Small size and low cost, the oscilloscope C1-94 especially convenient for repair services of electronic radio equipment, as well as for radio amateurs and educational institutions.
Many specialists, and especially radio amateurs, are well aware of the S1-94 oscilloscope. The oscilloscope, with its rather good technical characteristics, has very small dimensions and weight, as well as a relatively low cost. Thanks to this, the model immediately gained popularity among specialists involved in the mobile repair of various electronic equipment, which does not require a very wide input signal bandwidth and the presence of two channels for simultaneous measurements.
Main technical characteristics of the C1-94 device:
Bandwidth: 0-10 MHz.
HR rise time: 35 ns.
Rejection coefficient: 10 mV / div - 5 V / div.
Limits of the basic error of the coefficients of deflection and sweep: ± 6%.
Sweep factor: 0.1 μs / div - 50 ms / div.
Input impedance, capacitance:
1 MOhm, 40 pF;
10 MOhm, 25 pF (with external divider 1:10).
Indicator type: CRT 8LO7I.
Working part of the screen: 40x60 mm.
Power supply: 220 ± 22 V, 50 ± 0.5 Hz or 240 ± 24 V, 60 ± 0.6 Hz.
Power consumption: 25 V * A.
Zakharychev E.V., design engineer
The differentiated signal is fed to the trigger circuit, which, together with the sweep generator and the blocking circuit, provides the formation of a linearly varying sawtooth voltage in the standby and self-oscillating modes.
The triggering circuit is an asymmetric trigger with emitter coupling on transistors T22-UZ, T23-UZ, T25-UZ with an emitter follower at the input of the transistor T23-UZ. The initial state of the starting circuit: the T22-UZ transistor is open, the T25-UZ transistor is open. The potential to which the capacitor C32-UZ is charged is determined by the collector potential of the T25-UZ transistor and is approximately 8 V. The D12-UZ diode is open. With the arrival of a negative pulse at the T22-UZ base, the triggering circuit is inverted, and a negative drop on the T25-UZ collector blocks the D12-UZ diode. The trigger circuit is disconnected from the sweep generator. Formation of the forward sweep begins. The sweep generator is in standby mode (switch B1-4 in the "WAITING" position). When the amplitude of the sawtooth voltage of the order of 7 V is reached, the starting circuit through the blocking circuit, the transistors T26-UZ, T27-UZ, returns to their original state. The recovery process begins, during which the time-setting capacitor C32-UZ is charged to its original potential. During recovery, the blocking circuit maintains the trigger in its original state, preventing the synchronization pulses from changing it, that is, it provides a sweep trigger delay for the time required to restore the sweep in standby mode and automatically start the sweep in a self-oscillating mode. In the self-oscillating mode, the sweep generator operates in the "AVT" position of the B1-4 switch, and the start-up and disruption of the start-up circuitry - from the blocking circuit by changing its mode.
As a sweep generator, a timing capacitor discharge circuit through a current stabilizer was selected. The amplitude of the linearly varying sawtooth voltage generated by the sweep generator is approximately 7 V. The time-setting capacitor C32-UZ during recovery is quickly charged through the T28-UZ transistor and the D12-UZ diode. During the working stroke, the D12-UZ diode is locked by the control voltage of the starting circuit, disconnecting the timing capacitor circuit from the starting circuit. The capacitor is discharged through the T29-UZ transistor, connected according to the current stabilizer circuit. The discharge rate of the timing capacitor (and, consequently, the value of the sweep factor) is determined by the magnitude of the current of the T29-UZ transistor and changes when the timing resistances R12 ... R19, R22 ... R24 are switched in the emitter circuit using switches B2-1 and B2- 2 ("TIME / DIV."). The sweep speed range has 18 fixed values. Changing the sweep factor 1000 times is provided by switching the timing capacitors C32-UZ, C35-UZ with the switch B1-5 ("mS / mS").
The sweep coefficients are adjusted with a given accuracy by the SZZ-UZ capacitor in the "mS" range, and in the "mS" range - by the R58-y3 trimming resistor, by changing the mode of the emitter follower (T24-UZ transistor) supplying the timing resistors.
The blocking circuit is an emitter detector on a T27-UZ transistor, connected according to a circuit with a common emitter, and on the R68-y3, C34-UZ elements. The input of the blocking circuit receives a sawtooth voltage from the divider R71-y3, R72-y3 at the source of the TZO-UZ transistor. During the working stroke of the sweep, the capacitance of the C34-UZ detector is charged synchronously with the sweep voltage. During the recovery of the sweep generator, the T27-UZ transistor is locked, and the time constant of the emitter circuit of the R68-y3, C34-UZ detector maintains the control circuit in its original state. The standby sweep mode is provided by blocking the emitter follower on the T26-UZ switch V1-4 ("WAITING / AVT."). In the self-oscillating mode, the emitter follower is in a linear mode of operation. The time constant of the blocking circuit is changed stepwise by the switch B2-1 and roughly B1-5. From the sweep generator, the sawtooth voltage through the source follower on the TZO-UZ transistor is fed to the sweep amplifier. The follower uses a field-effect transistor to increase the linearity of the sawtooth voltage and eliminate the influence of the input current of the sweep amplifier. The sweep amplifier amplifies the sawtooth voltage to a value that provides the specified sweep ratio. The amplifier is a two-stage, differential, cascode circuit based on transistors TZZ-UZ, T34-UZ, TZ-U2, T4-U2 with a current generator based on a transistor T35-UZ in the emitter circuit. Frequency correction of the gain is carried out by the C36-UZ capacitor. To improve the accuracy of time measurements in the KVO of the device, a sweep stretching is provided, which is provided by changing the gain of the sweep amplifier by parallel connecting the 1175-UZ, R80-UZ resistors when contacts 1 and 2 ("Stretching") of the SHZ connector are closed.
The amplified sweep voltage is removed from the collectors of the TZ-U2, T4-U2 transistors and fed to the horizontally deflecting plates of the CRT.
