JPH0731788B2 - Video tape recorder clock detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a black detecting device for a video tape recorder, which detects clogging of a head of a video tape recorder.

[Outline of Invention]

The present invention relates to a clog detecting device for a video tape recorder for detecting clogging of a head of a video tape recorder, in which a reproduction state is set for a predetermined period when recording is started, and then a recording state is set. In the clock detection device of the video tape recorder that detects the level and detects the clock, the end of the magnetic tape is recorded by performing the clock detection only when the mode immediately before the recording pause is the recording state. It is designed so that there will be no false detection of the clock when recording is started.

[Conventional technology]

Generally, the recording head of a video tape recorder is often clogged with a head gear due to magnetic powder or the like, and when the head gear clogs, recording on the magnetic tape becomes impossible due to the recording head.

For this reason, conventionally, the clock is detected as follows before the recording state. That is, in a general video tape recorder, as shown in FIG. 2, a syscomputer (1) is constituted by a microcomputer, and a key device (2) is used.
Various commands are issued by the operation of the key, and for example, when the recording pause (pause) key or the stop key is operated from the recording state REC as shown in FIG. 3, the magnetic tape is wound for a predetermined time, for example, about 3 seconds. After returning to the original position, the recording medium is moved to the standby state or stopped in a slightly advanced state, and then, when the recording is started, the reproducing servo state is set for a predetermined time, for example, 3 seconds, and then the recording state REC is set when the servo is applied. In order to detect a conventional clock, a high frequency signal (carrier signal) is reproduced by a recording head (3) for inspecting the clock as shown in FIG. 2 during the reproduction servo period, and this reproduction high frequency signal RF is reproduced and amplified. The envelope detection circuit (5) is supplied via (4), and the output signal of this envelope detection circuit (5) is supplied to a comparison circuit (6) for comparing with a reference potential, and this envelope detection circuit (5) is supplied. ) Output signal is above this reference potential, the microcomputer (1) judges that there is no clock, and when this output signal is below the reference potential, the microcomputer (1) judges that it is a clock status, and the clock status indicator lamp It was supposed to turn on (7). Further, the system controller (1) controls the drum motor (8), the capstan motor (9), the loading motor (10), the video system, the servo system and the like.

[Problems to be solved by the invention]

However, in such a conventional clock detecting device for a video tape recorder, since the high frequency signal already recorded is reproduced at the start of recording to detect the clock, a new magnetic tape or an unrecorded magnetic tape is not recorded. At the time of recording, since the high frequency signal is not recorded on the magnetic tape when recording is started, the level of the reproduced high frequency signal RF at this time is zero, and there is the inconvenience of judging that it is in the clog state.

In view of this point, the present invention has an object to prevent erroneous detection of the clog state in the above-described claw detection device.

[Means for solving problems]

As shown in the drawing, the clock detecting device of the video tape recorder of the present invention is set to a reproducing state for a predetermined period at the start of recording and then to a recording state, and detects the high-frequency signal level during the period of this reproducing state to detect the clock. In the clock detecting device of the video tape recorder for detecting, the clock is detected only when the mode immediately before the recording pause is the recording state.

[Action]

According to the present invention, the clock is detected only when the mode immediately before the recording pause is the recording state. Therefore, the high frequency signal is always recorded when the clock is detected, and the incorrect detection of the clock is required. There is no.

〔Example〕

An embodiment of the black detecting device of the video tape recorder of the present invention will be described below with reference to the drawings.

Also in this example, as shown in FIG. 3, the reproducing servo is performed for the first predetermined period, for example, 3 seconds after the recording is started. At this time, the reproducing servo is constructed as shown in FIG. The high frequency signal RF reproduced by (3) is supplied to the envelope detection circuit (5) through the reproduction amplification circuit (4), and the detection output signal obtained at the output side of this envelope detection circuit (5) is supplied. It is supplied to a comparison circuit (6) for comparison with a reference potential, and the output signal of this comparison circuit (6) is supplied to the microcomputer forming the syscon (1). After that, a recording state is set by a command from the syscon (1), and a desired recording signal is recorded on the magnetic tape by the recording head (3). In this case, the system controller (1) is constructed in the same manner as in the prior art, and the video tape recorder operates in the same manner as in the prior art.

