TM 55-4920-428-13
1-22. BITE Circuit (FO-2).
a. When SYSTEM SELECT switch S3 is at BITE, the following circuits are completed.
(1) The DVM is connected to BITE switch S5A moving contact 11A, At each BITE switch position, a volt-
age is displayed on the DVM.
(2) A simulated transducer signal is connected to BITE switch S5B moving contact llB. The simulated
transducer signal is applied through the BITE switch to the selected demodulator circuit.
(3) Load resistors R59 and R69 are connected to the SAS 1 and SAS 2 servo output amplifiers, respec-
tively. The load resistors substitute for the extensible link servo valves,
(4) BITE switch S5C contacts llC and 6 have +28 volts dc available for K1 operation on TB6B.
b. The five dc power supply voltages are applied to voltage divider networks. When the BITE switch is at
–20V, +20V, – 12V, + 12V, or +5V, the voltage from the associated network is displayed on the DVM.
c. The 13 volts ac 400 Hz reference is applied to voltage divider R71 and R70, S3 B3, and S5B. When the
BITE switch is at SAS 1 SELF, SAS 1 CROSS, SAS 2 SELF, or SAS 2 CROSS, the signal is applied to the corre-
sponding demodulator. The demodulator processes the signal and produces a self or cross output signal. The out-
put signal is applied through S5A contacts of the BITE switch and fed to S3 A1. From pin 4 it goes through the
precision rectifier and auto range circuit to DVM D1.
1-23. HYDRAULIC UNIT 145GS278-2.
1-24. Circuit Description (FO-3). The hydraulic unit provides high-pressure and low-pressure hydraulic fluid
from a test stand at two controllable supply pressures up to 2500 psig (high-pressure side) and 300 psig (low-
pressure side) to the ILCA under test. The return line operates at 60 psig controlled by preset check valves be-
tween RETURN selector valves VR1 and VR2 that connect the return flow from the ILCA to the RETURN
port. Pressure reducing valve VR6 allows bypass flow from LOW PRESS REGULATOR VR7 at pressure levels
above the 300 psi set point. HIGH PRESS RELIEF VALVE VP6 and LOW PRESS RELIEF VALVE VR8 re-
lieve trapped pressure from the high and low pressure circuits to return at shutdown.
Fluid from the test stand enters the hydraulic unit through SOLENOID valve VP5 and the 5-micron filter, At this
point, the flow is divided: one branch flows into a high-pressure circuit; the other branch flows through flow lim-
iter valve VR9 to a low-pressure circuit.
In the high-pressure circuit, the flow is through HIGH PRESS REGULATOR valve VP4 to HIGH PRESS gauge
G1. Variable area HIGH PRESS SHUTOFF VALVE VP3 controls flow to the four selector valves: ILCA PRESS
SYS-1 VPl, ILCA PRESS SYS-2 VP2, SAS PRESS SYS-1 VS1, SAS PRESS SYS-2 VS2 and these control flow
to the ILCA manifold, With HIGH PRESS SHUTOFF VALVE VP3 set to PRESS, regulated pressure flows to
the four selector valves, which permits flow to the ILCA manifold. At VENT, these valves connect the pressure
ports of the manifold to return through the low pressure check valve that is preset to 3 to 5 psig. Normally closed
HIGH PRESS RELIEF VALVE VP6 relieves pressure from the regulated supply to return at shutdown.
Change 3
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