CATHODE-RAY OSCILLOGRAPH

In the radio amateur's practice the oscillograph is highly useful instrument. Oscillograph - instrument for the visual registration of pulses. Let us examine the block diagram of the oscillograph:

As can be seen from block diagram, oscillograph consists of cathode-ray tube and several blocks. The unit of amplifier Y serves for strengthening the weak input signals to the value being investigated, sufficient for the normal deflection of the beam of the tube (usually this stress it kolebletsya from 80 to 140 volts, depending on the type of tube). Scan unit serves for obtaining the saw-tooth sweep voltage, necessary for obtaining on tube face of horizontal strip. From the output of sweep oscillator the signal of saw-tooth form enters the sweep amplifier (amplifier X). The frequency of sweep oscillator is synchronized (for obtaining on the screen of the fixed picture of the investigated signal) by the supply to part of the signal to the entrance of generator being investigated. According to this principle work practically all amateurish and industrial oscillographs.

The schematic diagram of the simple low-frequency oscillograph is given below as an example:

In this oscillograph the germanium transistors of old types are used. All transistors work in the regime of avalanche breakdown. This regime is characterized by high collector nourishment, which makes it possible to considerably improve the amplifer properties of transistors. On transistor VT1 is assembled the emitter follower - for increasing the input resistance. Transistor VT2 works in the amplifier of vertical plates and ensure strengthening signal of approximately 900. On transistor VT3 is assembled the sawtooth-voltage oscillator (development). Roughly sweep frequency is regulated by switching capacitors, and it is smooth - by the variable resistor R10. from the output of sweep oscillator saw-tooth wave form enters the horizontal-deflection amplifier. This amplifier according to diagram is analogous to the amplifier of vertical plates.

Block of the tube:

This block ensures the normal modes of the work of cathode-ray tube. Resistor R1 regulates brightness, resistor R2 - focusing of ray, resistors R7 and R8 ensure the adjustment of ray respectively in the vertical and horizontal plane. The contacts of block, designated by numbers and by Latin letters are united with the appropriate contacts of other blocks.

The power source - serves for obtaining all necessary stresses:

This oscillograph, in spite of simplicity, it possesses the not bad electrical parameters and it can be used for tuning of low-frequency devices. The amplifiers of oscillograph have a passband from 20 hertz to 20-25 kilohertz. Diagram was checked by this author and showed not bad results. Diagram after assembling does not require adjusting. Sometimes it is necessary to select the version of the transistor of development, since not all transistors are capable of working in the regime of avalanche breakdown... Fixed resistors must have a power not less than 0,5 watts, with exception of resistors in the collector the circuits of the transistors of amplifiers and sweep oscillator. These resistors must have a dissipated power not less than 1 watts. Resistor R1 in the power source must have a power not less than 2 watts.

The power transformer of oscillograph has two secondary windings. Winding by 2 - filament (6,3v, with the current of 300 milliamperes) - for the nourishment of the filament circuits of tube. Winding by 3 must ensure at the output stress of approximately 280 volts with the current of load not less than 40 milliamperes.