JPH0430642Y2 - - Google Patents

Description

[Detailed description of the invention] Target of the invention The invention relates to an erasing circuit for a tape recorder.
In particular, it relates to an erasing circuit that can perform AC erasing and DC erasing.

Purpose of the invention The purpose of the invention is to switch the mode of a tape recorder so that erasing using an AC oscillation circuit (AC erasing) is performed during recording, and erasing using a DC circuit (DC erasing) when running the tape at high speeds such as rewinding. It is an object of the present invention to provide an erasing circuit for a tape recorder that can easily switch between AC erasing and DC erasing in an erasing circuit performed in an erasing head.

Conventional technology and its problems Conventionally, permanent magnets with a simple circuit configuration have been used to erase signals used in so-called office tape recorders that record conversations and people's voices for typed manuscripts. There are erasers and erasers using DC circuits (DC erasers), but since these erasers are based on saturation magnetization caused by direct current, they are accompanied by eraser noise, and users (typists, etc.) have relatively poor S/N ratios. I had no choice but to use it due to the condition. In order to reduce such erasure noise, today's home tape recorders generally perform erasure using an AC oscillation circuit (AC erasure) to solve this problem.

On the other hand, with the above-mentioned office tape recorder, the operation of recording again, stopping, and recording again is relatively often repeated on the already recorded tape, so there is a continuous recording between one recorded part of the tape and that part. If the signal is not completely erased at the boundary with the next recorded part, or if the signal is not completely erased at the beginning of erasing, parts that are not erased or are not erased enough. There was a problem with this.

For this reason, when using an already recorded tape in an office tape recorder, a high-speed tape running operation mode such as tape rewinding is used, and signals can be erased as necessary even in this mode. In this way, the recorded signal can be erased in advance in a short time, and when recording,
In some cases, this data is further erased while recording. However, when such high-speed erasing is performed by AC erasing as described above, the tape running speed is 10 to 20 times faster than the tape running speed during normal recording, so the zero of the erasing alternating magnetic field is Erase failure occurs due to lack of convergence. Therefore, in the case of high-speed erasing, DC erasing is performed,
A solution to this problem is being considered.

It is advantageous to configure an erase circuit that performs the AC erase and DC erase as described above using the same erase head, but in order to do this, it is necessary to configure an AC erase oscillator circuit and a DC erase circuit. It is necessary to separately provide an AC erase current and a DC erase current supplied to the erase head using a mechanical changeover switch or the like to switch between the AC erase current and the DC erase current immediately before the erase head to which the erase current is supplied.

FIG. 2 is an example of a circuit using the above-mentioned mechanical changeover switch.

In the same figure, the AC erase control terminal 11 is a resistor.
Connected to the base of switching transistor _Tr11 via _R11 . The collector of the transistor Tr ₁₁ is connected to the power supply +B, and the emitter of the transistor Tr ₁₁ is connected to the intermediate terminal P ₁ of the primary coil (oscillation coil) L ₁₁ of the transformer T ₁ via _the resistor R 13. One terminal of the primary coil L ₁₁ of T ₁ is connected to the base of the oscillation transistor Tr ₁₃ via a positive feedback resistor R ₁₄ , and the primary coil L ₁₁
The other terminal of the transistor Tr ₁₃ is connected to the collector of the transistor Tr 13, both terminals of the primary side coil L ₁₁ are connected to each other via the oscillation tuning capacitor C ₁₁ , and the emitter of the transistor Tr ₁₃ is grounded.

14 is a mechanical changeover switch, one of the changeover terminals a is connected to the power supply +B via the erase current adjustment resistor _R15 , and the other changeover terminal b is connected to the transformer.
It is connected to one terminal of the coil L ₁₂ on the secondary side of T ₁ . Further, the other terminal of the coil L ₁₂ on the secondary side of the transformer T ₁ is grounded. A common terminal c of the changeover switch 14 is connected to the erase head 13.

In the configuration circuit shown in FIG. 2 above, in the case of AC erasure, the movable contact of the changeover switch 14 is
When the DC control signal is input to the AC erase control terminal 11 in this state, the switching transistor, which had been in the cut-off state, is switched to the cut-off state.
Tr ₁₁ is turned on, current is supplied from power supply +B,
The primary coil of the transformer T ₁ through the resistor R ₁₃
A current is supplied to the intermediate terminal P ₁ of L ₁₁ . The primary coil _L11 of this transformer _T1 and the oscillation transistor
The AC oscillation circuit consisting of Tr ₁₃ , oscillation tuning capacitor C ₁₁ , and positive feedback resistor R ₁₄ operates when the above-mentioned current is supplied, and supplies AC erase current to erase head 13 via changeover switch 14. do.
Further, the oscillation frequency of the AC erase current is adjusted by the tuning capacitor _C11 .

