SU1688282A1 - Instrument to meter playback electromotive force of the video head of the rotating heads assembly - Google Patents

Abstract

The invention relates to equipment for input quality control of video heads during mass production of 7 W //, // y,% t video recorders and reduces the time spent on measuring the electromagnetic parameters of video training and simplifies the design of the device for measuring EMF of video heads Drum 2 with magnetic tape 3 mounted on the shaft of the electric motor 1 eccentric, while the axis of rotation of the drum 2 is offset relative to its vertical axis of symmetry by half the sum of the magnitude of the nominal overhang of the working surface video head 4 for forming the drum of the rotating head unit and tolerance for it, and video head 4 is preset so that its working surface is separated from the axis of rotation of the drum 2 by a distance equal to the difference between the radius of the drum 2 and the half of the sum. 4 il. I ate from about 00

Description

figure 1

The invention relates to magnetic video recording and can be used in the design of devices for monitoring the parameters of magnetic video heads.

The purpose of the invention is to simplify the device and increase its speed.

Figure 1 shows a structural diagram of a prepositioned device; Fig. 2 shows its kinematic scheme; in Fig.3,4 - time diagrams of signals received at the control points of the device.

The device contains a motor 1, the bulk of which is eccentrically mounted drum 2 with magnetic tape 3 located on its generator, in contact with main head 4, which is connected to switch 5 connected to direct current source 6, generator 7, amplifier 8 inlet and rotary sensor 9, connected to a drum 2 and connected to a gate input of a peak amplitude detector 10, the output of which is connected to an oscilloscope 11, and an input connected to the output of amplifier 8. In addition, the figure shows (FIG. 2): limiter. Steady mounted on the base 13, in which the working head rests against the video head 4, installed in the seat of the carriage 14 (position I), which can be moved between the stops 15 and 16 by means of the handle 17.

The drum 2 of the rotating video head assembly (B C D) is mounted on the shaft of the electric motor 1 with the vertical axis of symmetry of the drum offset from the axis of the motor shaft A 25-27.5 µm, since the tolerance for departure of the working surface of the video head beyond the surface of the drum 2 is 50-55 um In this case, when the drum 2 is rotated with its axis shifted, the amount of penetration of the working surface of the video head beyond the forming surface of the drum 2 varies within the limits of the nominal outreach / e and tolerance. The mutual arrangement of the video head 4, the axis of rotation and the displacement of the latter from the axis of symmetry of the drum 2, was chosen by calculation and experimentally, based on the conditions of optimal contact of the head - the tape in the drum set of any type of video recorders determined by the diameter of the drum drum and the type of used magnetic tape. . If the axis of rotation of the drum is displaced from the axis of symmetry of the drum by a size greater than half the sum of the nominal overhang of the working surface of the video head for forming the drum and tolerance for it, then as the drum rotates, the maximum amount of video head insertion into the magnetic tape exceeds the maximum

the magnitude of the departure of the video goat in RHD. This may cause the effect of inelastic deformation of the magnetic tape, the destruction of the magnetic layer or cutting through the base of the tape.

If the axis of rotation of the drum is displaced from its axis of symmetry by an amount less than the specified one, then when the drum rotates, the amount of video head insertion into the magnetic tape does not reach the nominal value

0 departure video heads in bvg, i.e. optimum contact in the headband system is not ensured. This means that the maximum emf of the video head playback is not measured. Presetting the tested zideo head at a distance of its working surface from the axis of rotation of the drum equal to the difference between the radius of the drum and half of the sum of the nominal departure of the working surface

0 video heads for forming a drum and tolerance for it, makes it possible to observe the optimal contact of the video head and magnetic tape in the measurement process. The device works as follows,

Limiter 12 is preliminarily fixed so that its working surface is separated from a plane parallel to it, passing through the axis of rotation.

0 reel 2 equal distance

i D / A, and L R - (- + -),

where R is the radius of the drum 2;

And - the value of the nominal departure

5 video heads 4 for forming the surface in the VHF of the VCR; a - tolerance on the value A. Video head 4 is installed in the landing slot of the carriage 14, when the last

0 is moved to the stop 15, before the video head 4 comes into contact with the limiter 12. This position is fixed by vacuum suction cups (not shown). Then the carriage 14 is moved by the handle 17 up to the stop 16. This video head 5 comes into contact with the magnetic tape 3. The electronic circuit of the proposed device cyclically resumes the processes of erasing recording and playback with magnetic tape 3. The cyclical operation of the device is provided by the switch 5. pulses for which serves as a rotary sensor 9, which forms one pulse per revolution of the drum 2. Moreover, each erasure and each recording

5 is carried out in 1 vol. drum, and reproduction - for 1 - 30 rpm (the latter is not strictly regulated by p & ge and is chosen for ergonomic reasons). Erasing is carried out by applying direct current from source 6 through switch 5 and controlled video head 4. The playback signal received at the output of video head 4 goes through switch 5 to the input of amplifier 8. The amplified signal having the shape shown in Fig. 3 (pos. A) or FIG. 4 (pos. A), depending on the magnitude of the optimal overhang for a particular video head, enters the input of the peak detector 10, where it is gated with pulses of the revolving sensor 9 (FIG. 3, pos. B and FIG. 4, pos. AT). The output signal of the detector 10 (Fig. 3, Pos. B or Fig. 4. Pos. B) is displayed on the screen of the oscilloscope 11, the sweep of which is synchronized by the pulses of the revolving sensor. The maximum of the signal on the oscilloscope screen corresponds to the maximum playback emf of the video head under test.

Claims (1)

The invention The device for measuring the emf of reproduction of the video head of a rotating heads unit, containing a drum mounted on an electric motor shaft connected through a speed sensor to a switch, a video head in contact with a magnetic head 0 five 0 five a tape located on the generator surface of the drum, and connected via a switch to a recording generator, a DC source and a playback amplifier, the output of which is connected through a peak amplitude detector to an oscilloscope, where the gate input of the amplitude detector is connected to a rotation sensor, characterized in that in order to simplify the device and increase its speed, the drum with magnetic tape is mounted on the motor shaft eccentric, while the axis of rotation of the drum is shifted relative to its vertical axis of symmetry is half the sum of the nominal overhang of the working surface of the video head for forming the barabans of the rotating heads block and tolerance on it, and the video head is set so that its working surface is separated from the axis of rotation of the drum by a distance equal to the difference between the radius of the drum and half the sum of the nominal overhang of the working surface of the video head for forming the drum of the rotating heads unit and the tolerance for it / 3 / 7 2 BUT . % AT F #%