Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

PUSH-PULL CIRCUIT 465For calibration during the cutting of a record, the cutter is mountedin the usual way. The oscillator-discriminator unit is mounted immediatelybeside the cutter (see Figure 12). The FM plates are connectedto the oscillator and discriminator circuitsdiameter steel wires covered with vinylite insulation.by means of two 0.004-in.The ground wirebetween the two units is of the same material. The complete schematicdiagram of the calibrator is shown in Figure 13.The output of the oscillator-discriminator unit is fed to an amplifier,which is on the same chassis with the power supply. It consists of aconventional circuit using the 6SJ7 triode connected. From there theFig. 13—Schematic of the push-pull FM calibrator.signal passes through a 3-position switch which selects the "flat compensator,"the "orthacoustic," or the "no compensation" circuits. Thesepositions can be used for different purposes as follows : "No compensation"is used for measurements with a vacuum tube voltmeter, forfrequency response tests, and input versus output curves. "Flat"response can be used for monitoring on disks requiring that type ofresponse; however, the important function of this position is for intermodulationtests. "Orthacoustic" can also be used for monitoring whilethe record is being cut, and is designed for that purpose.To obtain consistent readings, it is important to have the oscillatortuned to the same frequency relative to the optimum point of operation