TM 11-5820-801-30
The low side of the + 12 V output and the high side of
secondary windings, one for each voltage regulator, and
the 12 V output are tied together to provide a common +
12 V return line
six singlephase secondary windings that supply the
b. Rectifier Board A 7 (fig. 2-19). Rectifier Board A7
internal bias voltage (when rectified in the individual
circuits) to the five gate circuits (A2, A3, A4, A5, A6) and
contains four three-phase full-wave bridge rectifiers. The
to the 1000 V regulator A9.
+ 12 V and 12 V rectifiers have an RC filter in the output
(3) Capacitor C1 is across the high voltage
circuit. These two bridge rectifiers are identical and
output of the rectifier board and capacitor C2 is across
supply the 12-V preregulators. They employ 1N4245
the high voltage (-1000 V) output of PSI A small (10-
diodes. The -1000 V bridge rectifier utilizes 1N3647
ohm) resistor is in series with C2. Circuit ground of the
diodes and the +6.3 V bridge rectifier, IN5550 diodes
c. +6.3 V Regulator A1 (fig. 2-20). The input voltage to
high voltage supply is separated from chassis ground by
RI (220 ohms). This is a safety device to ensure that the
power transistor Q1 is unregulated 12 V at terminals E2
chassis never rises more than 30 V above ground,
and E4. The output voltage of Q1 is 6.3 V at terminals E1
regardless of internal circuit failures such as ground short
of a high voltage circuit (1000 V regulator or 6.3 V
and U1, an integrated circuit voltage regulator, drives Q2
regulator).
and Q3. Resistor R4 produces a voltage drop
(4) Because the drift, ripple, and regulation of
proportional to output current. When this drop reaches
the 12-V regulators (A10, A 1) are very stringent,
about 0.6 V the drive current to Q2 and Q3 is depleted.
preregulators are employed between the regulators (A10,
Variable resistor R6 (a trimpot) permits adjustment of the
A 11) and rectifier board A7. These preregulators utilize a
output voltage to 6.3 V. If the output is shorted the
filter capacitor (C3, C4), a 7Zener diode (CR2, CR3), and
regulator will produce about 2.5 amps which will, in time,
a power transistor emitter follower (Q1, Q2) to provide
cause Q1 to overheat and fail Short duration shorts,
low ripple input to the 12-V regulators The 12-V
however, will not cause failure. To prevent cold turn-on
regulators are identical and, because they are potted in
surges from causing damage the input line (E2) has a 2-
epoxy, they are nonreparable They are capable of
amp fuse (F1) and the circuit is bridged by Zener diode
producing several times the power required in this
system. The regulated voltage is constant within + 0. I V.
2-25