S.3.1
VOLTAGE REGULATORS
The
power supply voltage regulators are shown on Schematic No. 102810, sheet
2.
J212
(zone
F16)
connects unregulated +20v,
-20v,
+10v, and auxiliary
21v
ac
for
the brush
motor driver and ac motor control circuit to the
Servo PCBA. Note that
two
pins are
allocated to the high current lines to reduce the current density in the pins.
The
+10v and
-10v
regulators
are
series regulators using zener diodes
VR4
and
VR10,
respectively, for the voltage reference.
The
emitter base junction
of
028 is in series with
VR4,
and diode
CR43
is in series with
VR10,
thus improving the temperature stability
of
the supplies.
The +
Sv
and
-Sv
regulators consist
of
two
similar circuits whose outputs
are
set by
potentiometers
R1S8
(zone
F14)
and
R167
(zone
E14).
Outputs
of
the +
Sv
and
-Sv
regulators
can
be monitored at
TP4
and TP12, respectively. Operational amplifiers
U1S
and
U18
are used as voltage followers in the regulating circuit. The high open-loop gain of the
operational amplifier in the feedback regulating circuit offers improved
line and load
regulation characteristics
to
the +
Sv
and
-Sv
supplies. Zener diodes
VR7
and
VR11
provide the
volt~ge
references for +
Sv
and
-Sv.
Diodes
CR38,
CR40,
and CR42,
CR44
improve the temperature stability of the supplies.
Regulator power transistors
Q24,
02S, 026,
033
are mounted on heatsinks external to the
Servo PCBA. J204 and
J208
connect the regulators to the external heatsink.
A
crowbar over-voltage protection circuit
is
provided for the +
5v
and
-Sv
suppl ies. These
circuits
are
employed to detect
an
increase
of
3v
in the +
5v
supplies. Zener diodes
VR8
(zone
F11)
and
VR9
(zone
E12)
detect
an
increase in the +
5v
and
-Sv
suppl ies,
respectively. An increase to
+8v
or
-8v
causes
SCR3
or
SCR4 to fire, which in turn
causes the +
20v
or
-20v
fuse on the power supply module to blow, thus removing the
relevant
20v
supply.
A
crowbar over-voltage protection circuit is also provided
on
+ 10v and
-10v
supplies and
employ zener diodes
VRS
and
VR6
(zone
F1S),
VR12
and
VR13
(zone 014), respectively,
to
detect
an
increase in the +10v supplies. A voltage increase to +15v or
-1Sv
causes
SCR2
to blow, thus removing the relevant
20v
supply.
J209 (zone G,H-10) and
J211
(zone D,E-10) are jumper plugs which connect unregulated
+
20v
and
regulated
+Svand
+ 10v from regulators to the remainder of the circuits
on
the
Servo PCBA and to the Logic PCBA via J210. These jumper plugs enable the isolation of
the regulators and power supply for maintenance purposes.
The unregulated +
20v
supplies
are
used
in
the positioner power amplifier and the power
clear circuit.
In
addition, the
-20v
supply is used in cartridge lock solenoid driver and
emergency unload relay driver. The +
Sv
regulators supply power to the digital ICs, linear
ICs, mode control electronics, brush motor driver,
ac
motor control circuit, relay driver,
and cartridge
lock solenoid driver. The
+10v
regulators supply power to the operational
amplifiers, velocity function generator, mode control electronics, position transducer
signal conditioners, and position transducer lamp driver.
5.3.2
POSITIONER
SERVO
ELECTRONICS
The positioner electronics consists of the Velocity Function Generator, Mode Control
circuits, Position Transducer Signal Conditioners, Velocity Transducer Amplifier,
Summing Amplifier, Positioner Power Amplifier, Position Transducer Lamp Driver Failure
Detector, and the Emergency Unload
System. Refer to Paragraph
S.2
for definition
of
logic
tetm mnemonics used
in
the following descriptions.
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