60.. If this 'check or erratic operation indicates that the sound level 

 recorder is not functioning properly and the cause is not obvious (i e,, 

 a defective tube, defective condenser, etc), the solenoid-wound, magnetic 

 clutch coils should bo tested for continuity Reference to Fig<, 47 will 

 show their circuit function and give their DC resistance as approximately 

 2200 ohms, Theyr physical location in the recorder is on the under side 

 of the chassis, just above the selective clutch box, They are terminated 

 near the 6H6 diode rectifier sub panel and are accessible for continuity 

 checks, 



6l„ At the rear of each shelf containing a graphic level recorder is a 

 metal strip on which terminals are mounted B To these are brought the 

 cables containing the signal, the time index pulses, and the 115 v AC 

 supply controlled by the automatic switching unit = 



Maintena nce 



62 o Keep paper feed sprocket and guide rails free from accumulation of 

 wax and paper perforation chips. Clean them after use each day or the wax 

 will harden and interfere with the paper feed on restarting the machine. 

 Oil holes are indicated for lubrication of the motor and clutch assembly. 

 Use oil sparingly, 



63o If it is desired to remove a graphic level recorder from its shelf this 

 must be done from the rear. The front panel must be removed at the hinge 

 mounting fastened just inside the slide track on each side, the rear-ter- 

 minal strip panel must be detached, and the unit must be pushed out through 

 the back, while the latches located in each side of the sliding track are 

 held up„ 



Basic Construction a n d Operation 



64<> A brief description of the basic construction of the Power Level graphic 

 level recorder made by the Sound Apparatus Co„ may be of assistance in main- 

 taining this instrument in proper operating condition. It has three major 

 parts? 



1, Input Potentiometer o This is the measuring device; it determines 

 the db per division scale, and the dynamic range of the instrument, 



2, Automatic Operatin g fechanism ^ This consists of the AC amplifier, 

 the linear rectifier, and the DC amplifier which controls a pair of 

 motor-driven magnetic clutches operating the input potentiometer slider 

 and the writing scriber .. 



Jo Recording .Mechanism, This consists of the selective feed paper tape 

 drive system, and a clutch system to control the writing speed* of the 

 . writing scriber. 



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