The change in the synchronization level is made by changing the potential of the base of the T8-US transistor by the resistor R8 ("LEVEL"), brought out to the front panel of the device.
The horizontal displacement of the beam is carried out by changing the voltage of the base of the T32-UZ transistor by the resistor R20 ("<->»), Also displayed on the front panel of the device.
The oscilloscope has the ability to supply an external synchronization signal through socket 3 ("Output X") of the SHZ connector to the T32-UZ emitter follower. In addition, an output of a sawtooth voltage of about 4 V is provided from the emitter of the TZZ-UZ transistor to socket 1 ("Output" CH ") of the SHZ connector.
The high-voltage converter (U31 unit) is designed to power the CRT with all the necessary voltages. It is assembled on transistors T1-U31, T2-U31, transformer Tpl and is powered from stabilized sources + 12V and -12V, which makes it possible to have stable supply voltages for the CRT when the supply voltage changes. The supply voltage of the CRT cathode -2000 V is removed from the secondary winding of the transformer through the doubling circuit D1-U31, D5-U31, C7-U31, S8-U31. The supply voltage of the CRT modulator is removed from the other secondary winding of the transformer also through the multiplication circuit D2-U31, DZ-U31, D4-U31, SZ-U31, S4-U31, S5-U31. To reduce the influence of the converter on the power supplies, an emitter follower TZ-U31 is used.
The CRT filament is powered from a separate winding of the Tpl transformer. The supply voltage of the first CRT anode is removed from the 1110-U31 resistor ("FOCUSING"). The brightness of the CRT beam is controlled by the Sh8-U31 resistor ("BRIGHTNESS"). Both resistors are brought out to the front panel of the oscilloscope. The supply voltage of the second anode of the CRT is removed from the Sh9-U2 resistor (brought out under the slot).
The illumination circuit in the oscilloscope is a symmetrical trigger, powered from a separate 30 V source relative to the cathode power supply -2000 V, and is made on transistors T4-U31, T6-U31. The trigger is started by a positive pulse taken from the emitter of the T23-US transistor of the trigger circuit. The initial state of the backlight trigger T4-U31 is open, T6-U31 is closed. A positive drop in the pulse from the triggering circuit transfers the backlight trigger to another state, negative - returns it to its original state. As a result, a positive pulse with an amplitude of 17 V is formed on the collector T6-U31, the duration equal to the duration of the forward sweep stroke. This positive pulse is fed to the CRT modulator to illuminate the forward sweep.
| DC ACTIVE ELEMENT MODES | |||
| Designation | Voltage, V | ||
| Collector, drain | Emitter, source | Base, shutter | |
| Amplifier U1 | |||
| T1 | 8,0-8,3 | 0,6-1 | 0 |
| T2 | -(3,8-5,0) | 1,3-1,8 | 0,6-1,2 |
| TK | -(3,8-5,0) | 1,3-1,8 | 0,6-1,2 |
| T4 | -(1,8-2,5) | -(4,5-5,5) | -(3,8-5,0) |
| T5 | -(1,8-2,5) | -(4,5-5,5) | -(3,8-5,0) |
| T6 | -(11,3-11,5) | -(1,3-1,9) | -(1,8-2,5) |
| T7 | 0,2-1,2 | -(2,6-3,4) | -(1,8-2,5) |
| T8 | 0,2-1,2 | -(2,6-3,4) | -(1,8-2,5) |
| T9 | 6,5-7,8 | 0-0,7 | 0,2-1,2 |
| T10 | 6,5-7,8 | 0-0,7 | 0,2-1,2 |
| Amplifier U2 | |||
| T1 | 60-80 | 8,3-9,0 | 8,8-9,5 |
| T2 | 60-80 | 8,3-9,0 | 8,8-9,5 |
| TK | 100-180 | 11,0-11,8 | 11,8-12,3 |
| T4 | 100-180 | 11,0-11,8 | 11,8-12,3 |
| Ultrasound scan | |||
| T1 | -(11-9) | 12 | 13,5-14,5 |
| T2 | -(11-9) | 12 | 13,5-14,5 |
| TK | -(10,5-11,5) | -(10,1-11,1) | -(11,0-10,4) |
| T4 | -(18-23) | -(8,2-10,2) | -(8,5-10,5) |
| T6 | -(14,5-17) | -(8-10,2) | -(8-10,5) |
| T7 | 6-6,5 | 0 | 0-0,2 |
| T8 | 4,5-5,5 | -(0,5-0,8) | 0 |
| T9 | 4,5-5,5 | -(0,7-0,9) | -(0,6-0,8) |
| T10 | -(11,4-11,8) | 0 | -(0,6-0,8) |
| T12 | 0,5-1,5 | -(0,6-0,8) | 0 |
| T13 | 4,5-5,5 | 3,7-4,8 | 4,5-5,6 |
| T14 | -(12,7-13) | from -0.3 to 2.0 | from -1 to 1.5 |
| T15 | 3,0-4,2 | 3,0-4,2 | 3,6-4,8 |
| T16 | -(25-15,0) | -12 | -(12,0-12,3) |
| T17 | -(25-15) | -(12,0-12,3) | -(12,6-13) |
| T18 | 4,5-5,5 | 3,0-4,1 | 2,0-2,6 |
| T19 | 7,5-8,5 | 4,5-5,5 | 5,2-6,1 |
| T20 | -12 | 5,1-6,1 | 4,5-5,5 |
| T22 | 0,4-1 | -0.2 to 0.2 | 0,5-0,8 |
| T23 | 12 | from -0.3 to 0.3 | 0,4-1 |
| T24 | -12 | -(9,6-11,3) | -(10,5-11,9) |
| T25 | 8,0-8,5 | -0.2 to 0.2 | -0.2 to 0.2 |
| T26 | -12 | -0.2 to 0.2 | 0,3-1,1 |
| T27 | -12 | 0,3-1,1 | -0.2 to 0.4 |
| T28 | 11,8-12 | 7,5-7,8 | 8,0-8,5 |
| T29 | 6,8-7,3 | -(0,5-0,8) | 0 |
| TZO | 12 | 7,3-8,3 | 6,8-7,3 |
| T32 | 12 | 6,9-8,1 | 7,5-8,8 |
| TKZ | 10,6-11,5 | 6,1-7,6 | 6,8-8,3 |
| T-34 | 10,6-11,5 | 6,1-7,4 | 6,8-8,1 |
| T35 | -(4,8-7) | -(8,5-8,9) | -(8,0-8,2) |
The voltages of the 100 V and 200 V sources are not stabilized and are removed from the secondary winding of the power transformer Tpl through the doubling circuit DS2-UZ, S26-UZ, S27-UZ. The voltages of the +12 V and -12 V sources are stabilized and are obtained from a stabilized 24 V source. The 24 V stabilizer is made on transistors T14-UZ, T16-UZ, T17-UZ. The voltage at the input of the stabilizer is removed from the secondary winding of the transformer Tpl through the diode bridge DS1-UZ. Adjustment of the stabilized voltage 24 V is made by the resistor R37-y3, brought out under the slot. To obtain +12 V and -12 V sources, an emitter follower T10-UZ is included in the circuit, the base of which is powered by a resistor R24-y3, which adjusts the +12 V source.