In addition, in the case of DC erasure, when the movable contact of the changeover switch 14 is switched to the changeover terminal a side, the power +B
A resistor R ₁₅ adjusts the erase current to supply the appropriate DC erase current to the erase head 13 via a changeover switch 14 .

However, in the case of the circuit shown in FIG. 2 as described above, switching the erase current by the mechanical changeover switch 14 immediately before the erase head may cause noise, or the setting location of the changeover switch may be incorrect. However, there were various problems, such as the circuit configuration being considerably complicated due to restrictions on the circuitry, which increased costs, and so on.

Therefore, in order to solve the above problems, the second
FIG. 3 shows an example of a circuit using an electronic changeover switch instead of the mechanical changeover switch shown in the figure.

In Fig. 3, 21 is an AC erase control terminal;
2 is a DC erase control terminal, and AC erase control terminal 21 is connected to a switching transistor via a resistor _R21 .
While it is connected to the base of Tr ₂₁ , it is also connected to the base of switching transistor Tr ₂₄ via a resistor R ₂₆ . The collector of the transistor Tr ₂₁ is connected to the power supply +B, and the emitter of the transistor Tr ₂₁ is connected to the intermediate terminal P ₂ of the primary coil (oscillation coil) L ₂₁ of the transformer T ₂ via the resistor R ₂₃ .
One terminal of the primary coil L ₂₁ of the transformer T ₂ is connected to the base of the oscillation transistor Tr ₂₃ via a positive feedback resistor R ₂₄ , and the other terminal of the primary coil L ₂₁ is connected to the base of the oscillation transistor Tr 23 via the positive feedback resistor R ₂₄ . connected to the collector,
The emitter of transistor Tr ₂₃ is grounded.

The collector of transistor Tr ₂₄ is connected to the power supply +B, and the emitter of transistor Tr ₂₄ is connected to resistor R ₂₇
is connected to the base of the switching transistor Tr ₂₅ through a resistor R 28 , and connected to the base of the switching transistor Tr ₂₆ through a resistor R ₂₈ .

The collector of the transistor _Tr25 is connected to one terminal of the coil _L22 on the secondary side of the transformer _T2 .
The other terminal of the secondary coil _L22 of the transformer _T2 is grounded.

Emitter and transistor of transistor Tr ₂₅
The emitters of transistor Tr ₂₆ are connected to each other, and the collector of transistor Tr ₂₆ is connected to erase head 23.

On the other hand, the DC erase control terminal 22 is connected to the base of a switching transistor Tr22 via a resistor _{R22 ,} and the emitter of the transistor _Tr22 is connected to the erase head ₂₃ via an erase current adjusting resistor R25. The collector of transistor _Tr22 is connected to power supply +B.

In the configuration circuit shown in FIG. 3 above, when a DC control signal is input to the AC erase control terminal 21, the switching transistor that has been in the cut-off state until then is switched off.
Tr ₂₁ and Tr ₂₄ are each turned on (at this time, the switching transistor Tr ₂₂ , which will be described later, is in a cut-off state), and current is supplied from the power supply +B.
The primary coil of the transformer T ₂ through the resistor R ₂₃
A current is supplied to the intermediate terminal P ₂ of L ₂₁ .

Furthermore, when the switching transistor Tr ₂₄ is turned on, the voltage of the power supply +B is applied to the transistors Tr ₂₅ ,
These transistors Tr ₂₅ , which are applied to the bases of Tr ₂₆ and previously in the cut-off state,
Tr ₂₆ is turned on.

AC composed of primary coil L ₂₁ of transformer T ₂ , oscillation transistor Tr ₂₃ , and positive feedback resistor R ₂₄
The oscillation circuit operates by being supplied with current from the power supply +B, and supplies an AC erase current to the erase head 23.

Furthermore, when the DC control signal at the AC erase control terminal 21 is cut off and the DC control signal is input to the DC erase control terminal 22, the switching transistor
Tr ₂₂ is turned on (at this time, the aforementioned switching transistors Tr ₂₁ and Tr ₂₄ are in the cut-off state), current is supplied from the power supply +B, and the resistor R ₂₅
The erase current is adjusted by the erase head 23 to provide an appropriate DC erase current to the erase head 23.

