JPS5927614A - Adjusting device of afc circuit - Google Patents

Abstract

PURPOSE:To attain simply and efficiently the adjustment, by displaying an AFC voltage together with a limit voltage. CONSTITUTION:The AFC voltage is extracted from a terminal 7 of a television receiver 1, a switch 6 is opened at first and a reference volage V is measured with a voltmeter 9. Then, a signal having an intermediate frequency f0 is applied to an intermediate frequency amplifier circuit 3 from a reference oscillator 12 to discriminate the propriety of a discriminated output voltage from a frequency discriminating circuit 4 in this case. Then, a switch 15 is closed in advance to store the reference voltage V to a storage circuit 16 and a limit voltage V+ or -DELTAV is outputted from a limit setting circuit 17. Further, the switch 6 is closed and the discriminated output voltage is applied to voltage comparators 18, 19, 20 to discriminate the propriety.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an adjustment device that can be used to adjust an AFCi circuit in a receiver having an A10 circuit, such as a television receiver.

Conventional configuration and its problems In a television receiver having a more advanced AFC circuit, the AFC is performed by superimposing the discrimination output voltage of the frequency discrimination circuit that detects the frequency deviation of the intermediate frequency signal on the reference voltage.
In a receiver where ○ is applied as a voltage to the tuner.

In order to make the AFC operation accurate, it is necessary to adjust the discrimination center frequency in the frequency discrimination circuit so that it exactly matches a predetermined center frequency.

For this reason, the adjustment status is checked at the final stage of the receiver manufacturing process, and if the adjustment is incorrect, it is readjusted to make it correct. However, in the past, such adjustment In order to check the AFC voltage, the operator had to read the AFC voltage using a voltage gauge and print out the measured value to judge whether the adjustment condition was good or not. There was an inconvenience that it lacked.

OBJECTS OF THE INVENTION The present invention solves the above conventional drawbacks and provides an AFC that synthesizes a reference voltage and a frequency discrimination output voltage to obtain an AFC voltage.
To provide an adjustment device capable of efficiently, accurately and clearly displaying the adjustment state of an AFC circuit in a receiver equipped with the circuit, and facilitating adjustment.

Structure of the Invention In the present invention, the reference voltage of the AFC circuit is detected from the receiver, and based on this, limit voltages corresponding to the allowable upper and lower limits of the center value of the AFC voltage are created. By comparing the AFC voltage when the frequency signal is applied with this limit voltage, it is determined that the adjustment state is good if the AFC voltage at this time is within the allowable range,
If it is not within the allowable range, it is determined that the adjustment condition is poor.

The feature is that this is displayed.

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

In FIG. 1, 1 is a television receiver to be adjusted, 2 is its tuner, 3 is its intermediate frequency amplification circuit, 4 is its AFC frequency discrimination circuit, and 5 is its AFC.
A voltage dividing resistor 6 is used to create the reference voltage (■), and 6 is a switch that switches whether or not to perform AFC operation.0When performing AFC operation, switch 6 is closed and the 1-frequency discrimination output voltage V is combined with the reference voltage V. (V+v) is the AFc voltage, which is applied to the tuner 2. In this case, even if the design value of the reference voltage (2) is vo, it may actually change somewhat due to variations in the voltage dividing resistor 6.

Further, the center value VO of the one-round one-number discrimination output voltage V changes depending on the adjustment state of the frequency discrimination circuit 4.

Therefore, in this device, the AFC voltage is taken out from the terminal 7 of the television receiver 1, and ! , and detects the reference voltage V among them to determine whether it is within a predetermined range. 8 is the confirmation circuit for that purpose, i! First, the reference voltage V created by the voltage dividing resistor 6 is measured with the digital voltmeter 9 while the switch 6 is open. Then, the digital voltmeter 9 converts the reference voltage ViA/D, and the converted output is converted into a tolerance range C which is stored in advance in the comparator 10.
VO±ΔTo) to determine whether it is within the allowable range. According to the judgment output, if the 1 display 11 is within the allowable range, the blue lamp is turned on.

If not, it will be displayed by lighting a red lamp, etc.

If this reference voltage V is not within the allowable range, the product is determined to be defective at this stage. If the reference voltage is within the allowable range, a signal with a predetermined accurate intermediate frequency fo is generated from the reference oscillator 12 and applied to the intermediate frequency amplifier circuit 3 from the terminal 13 of the television receiver 1. It is confirmed whether the discrimination output voltage v□ from the frequency discrimination circuit 4 is correctly outputted with respect to the intermediate frequency. Reference numeral 14 is a confirmation circuit for this purpose. At this time, first, the switch 16 is closed for a short time and the reference voltage V confirmed as described above is transferred to the memory circuit 1.
6. The switch 15 and the memory circuit 16 may be ordinary pull/hold circuits. Furthermore, this stored reference voltage v6 is used.

