INTRODUCTION 



The reliability of operational shipboard electronic equipment has not im- 

 proved appreciably over the past few yecirs. Failure rates of electronic equipment 

 are still high and means to lower them should be ascertained. In many instances, 

 equipment which has been subjected to environmental testing in the laboratory 

 fails once it is installed and operating in its actual shipboard environment. Indi- 

 cations are that the present test methods have inherent deficiencies in that they 

 do not produce these potential failure modes and effectively simulate field fail- 

 ures during laboratory testing. Scrutiny of the test method for subjecting elec- 

 tronic equipment to environments in a sequential manner reveals two obvious 

 discrepancies: (1) the test method does not simulate the actual environmental 

 conditions in which the equipment is to operate, and (2) it does not subject the 

 equipment to the synergistic (interacting) effects of the true environments. 



If the reliability of shipboard electronic equipment is to improve in the 

 future, then, the potential failure modes and problem areas must be detected prior 

 to mass production of the equipment. This may be accomplished through simulat- 

 ing the total effects of the actual shipboard environment. In other words, the 

 equipment should be exposed to the synergistic effects as well as to the main ef- 

 fects in an environmental test. These combined effects have a detrimental effect 

 on the performance and failure rate of shipboard electronic equipment, as prior 

 tests have revealed. * 



The purpose of this report is to show the occurrence of the synergistic 

 effects in combined environments and their contribution to the degradation in per- 

 formance of shipboard electronic equipment. 



Subsequent sections will describe the test procedures and the verification 

 of synergistic effects in combined environments. 



The test facilities and instrumentation are described in the appendix. 



THE TEST PROGRAM 

 Test Specimen 



The intermediate-frequency, amplitude-modulation (if/am) amplifier 

 module was chosen for this particular test because of availability and suscepti- 

 bility to the environments as demonstrated in a previous combined-environment 

 test. The active components in the module are all solid-state devices. The 

 module receives a D00(±3)-kHz intermediate-frequency signal, demodulates and 

 amplifies the audio signal superimposed on it, and provides automatic-gain- 

 control bias. 



The module contains four major circuits: (1) four-stage intermediate- 

 frequency amplifier, (2) mixer-detector, (3) two-stage audio amplifier, and (4) 

 automatic-gain-control amplifier. 



* Navy Electronics Laboratory Report 1292, Environmental Test for Electronic 

 Equipment for Southern Cross, by W. R. Beye, 8 June 1965; and 



Navy Electronics Laboratory Report 1366, Combined-Environment Testing of 

 Shipboard Electronic Equipment, by F. Robinson, 7 April 1966 