However, in the case of the circuit shown in FIG. 3 as described above, the switching transistors Tr ₂₂ , Tr ₂₅ ,
Since Tr ₂₆ needs to be of a high voltage type in consideration of the voltage during AC oscillation, there is a problem in that the cost increases significantly.

Key Points of the Invention In order to solve the above-mentioned problems and achieve the purpose of the invention, the first control terminal [1] is connected to the base of the first transistor [Tr1], and the first control terminal [1] is connected to the base of the first transistor [ _Tr1 ].
The emitter of the transistor [Tr ₁ ] is connected to the intermediate terminal [P] of the primary side [L ₁ ] of the transformer [T], and one terminal of the primary side [L ₁ ] of the transformer [T] is connected to the resistor [Tr 1 ]. R ₄ ] to the base of the second transistor [Tr ₃ ], and the other terminal is connected to the base of the second transistor [Tr 3 ].
is connected to the collector of the transistor [Tr ₃ ],
Both terminals of this primary side are connected to each other via the first capacitor [C ₁ ], the emitter of the second transistor [Tr ₃ ] is grounded, and the second control terminal [2] is connected to the third The emitter of the third transistor [Tr ₂ ] is connected to the base of the transistor [Tr ₂ ], and the emitter of the third transistor [Tr 2 ] is connected to one terminal of the secondary side [L ₂ ] of the transformer [T] and the second capacitor [C _{2 ]} . ], the other terminal of the secondary side [L ₂ ] of the transformer [T] is connected to the erase head [3], and the first and third transistors [Tr ₁ , Tr ₂ ]
The collectors of each are configured to be connected to the power supply [+B], and when a signal is supplied from the first control terminal [1], the first transistor [Tr ₁ ] becomes conductive, thereby causing the erase head [+B] to be connected to the power supply [+B]. 3] is supplied with an AC erase current and a signal is supplied from the second input control terminal [2], the third transistor [Tr ₂ ]
is conductive to the erase head [3].
A DC erase current is supplied, and by switching the signals supplied to the first and second control terminals [1, 2], the AC erase current and DC erase current supplied to the erase head [3] are switched. The present invention provides an erasing circuit for a tape recorder characterized by the following.

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

FIG. 1 is a circuit diagram showing an embodiment of an erasing circuit for a tape recorder according to the present invention.

In the figure, 1 is an AC erase control terminal that controls the AC erase signal during recording, and 2 is a DC erase control terminal that controls the DC erase signal during high-speed tape running.
AC erase control terminal 1 is connected to the base of switching transistor Tr ₁ via resistor R ₁ . The emitter of the transistor Tr ₁ is connected to the intermediate terminal P of the primary coil (oscillation coil) L ₁ of the transformer T via the resistor R ₃ , and one terminal of the primary coil L ₁ of the transformer T is It is connected to the base of the oscillation transistor Tr ₃ via the positive feedback resistor R ₄ , and the other terminal of the primary side coil L ₁ is connected to the collector of _the transistor Tr ₃ . The terminals are connected to each other via an oscillation tuning capacitor _C1 , and the emitter of the transistor _Tr3 is grounded.

On the other hand, the DC erase control terminal 2 is connected to the base of the switching transistor Tr ₂ via the resistor R ₂ , and the emitter of the transistor Tr ₂ is connected to the secondary coil of the transformer T via the erase current adjustment resistor R ₅ . The secondary coil L ₂ is connected to one terminal of the coil L 2 and grounded via the erase noise prevention capacitor C ₂ , and the other terminal of the secondary coil L ₂ is connected to the erase head 3 . Further, the collectors of the transistors Tr ₁ and Tr ₂ are each connected to the power supply +B.

Next, the operation of the above-mentioned constituent circuit will be explained.

In the figure, when a DC control signal for switching the electronic switch is input to the AC erase control terminal 1, the switching transistor Tr ₁ , which has been in the cut-off state, is turned on (at this time, the switching transistor Tr ₂ , which will be described later), is turned on. (in the cut-off state), current is supplied from the power supply +B, and current is supplied to the intermediate terminal P of the coil L ₁ on the primary side of the transformer T via the resistor R ₃ . AC composed of the primary coil _L1 of this transformer T, the oscillation transistor _Tr3 , the oscillation tuning capacitor _C1 , and the positive feedback resistor _R4 .
The oscillation circuit operates when the above-mentioned current is supplied, and supplies an AC erase current to the erase head 3.
Further, the oscillation frequency of the AC erase current is adjusted by the tuning capacitor _C1 .

