the l3 system amplifiers 885 



Mechanical Design 



The mechanical assembly of the amplifier, like the configuration, 

 is divided into three main sections. The input and output amplifiers are 

 mounted on separate chassis which are designed for ready removal from 

 the main base casting. The regulating network is mounted in an enclosed, 

 shielded compartment which also serves to shield the component ampli- 

 fiers from each other. Figs. 3 and 4 show the assembled amplifier. 



Because of the wide frequency range and close control of parasitic 

 capacity and lead inductance required, the L3 amplifier was designed 

 as an integrated whole, and all networks were designed with, and as part 

 of, the amplifier. In each case circuit elements were placed in space in the"" 

 best possible position for optimum electrical performance, and support- 

 ing structures were then designed to maintain the desired space relation- 

 ships. These supporting structures are made as separate units which 

 mount on the amplifier chassis, so that the networks can be individually 

 tested before final assembly into the amplifiers, and can be removed for 

 repair of replacement if necessary. 



Heretofore, this method of design has been impracticable because 

 it results in very complicated supporting structures. It was feasible in 

 this case because of the availability of a new type of material, which 

 removes many of the mechanical design constraints. This is a cold casting 

 resin, and parts are produced in a cheap phenolic mold. Since the process 

 is practically equivalent to the sand-casting of metals, complex parts 

 can be economically manufactured even in the relatively small quan- 

 tities required for L3 production. Where necessary to assure accurate 



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Fig. 3 — Line amplifier and housing. 