In this example, when inspecting this clog, it is constructed so as to operate as shown in the flow chart of FIG. That is, when the clock is inspected, it is determined whether the current mode is the recording pause state (recording waiting state) RED / P, and when it is not the recording pause state REC / P, the flag for allowing the detection of the clock is left as it is. When the current mode is the recording pause state REC / P, it is determined whether the previous mode is the recording state REC. When the previous mode is the recording state REC as shown in FIG. Sets the flag for enabling the detection of clocks to "1". At this time, when the previous mode is not the recording state REC, it is determined whether the previous mode is the recording review (playback of the recorded content), and when the recording review is performed, the clock detection permission flag is left as it is. . At this time, if it is not the record review, the flag for permitting detection of this clock is set to "0".

Next, it is judged from the recording pause REC.P whether or not the recording is started. In all cases where the recording is not started after the recording pause REC.P, the clock detection is not performed.
When recording is started from this recording pause REC.P, it is determined whether or not the flag for allowing detection of the clock is "1". When the flag for allowing detection of the clock is "0", the detection of the flag is not performed. That is, when an unrecorded magnetic tape is used, the clog detection is not performed when the magnetic tape is run due to the fast-forward state, the reproduction state, etc. and recording is started from the unrecorded portion.

When the flag for enabling the detection of the clock is "1", the clock is detected, and the output signal of the comparison circuit (6) is a high level signal "1" or a low level signal "0" in the microcomputer composing the syscon (1). If it is a high level signal "1", it is judged that it is not in a clog state, and if it is a low level signal "0", it is judged as a clog state and the clog state indicator lamp (7) is lit up. It is possible to inform the user of the video tape recorder that the magnetic head (3) is in a clog state and eliminate the recording deficiency. Since this example is configured as described above, the clock can be detected during the reproduction servo period at the time of recording start, and the recording deficiency due to the clogging of the head cap of the magnetic head (3) can be eliminated, which is convenient. Further, in this example, the clock is detected only when the mode immediately before the recording pause REC / P is in the recording state. Therefore, a high frequency signal is always recorded when the clock is detected. When there is no detection and an unrecorded magnetic tape is used, or when recording is started from an unrecorded portion of the magnetic tape, there is an advantage that the clock detection is not performed and an erroneous detection is not performed.

It should be noted that the present invention is not limited to the above-described embodiments, and needless to say, various other configurations can be adopted without departing from the gist of the present invention.

〔The invention's effect〕

According to the present invention, a clock can be detected during the reproduction servo at the time of recording start, and there is an advantage that recording deficiency due to clogging of the magnetic head (3) can be eliminated, and a mode immediately before the recording pause. Since the clock is detected only in the recording state, the high frequency signal is always recorded when the clock is detected, and there is an advantage that there is no erroneous detection of the clock.

[Brief description of drawings]

FIG. 1 is a diagram used to explain one embodiment of a clock detecting device for a video tape recorder of the present invention, and FIG. 2 is a configuration diagram showing an example of a clock detecting device for a video tape recorder.
The drawings are diagrams for explaining the present invention. (1) is a system controller, (2) is a key device, (3) is a head, (4) is a high-frequency regenerative amplifier circuit, (5) is an envelope detection circuit, (6) is a comparison circuit, and (7) is a clock state. It is an indicator lamp.

Claims (1)

[Claims] 1. A clock detection for a video tape recorder in which a reproduction state is set for a predetermined period when recording is started, and then a recording state is set, and the level of a high frequency signal is detected during the reproduction state to detect a clock. A device for detecting a clock in a video tape recorder, wherein the device detects the clock only when the mode immediately before the recording pause is the recording state.