(d)  
The continuous data program pins are jumpered to assure non-interrupted altitude data, regardless of validity, to the flight control computer (FCC).

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 ú ú 01 Page 11 ú Mar 15/92

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 D. Self-Test
 (1)  A PRESS TO MONITOR switch and fault/status lights are provided on the front panel of the LRRA receiver/transmitters. Refer to 34-48-03/101, Troubleshooting for use of the switch and lights.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH EFIS ú

 34-48-03

 ú ú 01 Page 12 ú Jul 15/92
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 LOW RANGE RADIO ALTIMETER SYSTEM - TROUBLE SHOOTING
___________________________________________________
 1.  General_______
 A.  Replace defective components with known good components.
 B.  Do the troubleshooting and replace components in the sequential order shown in the Troubleshooting Procedure.
 C.  When you complete the troubleshooting, do the Low Range Radio Altimeter System Operational Tests (AMM 34-48-03/501).
 D.  The captain's radio altimeter system (LRRA-1) and EFIS interface components are: radio altimeter receiver/transmitter No. 1, transmit and receive antennas No. 1, EFIS control panel No. 1, symbol generator No. 1, and EADI No. 1.
 E.  The first officer's radio altimeter system (LRRA-2) and EFIS interface components are: radio altimeter receiver/transmitter No. 2, transmit and receive antennas No. 2, EFIS control panel No. 2, symbol generator No. 2, and EADI No. 2.
 2.  Troubleshooting Procedure__________________________
 A.  Prepare To Troubleshoot
 (1)  
Supply electrical power (AMM 24-22-00/201)

 (2)  
Make sure the EFIS system is serviceable (AMM 34-22-00/501).

 (3)  
Make sure these low range radio altimeter (LRRA) system circuit breakers are closed:

 (a)  
P18 Load Control Center - Left
 1) RADIO ALTM-1

 (b)  
P6 Load Control Center - Right
 1) RADIO ALTM-2

 (4)  
Set the EFIS transfer switch on the P5 overhead panel to the NORMAL position.

 (5)  
Look for the letters RA (in a yellow box) at the RH corner of an operational EFIS system EADI.

 (a)  
No letters RA in a yellow box and no radio altitude value indicates a possible EFIS system fault or a disconnected antenna. Go to the LRRA/Interface System Troubleshooting.

 (b)  
The letters RA in a yellow box indicate a LRRA system fault. Go to the LRRA R/T and Antenna Troubleshooting.

 B.  LRRA R/T and Antenna Troubleshooting
 (1)  
Set the EFIS transfer switch to the NORMAL position.

 (2)  
Push and hold the PRESS TO MONITOR pushbutton on the front face of the applicable R/T.

 (a)  
If the XMTR light comes on, or any of the other lights on the R/T come on, replace the applicable R/T (AMM 34-48-21/401).

 (b)  
If the SENS, WARN, and FLAG lights come on, inspect the connector pins on the rear of the R/T and the mating connector on the rack for bent pins and damage. Repair or replace, as required.

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 (c)  
If the SENS, Warn, and FLAG lights still come on, replace the applicable receive or transmit antenna (AMM 34-48-11/401) or repair/replace the coaxial cables connected to the antennas, as required.
　
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