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BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
Built-In Test Equipment
The BPCU BITE helps you isolate faults with the external power
circuit. The BPCU BITE operates independently of the normal
control and protective circuits. The BPCU has these BITE
functions:
* Detects and identifies failures in the external power channel
* Saves fault information in its non-volatile memory
* Shows fault information on the front of the BPCU (indicator
lights)
* Does a self test of the BPCU circuits at power-up and when
you push the TEST switch on the front of the BPCU.
The BPCU BITE has these three operating modes:
* Continuous monitoring
* Protective faults
* Self-test.
BITE Front Panel Display
The BITE front panel display has a TEST switch and four lights.
You use the test switch to turn off any fault lights and to do a test
of the BPCU. The BPCU FAULT and BPCU PASS lights are the
only lights that come on at the end of the self test.
During continuous monitoring and protective fault modes, only
one fault light comes on at a time. There is a priority if the BPCU
see two faults at the same time. This is the priority for the lights:
* BPCU FAULT
* EP DIST/BUS FAULT
* EPC FAULT
* BPCU PASS (green).
Monitor FAULT
Monitor BITE compares cause and effect relationships to find
out if there is a fault condition. After a protective action occurs,
the monitor BITE isolates the fault. The monitor BITE is
continuous when the BPCU has power. Monitor BITE isolates
faults to one of these:
* BPCU FAULT
* EP DIST/BUS FAULT
* EPC FAULT.
Protective Fault BITE
Protective fault BITE occurs when a fault condition makes the
ground service relays or the EPC open.
Protective fault BITE isolates faults to these:
* External power
* The tie bus
* The transfer buses.
You must do a self-test BITE after fault isolation to make sure
the fault is gone. The BPCU shows the fault by an EP DIST/BUS
FAULT (red) light.
EXTERNAL POWER - BPCU - TRAINING INFORMATION POINT
EFFECTIVITY
GUN ALL 24-40-00
Page 27
D633A101-GUN Jun 10/2005
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
24-40-00-095
Self-Test BITE
Self-test BITE looks for BPCU passive circuit malfunctions. Selftest
BITE isolates faults to the BPCU and shows this by a BPCU
FAULT (red) light.
You push the BPCU TEST switch to do a manual self test. When
the test occurs, all lights come on for 3 seconds. Then all the
lights go off. If there are no BPCU faults, the green BPCU PASS
light comes on for 7 seconds. The red BPCU FAULT light comes
on if it finds and internal fault. Any previous fault lights that were
on go off at the start of this test and do not come on until the
BPCU finds the fault again.
Self-test BITE is automatic when the BPCU receives power and
the airplane is on the ground. No lights come on if the test
passes. If the BPCU finds faults, the red BPCU FAULT light
comes on, and previously latched faults are reset.
EPC FAULT
The BPCU EPC fault (red) light monitors the voltage of the EPC
close signal and the position status of the EPC. The EPC fault
light comes on if the position does not match the commanded
position.
BPCU DIST/BUS FAULT
The BPCU monitors internal protective functions. The EP DIST/
BUS FAULT light comes on when the BPCU opens the EPC,
BTB1, BTB2 for any of these faults:
* Overcurrent
* Unbalanced phase current.
BPCU FAULT
The BPCU FAULT light comes on if the BPCU fails a self test
BITE or the BPCU goes into fail-safe protection.
BPCU PASS
The BPCU PASS light (green) comes on when you push the
TEST switch and the BPCU is good.
BPCU Test Switch
You push the BPCU test switch to make the BPCU do a self test.
The test turns off any fault light that is on before the test. The
fault light will come back on when the conditions that made the
light come on are true again. Not like the GCU, the BPCU
responds to the test switch if it’s associated AC power source
(external power) is on the airplane.
EXTERNAL POWER - BPCU - TRAINING INFORMATION POINT
EFFECTIVITY
GUN ALL 24-40-00
Page 28
D633A101-GUN Jun 10/2005
BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
24-40-00-095
EXTERNAL POWER - BPCU - TRAINING INFORMATION POINT
EXTERNAL POWER - BPCU - TRAINING INFORMATION POINT
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