(4)
The computer power interrupt has the highest priority among the failure warnings and causes a shutdown of the computer. On initial startup or a loss of power for more than three seconds a COLD start signal commands the computer to acquire new data for its memory. The power supply has short circuit and overvoltage protection, which trips the dc power when dc voltage is 120% of normal.
(5)
During normal operations, if the 115 volt ac input drops below a preset level, the power interrupt logic commands the computer to temporarily store critical information. If power loss continues beyond 50 milliseconds a change in reset logic commands a halt to computer operation. If the power level rises above the preset value in 1 to 3 seconds after power interrupt a WARM start commands the computer to continue operating using the data that was temporarily stored in the random access memory (RAM).
K. Self Test Operation
(1) The computer is instructed to perform one of three self test programs which exercise most of the computer operations. Each test is selected by rotating the front panel TEST SELECT switch to the desired test and then pressing the PUSH TO TEST switch to enable the appropriate test program.
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(2) The FUNCTION test performs computation based on stored (simulated) values of static pressure, pitot pressure and temperature probe inputs. This test sends fixed values on all computer signal output lines. The receiving units may take up to one half minute to stabilize. The SLEW test sets altitude rate to 600 ft/min. The FAIL TEST verifies its integrity of the failure warning circuits and activates all failure warning outputs. When each test is successfully completed the TEST VALID WHEN LIT light comes on within two seconds after test is initiated and all unit readings are stabilized.
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NOT OK
OK
THERE IS AN ADC PROBLEM - Replace the left (right) ADC (AMM 34-12-11/401). The system is OK.
THERE IS NO AIR DATA SYSTEM PROBLEM - The system is OK.
Air Data System - Troubleshooting
Figure 101
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A
737-300/400/500MAINTENANCE MANUAL
AIR DATA SYSTEM - FAULT ISOLATION
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1. General_______
A. This subject has one task. The task is to isolate a fault in the air data system.
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AIR DATA SYSTEM - ADJUSTMENT/TEST
_________________________________
1. General_______
A. This procedure contains two tasks. The first task is the operational test of the Air Data Computer (ADC). The second task is the system test of the Air Data System (ADS).
B. This procedure will do a test of the ADC installation, the air data indicators, and the pneumatic system.
TASK 34-12-00-715-001
2. Air Data System - Operational Test__________________________________
A. General
(1) The ADS operational test is a BIT (built-in-test) test. The test operates from the controls on the front panel of the ADC. During the test, stable outputs are sent to the air data instruments and are monitored. The test makes sure of the conditions that follow:
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