When carrying out repairs and subsequent tuning of the oscilloscope, first of all, it is necessary to check the modes of active elements for direct current for compliance with their values given in table. 1. If the parameter being checked does not fit within the permissible limits, it is necessary to check the serviceability of the corresponding active element, and if it is serviceable, the “strapping” elements in this cascade. When replacing an active element with a similar one, it may be necessary to adjust the operating mode of the cascade (if there is an appropriate trimmer), but in most cases this is not necessary, because the cascades are covered by negative feedback, and therefore the scatter of the parameters of the active elements does not affect the normal operation of the device.
In the event of malfunctions associated with the operation of the cathode-ray tube (poor focusing, insufficient beam brightness, etc.), it is necessary to check whether the voltages at the CRT terminals correspond to the values given in table. 2. If the measured values do not correspond to the tabulated values, it is necessary to check the serviceability of the units responsible for the generation of these voltages (high voltage source, output channels of KVO and KGO, etc.). If the voltage supplied to the CRT is within the permissible range, then the problem is in the tube itself, and it must be replaced.
Principled S1-94 oscilloscope circuit, oscilloscope block diagrams, as well as description and appearance of the measuring device, photo.
Rice. 1. External view of the S1-94 oscilloscope.
The universal service oscilloscope C1 -94 is designed to study pulse signals; in the amplitude range from 0.01 to 300 V and up to the time range from 0.1 * 10 ^ -6 to 0.5 s and sinusoidal signals with an amplitude from 5 * 10 ^ -3 to 150 V with a frequency from 5 to 107 Hz when checking industrial and household radio equipment.
The device can be used in electronic radio equipment repair services at enterprises and in everyday life, as well as by radio amateurs and in educational institutions. corresponds to the requirements of GOST 22261-82, and according to the operating conditions it corresponds to the II group of GOST 2226І — 82.
Operating conditions of the device.
a) workers:
- ambient temperature from 283 to 308 K (from 10 to 35 ° C);
- relative air humidity up to 80% at a temperature of 298 K (25 ° C);
- supply voltage (220 ± 22) V or (240 ± 24) V with a frequency of 50 or 60 Hz;
b) limiting:
- ambient temperature under extreme conditions from 223 to 323 K (from minus 50 to plus 50 ° C);
- relative air humidity up to 95% at a temperature of 298 K (25 ° C).
Electrical parameters and characteristics
- The working part of the screen is 40 X 60 mm (8X10 divisions).
- The beam line width is no more than 0.8 mm.
- The coefficient of deviation is calibrated and set in steps from 10 mV / division to 5 V / division according to the series of numbers 1,2,5.
- The error of the calibrated coefficients of deviation is no more than ± 5%, with a divider of 1:10 no more than ± 8%.
The KVO of the beam has the following parameters:
- rise time of HRP not more than 35 ns (bandwidth 0-10 MHz);
- the release at the top of the PX is not more than 10%;
- settling time of HRP is not more than 120 ns;
- irregularity of the top of the PX and the skew of the top of the PX due to uncompensation of the input dividers is not more than 3%;
- the fall of the top of the RH when the amplifier input is closed for a duration of 4 ms, no more than 10%;
- the offset of the beam due to the amplifier drift within 1 hour after a 5-minute warm-up does not exceed 0.5 division. The short-term displacement of the beam for 1 min does not exceed 0.2 divisions;
- the shift of the beam from the switching of the V / DIV switch does not exceed 0.5 division;
- periodic and random deviations of the beam from internal sources should not exceed 0.2 divisions, and from external synchronization pulses with an amplitude of 10 V not more than 0.4 divisions;
- the limits of vertical movement of the beam are not less than two values of the nominal vertical deflection. Note. When moving the image of the pulse with the knob f within the working part of the screen, distortion of the image of the pulse is permissible. The amount of pulse distortion in amplitude should not exceed 2 divisions at a minimum sweep duration of 0.1 μs.
- input impedance at direct input (1 ± 0.05) MΩ with parallel capacitance (40 ± 4) pF with 1: 1 divider - (1 ± 0.05) MΩ with parallel capacitance of about 150 pF,
- divider 1:10 - (10 ± 1) MΩ with a parallel capacitance of not more than 25 pF. The device input can be closed or open;
- the maximum amplitude of the input signal with the minimum deviation coefficient at the open input is not more than 30 V (with a divider of 1:10 - not more than 300 V);
- the permissible total value of AC and DC voltages that can be supplied when the input is closed should not exceed 250 V;
- signal delay relative to the beginning of the sweep is not less than 20 ns with internal synchronization.
The sweep can operate in both standby and self-oscillating modes and has a calibrated sweep range from 0.1 μs / div to 50 ms / div; divided into 18 fixed sub-bands according to a number of numbers 1, 2, 5.
