JPS6214882B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a magnetic head demagnetizer that instantly demagnetizes a magnetic head of a tape recorder or the like with a single touch operation. The present invention relates to a magnetic head demagnetizer that can be used.

In general, the recording and playback heads of tape recorders become magnetized after long-term use, which causes recording and playback characteristics, especially an increase in noise and deterioration of high frequencies, so periodically demagnetize the magnetic heads. It is necessary to do so.

By the way, in a stereo tape recorder, in addition to degaussing the stereo recording/playback head as described above, it is also essential to adjust the left/right balance to ensure proper recording and playback. I can't. Conventionally, for this balance adjustment, it was necessary to use a test signal for balance adjustment transmitted from a broadcasting station, or to rely on a magnetic tape cartridge for balance adjustment on which a test signal was recorded.

However, the former method has the inconvenience that the user cannot adjust the balance at any time, and the latter method requires a special magnetic tape cartridge to be prepared, making it difficult to perform the balance adjustment operation. Become passive.

In addition, instead of the latter dedicated magnetic tape cartridge, an oscillation circuit and a coil that generates a magnetic field by the oscillation circuit are housed in a cartridge of the same shape, such as the one described in Japanese Patent Application Laid-Open No. 53-95806. is proposed.

However, accurate adjustment cannot be made unless the balance is adjusted after the magnetic head is demagnetized in advance.For this reason, with the conventional type described above, the cartridge must be reloaded after demagnetization to make adjustments. In addition to being troublesome, the degaussing device and the balance adjusting device must always be stored and managed together.

This invention was made in view of the above circumstances, and it is possible not only to demagnetize a magnetic head with a simple operation, but also to apply an oscillation output of a constant amplitude to the demagnetization head, and to apply the oscillation output to the demagnetization head. Accordingly, the uniform magnetic field generated from the degaussing head can be used as a test signal for balance adjustment of a stereo tape recorder, etc., thereby providing versatility.

An embodiment of the present invention will be described below with reference to the drawings.

In the figure, 1 is a power supply battery, 2 is a power switch, and 3 is a DC booster circuit such as a DC-DC converter. , 10, a diode 11, etc., and together with the power supply battery 1, constitute a DC power supply circuit 12.

13 is a switching circuit connected to the output stage of the DC power supply circuit 12, and this switching circuit 13 includes, for example, a switching transistor 14.
16, resistors 17 to 22, a capacitor 23, a light emitting diode 24, etc., and this switching circuit 13 includes a constant voltage element 25 such as a Zener diode and a resistor 26 for level detection.
A constant voltage circuit 27 and a large capacity capacitor 28 are connected in parallel. 29 is a first oscillation circuit driven by the charge accumulated in the capacitor 28; this oscillation circuit 29 is connected to the capacitor 3;
0, 31, resistors 32, 33, output transistors 34, 35, etc., and excitation coils 36, 3.
6 and a degaussing head 38 consisting of a capacitor 37.
is connected.

39 is a second oscillation circuit that is connected to the DC power supply circuit 12 and generates an output signal with a constant amplitude;
A parallel resistance type transfer circuit 48 consisting of resistors 40 to 43 and capacitors 44 to 47, an oscillation transistor 49 having an amplifying effect, and resistors 50 to
52, a phase shift type consisting of a capacitor 53, etc.
A CR oscillation circuit is used. The output stage of the second oscillation circuit 39 is connected to the degaussing head 38 via an impedance matching circuit 60 consisting of a transistor 54, resistors 55 to 57, capacitors 58, 59, etc. The degaussing head 38 is configured to generate a uniform magnetic field for adjusting the left and right level balance of a stereo tape recorder or the like.

Next, the operation of the above configuration will be explained.

When the power switch 2 is closed, the terminal voltage of the power supply battery 1, for example 1.5V, is boosted to about 80V by the booster circuit 3. When the output voltage of the booster circuit 3 is applied to the switching circuit 13, the switching transistor 14 becomes conductive and charging of the capacitor 28 is started.

