Docking monitor Elektronika 6105 with IBM PC. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Computers

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It is no secret that some novice computer users, due to limited funds, acquire system units that are considered obsolete by modern standards. Save on the purchase of another important component of the computer - the monitor will help the proposed article. It describes a simple refinement of a black-and-white domestic monitor that allows it to be used with an IBM-compatible PC.

First of all, a monitor interface with a computer video card is made, the diagram of which is shown in the figure.

The node provides the formation of synchronization pulses of positive polarity regardless of the input polarity, and also controls the vertical image size and frame rate depending on the video mode. Different video modes use different frame rates, resulting in vertical resizing. To identify the mode, information about the polarity of the clock pulses is used.

The resistance of resistors R1 - R4 is chosen from the condition of providing the necessary low-level voltage at the inputs of logic microcircuits, without overloading the amplifiers at the output of the video card, and the capacitance of capacitors C1 and C2 is such that the voltage remains unchanged for one frame. In other words, the time constants of the R1C1 and R4C2 circuits must be much greater than the quotient 1/f, where f is the frame rate. Resistors R5 and R8 protect the inputs of the monitor chips by limiting the maximum current. Resistors R6 and R7 must be selected in such a way that the vertical size of the raster becomes the same in all video modes. Resistor R9 adjusts the frame rate.

The interface node is fed with a stabilized voltage of 5 V. The voltage of 12 V is removed from the power supply unit of the PC system unit.

The mounted node is installed inside the monitor. Pins 10 (screen), 13 (horizontal sync signal HSYNG) and 14 (horizontal sync signal VSYNG) of the VGA connector of the video card are connected directly to the interface node board. Contacts 1,2,3, transmitting a video signal, respectively, of red (R), green (G) and blue (B) colors through resistors R10 - R12 (they are installed in the VGA connector plug) with a resistance ratio of 1/2/4, are connected to the contact 12 ("Video") connector XP1 monitor.

Then finalize the monitor itself. Resistor R29 (hereinafter, reference designations are indicated according to its circuit diagram) is replaced with a 390 Ohm resistor, and a 6 kOhm resistor is soldered between the base and collector terminals of transistor VT1,5 (it will set the video amplifier operating mode).

The main frequency of the horizontal pulses is determined by the capacitor C21 (4700 pF), connected to pin 14 of the K174XA11 microcircuit. To increase the pulse frequency to 31 kHz, a KG-1 capacitor with a capacity of 2000 pF of the M47 group is installed in its place (any other such rating with a small TKE is also suitable). With an increase in the horizontal scanning frequency, the horizontal size decreases significantly (due to an increase in the reactance of the deflecting system). To obtain the maximum possible frame width, the deflecting system (OS) of the kinescope is connected to terminal 4 of the TVS. In addition, the horizontal bias resistor R46 (220 kOhm) is replaced with a 160 kOhm resistor and a resistor with a nominal value of 3 Ohms is installed in the open circuit L6 - the base of the transistor VT9.

To maintain the previous raster size when operating at an increased frequency, it is necessary to increase the supply voltage of the monitor nodes to 12 V by installing a jumper between the pads under the emitter and collector terminals of the transistor VT1. The transistor itself VT1 (KT863A), as well as VT2 (KT683E), VT3 (KT3102BM) and VT4 (KT315V or KT209) are removed.

For the same purpose, the resistor R65 (0,51 Ohm) is replaced with a jumper in the power supply circuit of the horizontal scanning output stage. To achieve the largest horizontal dimension, the elements of the linearity and horizontal dimension adjustment circuits (R66, R67, C53, C54, L7, L8) are removed. In the OS resonance circuit, capacitors C55 and C57 (both with a capacity of 4,7 microfarads) are removed, and C61 of the same rating is replaced with a capacitor with a capacity 2 ... 4 times smaller, selecting it for minimal horizontal distortion. Finally, instead of C45 (0,05 μF), a capacitor with a capacity of 1 - 2 orders of magnitude smaller is installed.

In conclusion, using special test programs (the authors used Nokia Monitor Test V1 .OA and Checkit 4.0), they check and, if necessary, adjust with adjusting resistors (R10 - frame rate, R11 - vertical size, R12 - vertical linearity, R13 - line frequency) and magnets on the neck of the kinescope geometric characteristics of the image.

Literature

1. Monitor repair. Series "Repair". Issue 12./A. V. Rodin, N. A. Tyunin, M. A. Voronov. - M.: Solon, 1997.
2. Elyashkevich S. A. ZUSTST color TVs. Reference manual. - M.: Radio and communication, 1989.
3. PC hardware. 2nd edition, revised. and additional / K. Aiden, O. Kolesnichenko, M. Kramer, X. Fibelman, I. Shishigin. - S.-Pb.: VNU-St. Petersburg, 1998.

Authors: A.Klabukov, I.Krivoshey, Kirov

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