The error of the calibrated sweep coefficients does not exceed ± 5% on all ranges, except for the sweep coefficient of 0.1 μs / division. The error of the calibrated sweep coefficient OD μs / division does not exceed ± 8%. Moving the beam horizontally sets the start and end of the sweep in the center of the screen.
The horizontal deflection amplifier has the following parameters:
- the deviation coefficient at a frequency of 10 ^ 3 Hz does not exceed 0.5 V / division;
- non-uniformity of the amplitude-frequency characteristics of the horizontal deflection amplifier in the frequency range from 20 Hz to 2 * 10 ^ 6 Hz no more than 3 dB.
The device has internal and external synchronization of the sweep.
Internal synchronization of the sweep is carried out:
- sinusoidal voltage swing from 2 to 8 divisions in the frequency range from 20 Hz to 10 * 10 ^ 6 Hz;
- sinusoidal voltage swing from 0.8 to 8 divisions in the frequency range from 50 Hz to 2 * 10 ^ 6 Hz;
- pulse signals of any polarity with a duration of 0.30 μs or more with an image size of 0.8 to 8 divisions.
External synchronization of the sweep is carried out:
- a sinusoidal signal with a swing of 1 V from peak to peak in the frequency range from 20 Hz to 10 * 10 ^ 6 Hz;
- pulse signals of any polarity with a duration of 0.3 μs and more with an amplitude of 0.5 to 3 V. Synchronization instability is not more than 20 ns.
With a reduced supply voltage and moving the handle of the pulse imaging device, an increase in the synchronization instability up to 100 ns is allowed.
When using external synchronization by pulse signals with an amplitude of 3 to 10 V, it is allowed to send an external synchronization signal to the KVO amplifier up to 0.4 divisions across the device screen with a minimum deviation coefficient.
The amplitude of the negative ramp voltage at the V socket is not less than 4.0 V. The device is powered from an alternating current network with a voltage of (220 ± 22) or (240 ± 24) V (50 or 60 Hz).
The device reaches its technical characteristics after a self-heating time of 5 minutes. The power consumed by the device from the mains at a rated voltage is not more than 32 V. A, The device provides continuous operation under operating conditions for 8 hours while maintaining its technical characteristics.
Industrial voltage, radio interference no more than 80 dB at frequencies from 0.15 to 0.5 MHz, 74 dB at frequencies from 0.5 to 2.5 MHz, 66 dB at frequencies from 2.5 to 30 MHz.
The strength of the radio interference field is not more than:
- 60 dB at frequencies from 0.15 to 0.5 MHz;
- 54 dB at frequencies from 0.5 to 2.5 MHz;
- 46 dB at frequencies from 2.5 to 300 MHz.
MTBF of the device is not less than 6000 hours.
Overall dimensions of the oscilloscope no more than 300 X 190 X X 100 mm (250X180X100 mm excluding protruding parts). The overall dimensions of the packing box when packing 4 oscilloscopes are no more than 900 X 374 X 316 mm. The overall dimensions of the box when packed by 1 oscilloscope are not more than 441 X 266 X 204 mm.
Oscilloscope mass is not more than 3.5 kg. The mass of the 1st oscilloscope in a packing box is not more than 7 kg. Weight of 4 oscilloscopes in a packing box is not more than 30 kg.
Structural scheme
Rice. 2. Block diagram of the S1-94 oscilloscope.
Design
The device is made in a desktop version of vertical construction (Fig. 3). The supporting frame is made on the basis of aluminum alloys and consists of cast front panel 7 and rear wall 20 and two stamped strips: upper 5 and lower 12. U-shaped casing and the bottom limit access to the inside of the device.
There are ventilation holes on the surface of the casing.
For the convenience of working with the device and moving it over short distances, a stand 8 is provided.
The device is made in an original frame with dimensions of 100 X 180 X 250 mm.
The oscilloscope consists of the following devices:
- housing,
- sweep,
- amplifier (90 X 120 'mm),
- amplifier (80 X 100 mm),
- power transformer.
The CRT screen and instrument controls are located on the front panel.
Rice. 3. Device design:
1 - bracket; 2 - cover; 3 - scan; 4 - screen; 5 - top bar; 6 screw; 7 - front panel; 8 - stand; 9 - front leg; 10 - amplifier; 11 - delay line; 12 - bottom bar; 13 - back leg; 14 - power cord; 15 - power transformer; 16 - amplifier; 17 - CRT panel; 18 - screw; 19 - cover; 20 - back wall.
Voltage tables
Checking the modes given in table. 1 (unless otherwise specified) is made relative to the device body under the following conditions:
- amplifiers U1 and U2: produced with a balanced amplifier; the UZ-V1-4 switch is set to the WAITING position; with resistors R2 and R20, the beam is installed in the center of the screen;
- ultrasound sweep: with a resistor R8 (LEVEL), the base potential of the UZ-T8 transistor is set to O; switches UZ-V1-2, UZ-V1-Z, UZ-V1-4 are set to the positions INUTR, JL, WAITING, respectively, with the resistor R20 the beam is set in the center of the screen; switches V / DIV and TIME / DIV are in positions "05" and "2", respectively; the voltage at the electrodes of the UZ-T7 transistor is removed in the position * of the V / DIV switch; the voltage ua of the electrodes of the UZ-T4, UZ-T6 transistors are checked against the common point of the UZ-D2 and UZ-D3 diodes, while the UZ-V1-4 switch is set to the AVT position; supply voltages 12 and minus 12 V must be set with an accuracy of ± 0.1 V, with a mains voltage of 220 ± 4 V.
Table 1.
Table 2.
Checking the modes shown in Table 2 (except for those specifically mentioned) is carried out with respect to the device body. Checking the mode on contacts 1, 14 of the CRT (L2) is carried out, relative to the potential of the cathode (minus 2000 V). The modes of operation may differ from those indicated in the table. 1, 2 by ± 20%.