When the capacitor 28 is charged and its terminal voltage reaches a constant voltage value, for example, 15V, a reverse current suddenly flows through the constant voltage element 25 of the constant voltage circuit 27 and the coupling capacitor 23 is charged. The base pole of transistor 16 is driven and transistor 16 becomes conductive. Due to this conduction of switching transistor 16, switching transistors 14 and 1
5 become non-conductive and conductive, respectively, and the switching transistor 14 becomes non-conductive, so that the voltage application from the booster circuit 3 to the capacitor 28 side is stopped, and the switching transistor 14 becomes conductive, so that the light-emitting element 24 becomes non-conductive. It emits light to indicate that the capacitor 28 is being charged. Due to the conduction of the switching transistor 15, the resistors 21 and 2
Since the voltage generated at the connection point of 2 is input to the transistor 10 of the booster circuit 3, the current of the booster circuit 3 is limited, and the switching circuit 13 continues to operate with the minimum necessary DC voltage of about 2 to 3V. At the same time, the light emission display of the light emitting element 24 is also continuously maintained.

On the other hand, the switching transistor 14 becomes non-conductive, and the switching transistor 1
6 is made conductive, the charge stored in the capacitor 28 is discharged to the first oscillation circuit 29, and this oscillation circuit 29 is driven. The output signal from the first oscillation circuit 29 generates in the degaussing head 38 an alternating magnetic field that gradually decreases with time as the capacitor 28 discharges. Therefore, if the degaussing head 38 is set close to the recording/reproducing head of a tape recorder (not shown), the residual magnetism of this head will be reliably erased by the alternating magnetic field.

By the way, when the power switch 2 is turned on, the DC voltage from the DC power supply circuit 12 is turned on to the second voltage.
The oscillation circuit 39 operates to generate an oscillation output with a constant amplitude, for example, a 1 KHz sine wave with an amplitude of about 10 to 25 mV. When this oscillation output is applied to the demagnetizing head 38, a uniform magnetic field is generated from the demagnetizing head 38. This magnetic field is superimposed on the alternating magnetic field, and the alternating magnetic field is
Even after it is gradually reduced and attenuated by the discharge, it is output independently from the degaussing head 38 with the constant amplitude. In other words, recording with a stereo tape recorder, etc. The uniform magnetic field with a constant amplitude is input to the playback head as a test signal for adjusting the balance between the left and right levels. It is possible to adjust the balance between the left and right levels. In this case, the amplitude of the oscillation output is set to a value of about 10 to 25 mV, which is extremely small compared to the amplitude of the alternating magnetic field for demagnetization, in a state superimposed on the alternating magnetic field. This is to prevent the degaussing operation from being adversely affected. Of course, when applying the oscillation output from the second oscillation circuit 39 to the degaussing head 38, the oscillation output is applied to the degaussing head 38 with a time delay, without being superimposed on the alternating magnetic field from the degaussing head 38. It may be configured as follows.

As described above, the present invention connects a degaussing head to a first oscillation circuit driven by the accumulated charge of a large-capacity capacitor, and generates an alternating magnetic field that attenuates in accordance with the discharge time constant of the capacitor from the degaussing head. By generating the
The reproduction head can be demagnetized easily and quickly, and in particular, the oscillation output of the second oscillation circuit that generates an oscillation output with a constant amplitude is applied to the demagnetization head to generate a uniform magnetic field. Because of this, the above uniform magnetic field can be used as a test magnetic field for left and right balance adjustment of stereo tape recorders, etc., without relying on broadcast station test signals or dedicated magnetic tape cartridges as in the past. Therefore, it is possible to provide a convenient magnetic head demagnetizing device that allows a balance adjustment operation to be performed subsequent to the demagnetizing operation described above.

[Brief explanation of the drawing]

The drawing is an electric circuit diagram showing an example of a magnetic head demagnetizing device according to the present invention. 12... DC power supply circuit, 13... Switching circuit, 28... Large capacity capacitor, 29... First oscillation circuit, 38... Demagnetizing head, 39... Second oscillation circuit.

Claims (1)

[Claims] 1. A switching circuit 13 inserted between the DC power supply circuit 12 and the large-capacity capacitor 28 to control charging of the capacitor 28, and the capacitor 2
8 is charged to a predetermined voltage value, a first oscillation circuit 29 is driven by discharging the accumulated charge;
The second oscillation circuit 39 is connected to the DC power supply circuit 12 and generates an oscillation output with a constant amplitude, and the oscillation output from the first oscillation circuit 29 generates an alternating magnetic field for degaussing according to the discharge time constant. and a demagnetizing head 38 which receives the oscillation output from the second oscillation circuit 39 and generates a uniform magnetic field for balance adjustment.