is selected for full signal wave conditions from the wave gage. The . 

 other indicates the current in the record head from the bias signal, 

 and is normally adjusted to provide a reading of 0.8 volt which corre- 

 sponds to 8 milliamperes of bias current in the recorder tape head. 



2. Fabrication of Magnetic Tape Recorder 



Parts required for the CERC LW-1 tape recorder are listed in 

 Table X. Details of fabrication are shown in Figures 42 through 45. 



The mechanical items should be assembled to the chassis and panel 

 assembly. Particular care is required in aligning each electric motor 

 shaft and the driven shaft. Use of 1/4-inch rod drilled with a 3/16- 

 inch hole in one end through the panel bearings should aid in getting 

 good alignment of the motor shafts. Use of a similar rod drilled with 

 a 1/8-inch hole in one end should aid in aligning the calibrating signal 

 drive motor (15 r.p.m.) with the synchro shaft. When the proper alignment 

 is reached, the flexible couplings should receive the driven shafts 

 without binding. Binding at this point will cause early failure of the 

 flexible coupling. The panel shaft bearings should be cleaned, and given 

 a drop of light oil during assembly. 



Wiring of the recorder is shown on the schematic diagram on Figure 

 46. The wiring placement is not critical in obtaining proper operation. 

 Good wiring practice is all that is required. 



The constant-voltage transformer is mounted in the left rear of the 

 recorder cabinet. Input and output cables must be installed on the 

 transformer to provide proper connection to the plugs on the rear of the 

 recorder chassis. 



A signal cable for the tape recorder is fabricated to the desired 

 length using 2-conductor No. 18 AWG and two amphenol No. 80-MC2-M 

 connectors. 



Care is required in connecting the outer terminals of the three 

 potentiometers on the front panel to provide increased signal conditions 

 when the potentiometer shafts are turned clockwise. 



The tape-supply spool shaft uses a spring and washer assembly to 

 provide tension to the tape. The tension of this spring should be 

 adjusted to provide a very light pull on the unwinding tape. If too 

 little tension is applied to the rewinding tape, the tape will skew on 

 the capstan and foul the tape drive. Correct tension is just above that 

 required to prevent tape skew. 



Ferrous parts used in the tape transport, including the recording 

 head, should be demagnetized after assembly. If the tape head is mag- 

 netized, or if the tape is placed close to a magnetized object, the tape 

 recording will be of poor quality or may even be erased. 



Text resumes on page 93. 

 85 