Coil and transformer winding data
Transformer winding data Tr1 (ШЛ х 25).
Data of the winding of the UZ-Tr1 transformer.
Component location
Rice. 1. Layout of elements on the PU amplifier U1.
Rice. 2. Layout of elements on the PU (amplifier U2).
Layout plan of elements on the PU - sweep U3.
Layout of items on the rear of the oscilloscope.
Layout plan for the front panel of the oscilloscope.
Schematic diagram
S1-94 oscilloscope electrical schematic diagram. S1-94 oscilloscope amplifier and high-voltage power supply.
If you have an S1-94 oscilloscope at your disposal, its capabilities can be significantly expanded with the help of the proposed attachments.
Active probe.
The input capacitance of a C1-94 oscilloscope with a 1: 1 divider is significant (150 pF) for high frequencies, so the oscilloscope's input impedance at these frequencies is often too low. The active probe developed by I. Nechaev from Kursk will help to improve this indicator.
A schematic of the active probe is shown in Fig. 78. Its input stage is made on a field-effect transistor (VT1) with an insulated gate. To protect the transistor from overloads by the input voltage, diodes VD1 and VD2 are installed in the gate circuit.
From the drain of the field-effect transistor, the signal investigated by the probe is fed to the output stage, assembled on a bipolar transistor VT2. This stage uses negative voltage feedback through the resistor R4 and the capacitor C4, due to which the probe has a low output impedance, a wide bandwidth and works well for cables up to 1.5 m long.
The transfer coefficient of the probe reaches 1, the input capacitance is 5 ... 6 pF, the input resistance is 250 kOhm, the bandwidth (at a level of 3 dB) is 0.01 ... 10 MHz. A signal with an amplitude of no more than 3 V can be applied to the probe input.
For the probe, transistors KP301B-KP301G, KP304 (VT1), KT315A-KT315G, KT316, KT342 with any letter index (VT2) are suitable. Diodes can be any low-power silicon with minimum capacitance and reverse current.
The design of the stylus depends on the parts used. For example, the author placed parts on a 55X15 mm PCB made of fiberglass and placed the board in an aluminum cup from under validol. The probe is connected to the oscilloscope with any high-frequency shielded cable, preferably a small diameter.
When adjusting the probe, first select (if necessary) the resistor R1 in order to ensure the operating mode of the transistor VT2 indicated in the diagram. The transmission coefficient is set by the selection of the resistor R4, and the upper limit of the bandwidth - by the selection of the capacitor C4. The lower limit of the passband depends on the capacitance of the capacitor C1.
It is advisable to check the amplitude-frequency response of the probe. If a rise in frequencies corresponding to the upper limit of the passband is detected on it, it will be necessary to connect a 30 ... 60 Ohm resistor in series with the capacitor C4.
Two-channel electronic switch. 
It was also developed by I. Nechaev. The switch (Fig. 79) consists of two electronic keys made on transistors VT1, VT2 and a control device, which uses transistors VT2, VT3 and microcircuits DM, DD2. The signals under investigation are fed through capacitors C1 and C2 to variable resistors R1 and R2 for channel gain control. Signals from the resistor engines are sent to electronic keys. If a logic level 1 (> 4 V) is applied to the gate of the field-effect transistor, the resistance of its channel will be large (> 1 MΩ) and the input signal will not go to the output of the switch. If there is a voltage at the gate that corresponds to a logic 0 level, the channel resistance will not exceed 1 kΩ and the input signal will pass to the switch output practically without attenuation. The control voltages to the gates of the key transistors are supplied from the direct and inverse outputs of the DD2.1 trigger, therefore, one or the other signal under investigation will be sent to the oscilloscope input. The switch operates in two modes "Alternately" and "Simultaneously" set by switch SA1. Let's consider them in more detail.
In the "Alternate" mode, when the switch contacts are in the position shown in the diagram, the switching frequency is determined by the duration of the oscilloscope sweep. It happens like this. The sawtooth voltage from pin 1 of the SHZ connector (see the diagram of the S1-94 oscilloscope) goes to the XS3 socket of the switch and then to the pulse shaper assembled on VT3 VT4 transistors and logic element DD1.3. The shaper generates pulses of positive polarity that coincide in time and duration with the reverse sweep pulses. These pulses through the contacts of the SA1 switch are fed to the trigger input DD2.1 and transfer it (and hence the keys) each time to a new state. Thus, the signals under investigation arrive at the output of the device in turn.
Since switching occurs during the return path of the beam, the moments of switching the switch on the oscilloscope screen are not visible and a complete illusion of working with a "two-beam" oscilloscope is created. This mode is most convenient, since the switching frequency is synchronized with the sweep frequency, which, in turn, is synchronized by the signal under investigation. In this mode, the switch allows observing signals with a frequency of up to 300 kHz on the screen.
In the "Simultaneous" mode, pulses from the generator collected on the elements DD1.1 and DD1.2 are received at the trigger input. In this case, the switching frequency is half the pulse repetition rate of the generator and is equal to 40 ... 50 kHz, the signals under investigation are observed on the screen simultaneously, and the electron beam is not extinguished at the moments of switching the switch. This mode is not very convenient, so it is advisable to use it when examining signals with a frequency of several tens of hertz.
The relative position of the signal oscillograms is set with the variable resistor R7, and the amplitude of the signals - with the variable resistors R1 and R2.
In the switch, you can use transistors KT315, KT301, KT316 with any letter indices (VT3, VT4), KP103I - KP103L with a cut-off voltage of the drain current of not more than 2.5 V (VT1, VT2). Diode VD1 - any of the series D2, D9. Coil L1 is made on a ring of standard size К7Х4х1.5 made of ferrite 2000NM, it contains 50 ... 60 turns of wire PEV-2 0.12. Switch SA1 - MT-1 or other small-sized.
