Diagnosis tester. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Diagnosis tester. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Measuring technology

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Troubleshooting in TVs of the models UPIMCT-61 and UPIMCT-67 is greatly facilitated when using the described diagnosis tester. Connect it to the pins of the X3 connector on the cross-platform of the scanner from the side of the printed conductors. The device allows you to simultaneously control six constant and four pulse voltages in the circuits of the scanners and power supply. This speeds up the detection of defective elements that are difficult to identify only by replacing modules.

The schematic diagram of the device is shown in fig. 1. the location of the indicators on the scoreboard and their relationship - in fig. 2.

Fig.1 (click to enlarge)

Ris.2

Indicators (LEDs HL1-HL10) indicate malfunctions by turning off or changing the brightness of the glow. If the TV is working, a current of about 10 mA flows through the LEDs, and they glow the same way. Let's consider the work of each indicator. The glow of the HL6 LED indicates the presence of a voltage of 12 V. It is powered by the MZ-1-1 synchronization module, which generates a trigger pulse (ZI OH) of the flyback trinistor VT1 in the scan unit, and a number of other nodes. In the absence of this voltage (the LED is off), the specified module does not work and, as a result, constant (220, 24-18 V) and all pulse voltages are not generated (HL1, HL2, HL4. HL5, HL8-HL10 do not light up).

The burning indicator HL3 indicates the presence of a voltage of 250 V supplying the horizontal scanning (SR) output stage. SI) and personnel (KI) impulses. At the same time, the HL220 LED, which indicates a voltage of 24 V, glows weakly, since only 18 V is supplied to it through the VD4 diode of the scanner unit. The voltage of 24 V, obtained by rectifying the line scan reverse pulses, causes the HL1 indicator to light. It is necessary for the operation of the output stages of video amplifiers (VU) in the M12-220-5 modules of the signal processing unit (BOS). The absence of this voltage (LED HL2 off) leads to excessive unregulated brightness of the screen. The presence of a voltage of 4 V supplied to the vertical scanning (CR) and stabilization modules is signaled by the HL1 LED. If it is off, the operation of the MZ-5-24 vertical scan module is disrupted (the raster is much shifted down), the stabilization module may fail and, as a result, the protection device in the power supply may trip. The HL4 glowing indicator indicates the presence of a 2 V voltage supplying the amplifier module 2 (UZCH).

Without it, the audio channel does not work. If the indicators HL7 and HL6 are not lit at the same time, then this indicates the absence of an unstabilized voltage of -20 V coming from the rectifier bridge VD1 -VD4 to the modules MC-12-1 and MC-15-1 of the power supply. If the HL6 indicator is not lit when the HL7 LED is on, then the MS-15-1 (AR2) module or the 15 V power supply circuit is faulty. In their absence, the line scan output stage does not work, there are no voltages of 1, -1 V. triggering forward pulses, horizontal and vertical pulses are not generated. The HL1 indicator lights up under the action of the forward stroke trigger pulses, which are generated by the horizontal reverse stroke unit. If they are absent, there are no constant voltages of 9, 220,24-18 V, as well as horizontal and vertical pulses.

The HL2 LED goes out when there are no horizontal pulses on the secondary winding of the output transformer. In this case, the stabilization module MZ-3-1 does not work, which can lead to the operation of the protection unit and the loss of voltages of 24, -18 V and personnel pulses. The voltage - 18 V, necessary to power the vertical scan module, controls the HL8 LED. If this voltage is not present, the operation of the vertical scanning module and vertical centering are disrupted (the frame is much shifted up, sometimes beyond the screen). The HL1 indicator lights up when there are pulses at the vertical scan output. They enter the BOS and are used there to start the multivibrator in the UM2-1-1 formation module. The printed circuit board of the device is shown in fig. 3. It is designed for the installation of MLT resistors, capacitors K50-12 (C2), K73-17 (C1) and KD-1 (C3). Socket XS1 - SNP-16.

Author: Yu.Solodov

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