475 between +50 volts and the –15-Volt Supply output.
Any change in the output voltage of the supply is
compared at U1464B, which produces a correction signal
of the same polarity at its output (pin 7). This change is
coupled to the base of –15-Volt Series Regulator Q1478 to
correct the change in output voltage. Transistor Q1474
provides current limiting (foldback operation) if the
supply load increases beyond preset limits or becomes
shorted to ground.
+15-Volt Supply. Basic operation of all stages in the
+15-Volt Supply is the same as for the +50-VoIt Supply.
The +15 volt reference for this supply is established by
divider R1444-R1445 between +50 volts and ground. Any
CRT CIRCUIT
change in the output level of the supply is compared at
Feedback Amplifier U1454A, which produces a signal of
General
inverted polarity at its output (pin 1). This change is
coupled to +15-Volt Series Regulator Q1448 through
The CRT Circuit provides the voltage levels and control
Q1446 to correct the change in output voltage. Transistor
circuits necessary for operation of the cathode-ray tube
Q1444 provides current Iimiting (foldback operation) if the
(CRT). Fig. 3-10 shows a detailed block diagram of the
supply load Increases beyond preset limits or becomes
CRT Circuit. A schematic of this circuit is shown on
shorted to ground.
Diagram 12 at the rear of this manual.
3-24
To Next Page
Loading...
Need help?
General