Establishing a switch is mainly reduced to the selection of a capacitor C4 to ensure stable operation of the pulse shaper and trigger at various sweep durations. The switching frequency in the "Simultaneous" mode can be changed by selecting the capacitor C3 or by changing the inductance of the coil L1.
Capacitance meter. 
When you need to measure the capacitance of a capacitor or select two identical capacitors in terms of capacitance, this can be done indirectly - by the duration of charging the tested capacitor through a constant resistor between two high-precision voltage levels. Under these conditions, the charging time is strictly proportional to the capacity. The sweep of the C1-94 oscilloscope, which has sufficient linearity and stability, allows it to be used for measuring time intervals.
Moskvich I. Borovik developed on the basis of the mentioned principle an attachment (Fig. 80) for measuring the capacitance of polar and non-polar capacitors from 500 pF to 50,000 μF with an error of ± 5 ... 7%. The tested capacitor is under voltage close to ± 1.3 V, the AC voltage swing on it does not exceed 40 MB. Power to the console comes from the oscilloscope's power supply, for which suitable contacts are inserted into the input connector Ш1 into empty slots 4 and 5 and connect them to contacts 8, 9 of the U1 board. It is not excluded, of course, the option of powering the set-top box from an autonomous source.
The attachment is a multivibrator on a DA1 microcircuit with an output current amplifier — a complementary emitter follower on transistors VT1, VT2. Connecting the tested capacitor to terminals XT1, XT2 causes autogeneration. The duration of the output pulse is directly proportional to the capacitance of this capacitor. The elements of the attachment are selected so that a pulse duration of 10 μs corresponds to a capacitance of 1 μF (or 1000 pF in another sub-range set by the SB1 switch). The pulse swing at the output of the set-top box is about 10 V. The oscilloscope operates in standby mode with an internal trigger on the signal edge.
Key tags: B.S. Ivanov. Oscilloscope attachments
This article is intended for specialists who need to repair and adjust the S1-94 oscilloscope. The oscilloscope has a structural diagram typical for devices of this class. It contains a vertical deflection channel (KVO), a horizontal deflection channel (KGO), a calibrator, an electron-beam indicator with a high-voltage power supply and a low-voltage power supply.
The simplified block diagram does not show only two power supply units of a high-voltage source that generates high voltage for a cathode-ray tube (CRT) and a low-voltage one for the operation of all other nodes, and there is also no built-in calibrator for setting up the oscilloscope before taking measurements.
The signal under investigation is fed to the “Y” input of the vertical deflection channel and then follows to the attenuator, which is nothing more than a multi-position switch that adjusts the sensitivity threshold. Its scale is calibrated in Volt / cm or Volt / div. This refers to one division of the graticule on the CRT display. There are also marked values: 0.1 V, 10 V, 100 V. If we do not know the approximate amplitude of the signal under investigation, then we set the minimum sensitivity, 100 volts per division.
The oscilloscope kit includes 1: 10 and 1: 100 dividers, which are cylindrical and rectangular nozzles with connectors. They are used for the same purpose as an attenuator, and in the case of measurements with short pulses, they compensate for the capacitance of the coaxial cable. The figure below shows an external divider for the S1-94 oscilloscope. Its, the division ratio is 1 to 10.
Thanks to this attachment, you can significantly expand the capabilities of the device, since when using it, you can investigate signals with a much higher amplitude of hundreds of volts. From the output of the divider, the signal goes to the preamplifier. It then forks and goes to the delay line and timing switch. The delay line is necessary to compensate for the response time of the horizontal scan generator with the arrival of the measured signal to the vertical deflection amplifier. The final amplifier is designed to form the voltage going to the "Y" plate and sets the deflection of the vertical beam.
The sweep generator is required to generate the sawtooth voltage, which follows the horizontal deflection amplifier and the “X” plates and provides horizontal deflection of the beam. It is equipped with a time per division ("Time / div") graduated switch and a sweep time scale.
The sync device starts the sweep generator in parallel with the appearance of the signal at the start point of the display. As a result, on it we see the image of the pulse unfolded in time. The synchronization switch is equipped with the following ranges: Synchronization from the signal under investigation; Synchronization from the network; Synchronization from an external source. In amateur radio practice, the first band is most often used
The KGO includes a sync amplifier, a sync trigger, a trigger circuit, a sweep generator, a blocking circuit, and a sweep amplifier. It is designed to provide a linear deflection of the beam with a given sweep ratio from 0.1 μs / div to 50 ms / div with a step of 1-2-5.
The calibrator generates a signal to calibrate the instrument in amplitude and time. The cathode ray indicator assembly consists of a cathode ray tube (CRT), a CRT power supply circuit, and an illumination circuit. The low-voltage power supply is designed to power all functional devices with voltages of +24 V and ± 12 V. Consider the operation of an oscilloscope at the level of a circuit diagram. The signal under investigation through the input connector Ш1 and the button switch В1-1 ("Open / Closed input") is fed to the input switchable divider on the elements R3 ... R6, R11, C2, C4 ... C8. The input divider circuit provides a constant input impedance regardless of the position of the vertical sensitivity switch B1 ("V / DIV"). The divider capacitors provide frequency compensation for the divider across the entire frequency band.
From the output of the divider, the signal under investigation is fed to the input of the KVO preamplifier (block U1). A source follower for an alternating input signal is assembled at T1-U1. In direct current, this stage ensures symmetry of the operating mode for the subsequent amplifier stages. The divider on the resistors R1-y1, R5-y1 provides an input impedance of the amplifier equal to 1MΩ. D1-U1 diode and D2-U1 zener diode provide input protection against overloads.
The two-stage preamplifier is made on transistors T2-U1 ... T5-U1 with general negative feedback (OOS) through R19-y1, R20-y1, R2-y1, R3-y1, C2-U1, R1, C1, which allows to obtain an amplifier with the required bandwidth, which practically does not change with a stepwise change in the gain of the stage by two and five times.
