23 



. — 1& 9>X . Incoming Line Connector 



\obJ 



Main Line to Control Panel 



To Control Panel 



3 Ampere Fuses 



9~ !> 



O o o o Ground Side 



-To Amplifiers Terminal 2 



"To Amplifiers Terminal I 



Figure 10 - Schematic Diagram of 110-Volt a-c Power Distribution 



induction motors. The voltage amplifier portion consists of 4 resistance- 

 coupled stages, using twin triode 12AX7's. Cathode degeneration is used to 

 achieve stability. The power amplifier, a pentode 6AQ5. is resistively 

 coupled to the voltage amplifier section. No load is provided within the 

 amplifier for the power tube. The plate circuit is completed through the load, 

 which consists of one phase of a 2-phase induction motor, shunted by a 1 -/if 

 capacitor. 



Primary power for LVDT's is supplied by the amplifier. The phase 

 shift through the amplifier is adjusted so that the output of an LVDT is ampli- 

 fied and applied across the load, 90 degrees in phase from the power-line 

 phase. Since the second phase of the motor is connected across the power line, 

 conditions for maximum torque are thereby established. Sensitivity is rated 

 in terms of the minimum change in input to amplifier which will cause reversal 

 in direction of motor with full torque. In terms of LVDT output this is equiv- 

 alent to the minimum change in core position about null which will cause the 

 same change in motor operation. 



The rectifier power supply is transformerless. It is a grounded 

 negative-voltage doubler using selenium rectifiers. A low hum level is ob- 

 tained by attention to details such as grounding, isolation filters, and ar- 

 rangement of components. With this type of supply, one side of the power line 

 is connected to the amplifier ground. This is Terminal 1 on the front panel. 

 It is necessary that this polarity be observed in connecting a power line to 

 the amplifier. 