A limit voltage ■±ΔVi corresponding to the upper and lower limits allowable for the center value of the AFC voltage with respect to the reference voltage V is created by the limit setting circuit 17. After that, the switch 6f of the television receiver 1 is closed and the discrimination output voltage v of the frequency discrimination circuit 4 is
'1 Add to reference voltage V. This frequency discrimination output voltage V has a figure-8 curve characteristic in which the center value, that is, the discrimination output voltage vo at a predetermined intermediate frequency fo, is 0 volts if the 1-frequency discrimination circuit 4 is adjusted correctly. If there is a deviation, the discrimination output voltage V will be (0±
However, this discrimination output voltage V
is added to the reference voltage V to form the AFC voltage, so in order to detect the adjustment state of the frequency discrimination circuit 4 based on the AFC voltage taken out from the terminal 7, the reference voltage vl is used as the reference. Since the AFC voltage must be determined and the reference voltage (2) varies depending on the voltage dividing resistor 6 as described above, the memory circuit 1
6 is stored in memory. Therefore, the AFC voltage at fo when the switch 6 is closed is added to the voltage comparator 1B, 19.20, and it is detected whether or not it is within the tolerance range (V±△V) of the center value. , the lower limit voltage (V-ΔV) and a sufficiently smaller voltage v1 are applied to the voltage comparator 1B, and the upper limit voltage (V+△V) and the lower limit voltage (V-△V) are applied to the voltage comparator 19. , and the upper limit voltage (V+Δ■) and a voltage v2 that is sufficiently larger than the upper limit voltage (V+Δ■) are applied to the voltage comparator 2o, and each voltage comparator 1
8 to 20 generate a detection output only when the FC voltage is within the range of their applied voltage.
In this embodiment, each voltage comparator 18-20 further divides the applied voltage range into six ranges a-e.
A detection output is generated from only one of a to e depending on the magnitude of the FC voltage, and a display element 21 such as a light emitting diode in which these outputs are sequentially arranged.
In addition to 22.23, if the display color of 1 display element 21 and 22.23 is made different when the OC is displayed by lighting up based on the detection output, an easy-to-understand display can be made.0 Therefore, the frequency of the television receiver 1 If the discriminator 4 is properly adjusted and the AFC voltage characteristics are as indicated by the solid line in FIG.

At fo, V=O and the AFC voltage becomes V, so a detection output is generated at C of the voltage comparator 19.

C of the display element 22 is lit to indicate that the adjustment state is correct.

On the other hand, the adjustment of the frequency discrimination circuit 4 is △f toward the lower frequency.
If there is a deviation by 0.05, V=△v□ at fo, as shown by the broken line in FIG. At this time, if the amount of deviation exceeds the allowable range, △ma 0>△V, a detection output is generated from, for example, b of the voltage comparator 2o, and b of the display element 23 is lit, and the deviation is shifted to a lower frequency. Therefore, at this time, the operator looks at this display and changes the frequency discrimination circuit 4f accordingly:
Readjust so that C of the display element 22 is lit.

That is, the adjustment may be made so as to obtain the characteristics shown by the solid line in FIG.

Effects of the Invention As described above, according to the present invention, even when the reference voltage of the AFC voltage of the receiver varies, the reference voltage is memorized and a limit voltage is created based on this, and a predetermined intermediate frequency is set. Since the FC voltage when a signal of It is possible to carry out adjustment work efficiently and accurately.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an AFC circuit adjustment device according to an embodiment of the present invention, and FIG. 2 is a characteristic diagram for explaining its operation. ...Tuner, "4...Frequency discriminator, 6...
・Voltage dividing resistor, 6... Switch, 7.13...
...terminal, 14...confirmation circuit. 16... Switch, 16... Memory circuit, 17... Limit setting circuit -18, 19, 20.
...Voltage comparator. 21.22.23...Display element. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 AFCt anti-

Claims (1)

[Claims] A voltage 1 which is a combination of a predetermined reference voltage and a frequency discrimination output voltage of an intermediate frequency signal is applied to a tuner as a hyc voltage.The reference voltage and the frequency discrimination output voltage are taken out from a receiver having a FC circuit and Limit voltages corresponding to the upper and lower limits of the allowable range of the center value of the AFC voltage are created based on the above reference voltage, and the above AFC voltage and the above limit voltage are calculated when a signal of a predetermined intermediate frequency is applied to the receiver. is compared with a voltage comparator and the AF at that time is
An AFC circuit adjustment device characterized in that it displays whether or not the center value of the C voltage is within the above-mentioned allowable range.