The change in the gain is carried out by changing the resistance between the emitters of the transistors VT2-y1, VT3-U1 by switching resistors R3-y1, R16-y1 and R1 in parallel with the resistor R16-y1. The amplifier is balanced by changing the base potential of the T3-U1 transistor with a resistor R9-y1, which is brought out under the slot. The vertical displacement of the beam is made by the resistor R2 ("Z") by changing the base potentials of the transistors T4-U1, T5-U1 in antiphase.
Such inclusion of the delay line ensures its matching with the stages of the preliminary and final amplifiers. Frequency gain correction is performed by the R35-y1, C9-y1 chain, and in the power amplifier stage - by the C11-y1, R46-y 1, C12-y1 chain. Correction of the calibrated values of the coefficient of deviation during operation and change of the CRT is carried out by the resistor R39-y1, brought out under the slot. The final amplifier is assembled on transistors T1-U2, T2-U2 according to a scheme with a common base with a resistive load Ш1-У2 ... R14-y2, which makes it possible to achieve the required bandwidth of the entire vertical deflection channel.
From the collector loads, the signal goes to the vertical deflection plates of the CRT. The signal under study from the KVO preamplifier circuit through the emitter follower stage on the T6-U1 transistor and the B1.2 switch is also fed to the input of the KGO synchronization amplifier for synchronous triggering of the sweep circuit. The synchronization channel (block U3) is designed to start the sweep generator synchronously with the input signal to obtain a still image on the CRT screen. The channel consists of an input emitter follower on the T8-U3 transistor, a differential amplification stage on the T9-U3, T12-U3 transistors and a synchronization trigger on the T15-U3, T18-U3 transistors, which is an asymmetric trigger with emitter coupling with an emitter follower on input on the transistor T13-U2. The D6-U3 diode is included in the base circuit of the T8-U3 transistor, which protects the synchronization circuit from overloads. From the emitter follower, the clock signal is fed to the differential amplification stage.
The differential stage switches (V 1-3) the polarity of the synchronizing signal and amplifies it to a value sufficient for triggering the synchronization trigger. From the output of the differential amplifier, the sync signal is fed through the emitter follower to the input of the synchronization trigger. A signal normalized in amplitude and shape is removed from the collector of the T18-U3 transistor, which, through the decoupling emitter follower on the T20-U3 transistor and the C28-U3, R56-Y3 differentiating chain, controls the operation of the trigger circuit. To increase the stability of synchronization, the synchronization amplifier, together with the synchronization trigger, is powered from a separate 5 V voltage regulator on the T19-U3 transistor. The differentiated signal is fed to the trigger circuit, which, together with the sweep generator and the blocking circuit, provides the formation of a linearly varying sawtooth voltage in the standby and self-oscillating modes.
The triggering circuit is an unbalanced emitter-coupled flip-flop on transistors T22-y3, T23-y3, T25-y3 with an emitter follower at the input on transistor T23-y3. The initial state of the trigger circuit: T22-y3 is on, T25-y3 is on. The potential to which the capacitor C32-U3 is charged is determined by the collector potential of the T25-y3 transistor and is approximately 8 V. The D12-U3 diode is open. With the arrival of a negative pulse at the base of T22-y3, the trigger circuit is inverted, and a negative drop on the collector T25-y3 blocks the diode D12-U3. The trigger circuit is disconnected from the sweep generator. Formation of the forward sweep begins.
The sweep generator is in standby mode (switch B1-4 in the "WAITING" position). When the amplitude of the sawtooth voltage of the order of 7 V is reached, the starting circuit through the blocking circuit, the transistors T26-U3, T27-y3 returns to their original state. The recovery process begins, during which the timing capacitor C32-U3 is charged to its original potential. During recovery, the blocking circuit maintains the trigger in its original state, preventing the synchronization pulses from changing it, that is, it provides a sweep trigger delay for the time required to restore the sweep in standby mode and automatically start the sweep in a self-oscillating mode.
In the self-oscillating mode, the sweep generator operates in the "AVT" position of the B1-4 switch, and the start-up and disruption of the start-up circuitry - from the blocking circuit by changing its mode. As a sweep generator, a timing capacitor discharge circuit through a current stabilizer was selected. The amplitude of the linearly varying sawtooth voltage generated by the sweep generator is approximately 7 V. The timing capacitor C32-U3 during recovery is rapidly charged through the transistor T28-U3 and the diode D12-U3. During the working stroke, the diode D12-U3 is locked by the control voltage of the starting circuit, disconnecting the timing capacitor circuit from the starting circuit. The capacitor is discharged through the T29-U3 transistor, connected according to the current stabilizer circuit. The discharge rate of the timing capacitor (and, consequently, the value of the sweep factor) is determined by the magnitude of the current of the transistor T29-U3 and changes when switching timing resistances R12 ... R19, R22 ... R24 in the emitter circuit using switches B2-1 and B2- 2 ("TIME / DIV."). The sweep speed range has 18 fixed values.
Changing the sweep factor 1000 times is provided by switching the timing capacitors C32-U3, C35-U3 with the switch B1-5 ("mS / mS"). The sweep coefficients are adjusted with a given accuracy by the capacitor C33-U3 in the "mS" range, and in the "mS" range - by the R58-y3 trimming resistor, by changing the mode of the emitter follower (transistor T24-U3) supplying the timing resistors. The blocking circuit is an emitter detector on a T27-U3 transistor, connected according to a circuit with a common emitter, and on the elements R68-y3, C34-U3.
The input of the blocking circuit receives a sawtooth voltage from the divider R71-y3, R72-y3 at the source of the transistor T30-U3. During the working stroke of the sweep, the capacitance of the C34-U3 detector is charged synchronously with the sweep voltage. During the recovery of the sweep generator, the transistor T27-U3 is locked, and the time constant of the emitter circuit of the detector R68-y3, C34-U3 maintains the control circuit in its original state. The standby sweep mode is provided by blocking the emitter follower on the T26-U3 with the V1-4 switch ("WAITING / AVT."). In the self-oscillating mode, the emitter follower is in a linear mode of operation. The time constant of the blocking circuit is changed stepwise by the switch B2-1 and roughly B1-5.
