24 



2. Installation and Operation 



Three operating controls are provided. The power switch disconnects 

 the amplifier proper from Terminals 1 and 2. The calibrate switch is used 

 when two LVDT's are connected in a null-balance system. It shorts out the sec- 

 ondary of the actuating LVDT and changes the circuit .from a null-balance sys- 

 tem to a null-seeking system. The gain control, available through an access 

 hole in the front panel, is used to limit the sensitivity to prevent hunting. 



No adjustments are required to place the Type 60AD-1 in operation 

 other than to make connections as shown in Figure 11. However, in the 60AD-2 

 the internal hum balance control must be adjusted. This is done as follows: 

 With the normal output load connected across Terminals 3 and 4, connect a 

 250-v a-c meter across these terminals. Connect a jumper from Terminal 13 to 

 14. Adjust the control until a minimum voltage is observed on the meter. 



3. Maintenance 



Since subassembly construction is used, replacement of parts in 

 maintenance is simplified. The amplifier chassis or the condenser support 

 bracket may be removed from the amplifier panel by unsoldering a few easily 

 located connections. The component board in the amplifier chassis can be 

 freed from the chassis by loosening four screws. Slack in the leads will per- 

 mit partial withdrawal of this board to allow access to the components. 



The first voltage amplifier stage is somewhat sensitive to heater 

 induced hum. It would be difficult to select a replacement 12AX7 for this lo- 

 cation unless an oscilloscope were available. A supply of replacement 12AX7's 

 is maintained by the manufacturer. In ordering a 12AX7 it is necessary to 

 state the type of amplifier and whether used for Stages 1 and 2 or 3 and 4. 



An oscilloscope is used to select the first stage tube by connecting 

 the scope across Terminals 3 and 4 and connecting a jumper from Terminal 13 

 to 14. The wave shape observed must be free from sharp points (caused by over- 

 loading due to hum input). The a-c voltage measured at Terminals 13 and 14 

 should be less than 50 volts. The hum control in Type 60AD-2 must be rotated 

 to minimize the output. 



4. Specifications 



Line voltage - 117-v 60 cycles 



Power consumption - 40 va (not including line powered phase 

 of motor) 



Sensitivity - 60AD-1 - Complete reversal for 0.00015-inch 



core motion of Type 100S Schaevitz 

 LVDT 



60AD-2 - Complete reversal for less than 0.0001- 



inch core motion of Type 100S Schaevitz 

 LVDT 