Furthermore, when the DC control signal at the AC erase control terminal 1 is cut off and the DC control signal is input to the DC erase control terminal 2, the switching transistor Tr ₂
is turned on (at this time, the aforementioned switching transistor Tr ₁ is in the cut-off state), and the power supply +
A current is supplied from B, and the erase current is adjusted by resistor R ₅ to supply an appropriate DC erase current to the erase head 3 via the secondary coil of the transformer T. Also, the erase head 3 is connected to the capacitor _C2 .
Erasing noise that occurs in the process is prevented.

As described above, when a DC control signal is input to AC erase control terminal 1, the AC oscillation circuit operates,
When an AC erase current is supplied to the erase head 3 and a DC control signal is input to the DC erase control terminal 2, a DC erase current is supplied to the erase head 3.

Therefore, by switching the DC control signals supplied to these two AC and DC erase control terminals 1 and 2 in accordance with the mode switching of the tape recorder, the AC erase current supplied to one erase head 3 can be changed. and DC erase current can be switched and supplied. In addition, these erase currents can be switched by switching between an AC erase current and a DC erase current that are supplied to one erase head from separate circuits using a mechanical changeover switch or the like just before the erase head to which the erase current is supplied. This is not done by switching the DC control signals supplied to the two AC and DC erase control terminals 1 and 2 of one erase circuit, so the erase current immediately before the erase head is This eliminates the need for a mechanical changeover switch, simplifies the circuit configuration, and reduces costs.

Furthermore, due to the addition of the capacitor _C2 to the switching transistor _Tr2 , high voltage is not applied even when AC is erased.
A normal type transistor can be used instead of a high voltage type, and the cost will not increase.

Incidentally, when erasing the signal is unnecessary, such as during normal playback of a tape recorder, the supply of the erasing current to the erasing head may be stopped by, for example, turning off the power to the erasing circuit.

Effects of the invention The erasing circuit of the tape recorder of the present invention has the above circuit configuration, and is an erasing circuit that performs AC erasing during recording and DC erasing during high-speed tape running such as rewinding, using the same erasing head. In,
This switching between AC erasure and DC erasure can be easily configured, and the erasure current can be switched simply by switching the small current DC control signal supplied to the base of the switching transistor of the erasure circuit. Since there are no restrictions on location, it can be performed anywhere, eliminating the need for a comparatively large current changeover switch just before the erase head, reducing costs, and furthermore, the switching transistor for changeover can be a normal type transistor. It has the advantage of not increasing the cost and not increasing the cost.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of an erasing circuit for a tape recorder according to the present invention, and FIGS. 2 and 3 are circuit diagrams showing examples of erasing circuits for a conventional tape recorder. 1... AC erase control terminal, 2... DC erase control terminal, 3... erase head, C ₁ ... oscillation tuning capacitor, C ₂ ... erase noise prevention capacitor, L ₁ ...
...The primary side coil of the transformer T (oscillation coil),
L ₂ ... Secondary coil of transformer T, P ... Intermediate terminal, R ₁ , R ₂ , R ₃ ... Resistor, R ₄ ... Positive feedback resistor, R ₅ ... DC erase current adjustment resistor, _Tr1 , _Tr2 ...
...Switching transistor, Tr ₃ ...Oscillation transistor, T...Transformer.

Claims (1)

[Scope of utility model registration request] The first control terminal is connected to the base of the first transistor, the emitter of the first transistor is connected to the intermediate terminal of the primary side of the transformer, and one terminal of the primary side of the transformer is connected to the base of the first transistor. and the other terminal is connected to the collector of the second transistor, both terminals of this primary side are connected to each other via the first capacitor, and the other terminal of the primary side is connected to the base of the second transistor. The emitter of the transistor is grounded, the second control terminal is connected to the base of a third transistor, and the emitter of the third transistor is connected to one terminal of the secondary side of the transformer and a second capacitor. The other terminal of the secondary side of the transformer is connected to the erase head, the collectors of the first and third transistors are connected to a power supply, respectively, and the first control terminal When a signal is supplied to the erase head, the first transistor becomes conductive, thereby supplying an AC erase current to the erase head;
When a signal is supplied from the second input control terminal, the third transistor becomes conductive, thereby supplying a DC erase current to the erase head,
is supplied to the erase head by switching the signals supplied to the first and second control terminals.
An erasing circuit for a tape recorder characterized by switching between an AC erasing current and a DC erasing current.