From the sweep generator, the sawtooth voltage through the source follower on the T30-U3 transistor is fed to the sweep amplifier. The follower uses a field-effect transistor to increase the linearity of the sawtooth voltage and eliminate the influence of the input current of the sweep amplifier. The sweep amplifier amplifies the sawtooth voltage to a value that provides the specified sweep ratio. The amplifier is a two-stage, differential, cascode circuit based on transistors T33-U3, T34-U3, T3-U2, T4-U2 with a current generator on a transistor T35-U3 in the emitter circuit. Frequency correction of the gain is carried out by the capacitor C36-U3. To improve the accuracy of time measurements in the KVO of the device, a sweep stretching is provided, which is provided by changing the gain of the sweep amplifier by parallel connecting the resistors R75-Y3, R80-U3 when contacts 1 and 2 ("Stretching") of the Ш3 connector are closed.
The amplified sweep voltage is removed from the collectors of the transistors T3-U2, T4-U2 and fed to the horizontally deflecting plates of the CRT.
The synchronization level is changed by changing the potential of the base of the T8-U3 transistor by the resistor R8 ("LEVEL") brought out to the front panel of the device.
The horizontal displacement of the beam is carried out by changing the voltage of the base of the transistor T32-U3 by the resistor R20 ("^"), which is also displayed on the front panel of the device.
The oscilloscope has the ability to supply an external synchronization signal through socket 3 ("Output X") of the Ш3 connector to the T32-U3 emitter follower. In addition, there is a sawtooth voltage output of the order of 4 V from the emitter of the T33-U3 transistor to socket 1 ("Output N") of the Ш3 connector.
The high-voltage converter (U31 unit) is designed to power the CRT with all the necessary voltages. It is assembled on transistors T1-U31, T2-U31, transformer Tr1 and is powered from stabilized sources + 12V and -12V, which makes it possible to have stable supply voltages for the CRT when the supply voltage changes. The supply voltage of the CRT cathode -2000 V is removed from the secondary winding of the transformer through the doubling circuit D1-U31, D5-U31, C7-U31, S8-U31. The supply voltage of the CRT modulator is removed from the other secondary winding of the transformer also through the multiplication circuit D2-U31, D3-U31, D4-U31, C3-U31, C4-U31, C5-U31. To reduce the influence of the converter on the power supplies, an emitter follower T3-U31 is used.
The CRT filament is powered from a separate winding of the Tr1 transformer. The supply voltage of the first CRT anode is removed from the resistor R10-y31 ("FOCUS"). The brightness of the CRT beam is controlled by the resistor R18 ^ 31 ("BRIGHTNESS"). Both resistors are brought out to the front panel of the oscilloscope. The supply voltage of the second anode of the CRT is removed from the resistor R19-U2 (brought out under the slot).
The illumination circuit in the oscilloscope is a symmetrical trigger, powered from a separate 30 V source relative to the cathode power supply -2000 V, and is made on transistors T4-U31, T6-U31. The trigger is triggered by a positive pulse taken from the emitter of the T23-U3 transistor of the trigger circuit. The initial state of the backlight trigger T4-U31 is open, T6-U31 is closed. A positive drop in the pulse from the triggering circuit transfers the backlight trigger to another state, negative - returns it to its original state. As a result, a positive pulse with an amplitude of 17 V is formed on the collector T6-U31, the duration equal to the duration of the forward sweep stroke. This positive pulse is fed to the CRT modulator to illuminate the forward sweep.
The oscilloscope has a simple amplitude and time calibrator, which is made on the T7-U3 transistor and is an amplifier circuit in the limiting mode. A sinusoidal signal with the frequency of the mains supply is fed to the input of the circuit. From the collector of the transistor T7-U3, rectangular pulses are removed with the same frequency and amplitude of 11.4 ___ 11.8 V, which are fed to the input divider KVO in position 3 ("") of switch B1. In this case, the sensitivity of the oscilloscope is set to 2 V / div, and the calibration pulses should occupy five divisions of the vertical scale of the oscilloscope. The sweep factor is calibrated in position 2 of switch B2 and position "mS" of switch B1-5.
The voltages of the 100 V and 200 V sources are not stabilized and are removed from the secondary winding of the power transformer Tr1 through the doubling circuit DS2-U3, C26-U3, C27-U3. The voltages of the + 12V and -12V sources are stabilized and obtained from a stabilized 24V source. The 24V stabilizer is made on transistors T14-U3, T16-U3, T17-U3. The voltage at the input of the stabilizer is removed from the secondary winding of the transformer Tr1 through the diode bridge DS1-U3. Adjustment of the stabilized voltage 24 V is performed by a Sh7-U3 resistor brought out under the slot. To obtain +12 V and -12 V sources, an emitter follower T10-U3 is included in the circuit, the base of which is powered by a resistor R24-Y3, which adjusts the +12 V source.
When carrying out repairs and subsequent tuning of the oscilloscope, first of all, it is necessary to check the modes of active elements for direct current for compliance with their values given in table. 1. If the parameter being checked does not fit within the permissible limits, it is necessary to check the serviceability of the corresponding active element, and if it is serviceable, the “strapping” elements in this cascade. When replacing an active element with a similar one, it may be necessary to adjust the operating mode of the cascade (if there is an appropriate trimmer), but in most cases this is not necessary, because the cascades are covered by negative feedback, and therefore the scatter of the parameters of the active elements does not affect the normal operation of the device.
In the event of malfunctions associated with the operation of the cathode-ray tube (poor focusing, insufficient beam brightness, etc.), it is necessary to check whether the voltages at the CRT terminals correspond to the values given in table. 2. If the measured values do not correspond to the tabulated values, it is necessary to check the serviceability of the units responsible for the generation of these voltages (high voltage source, output channels of KVO and KGO, etc.). If the voltage supplied to the CRT is within the permissible range, then the problem is in the tube itself, and it must be replaced.
