Device for testing lamps diagram. Vacuum tube testing

In Fig. I shows a diagram of a radio tube tester, with which you can test over 70 types of receiving and amplifying tubes.

Using this tester, you can check the integrity of the filament, the anode current of the lamp in a given operating mode, determine a short circuit between the electrodes and the presence of a break between the electrodes and the pins of the base.

The Tpi power transformer allows you to obtain different voltages (1.2; 2; 4; 5; 6.3 and 12 V) to power the filament of the lamps under test. The voltage of 60 V is removed from the same transformer (winding II); which is used to check the integrity of the filament of lamps. The required filament voltage is set by switch P\.

The device has a total of eight lamp panels: three with an octal base (for lamps in which the filament is supplied to the legs 2-7, 2-8 and 7-S), two for seven-pin lamps of the finger series (in which the filament is brought to the legs 3-4 and 1-7) and three for nine-pin lamps of the finger series (the filament is routed to pins 1-6, 1-9, 4-5). Each of the panels on the front side of the device is marked with a corresponding number, indicating the numbers of the contact petals to which the filament voltage is supplied, and the type 1 of the base.

As can be seen from the schematic diagram of the device, the switching of the lamp electrodes is carried out by changeover switches (toggle switches) Bkj-Vkyu, which allow connecting any electrode or group of electrodes to a common negative or test voltage, which is removed from the capacitive filter (C,) connected at the output of the rectifier.

For ease of use of the device, the terminals from the switch engines Vk, -Vk 9 are connected to the corresponding contact petals of the lamp panels. The numbering of the panel petals is the same as in the lamp pinouts given in various reference books on electric vacuum devices. The lamp incandescence U n is connected directly to the petals of the lamp panels according to the pinout. These petals are not connected to the VK x -VK switches. For lamps in which the terminal of one of the electrodes is located at the top of the cylinder, a special terminal B and switch Vk No. are provided. This terminal is connected to the circuit with a special plug.

In Fig. 2, bottom left, as an example, there are diagrams for connecting the legs of panels of finger-type lamps, in which the filament is routed to legs 3-4 (base No. 1), 4-5 (base No. 2) and 1-9 (base No. 3).

When operating the device, in order to reduce possible erroneous switching on, a special table should be drawn up, which indicates the type of lamp being tested, the base, the numbers of the lamp electrode leads to the toggle switches VK ( -VK 3 and the position of the handle of the universal shunt. The note indicates the numbers of the legs to which the conclusions are made from electrodes of the same type (in the numerator), and the name of these electrodes (in the denominator). A sample of such a table for several types of lamps is shown in Fig. 1.

Before measuring the total anode current, the lamp is checked for the integrity of the filament and the absence of a short circuit between the electrodes.

To check the integrity of the filament, switch I is set to the zero position, thereby turning off the power to the filament. The lamp to be tested is then switched on to the appropriate lamp panel. If the filament is not broken, the neon lamp L\ will light up. If the filament breaks, the neon lamp will not light -

To test a lamp (for example 6Zh1P) for a short circuit between the electrodes, the toggle switches Vk\, Vk g, Vk$-Vk 7, to which the lamp electrodes are connected (see table), are set to position 1. In this case, all the lamp electrodes are connected to each other and join the general minus. The plus of the rectifier through resistances Rs, Ri, milliammeter ША with a universal shunt, contacts 3-4 of the KN button is connected to contacts of 2 toggle switches VK\-V/s 10. If now each of the toggle switches Vk\, Vk$, Vk 6 or Vk g, Vk 7 (simultaneously) is switched to position 2 (and then to the original position), then the milliammeter needle wA will deflect only in the event of a short circuit between the electrode under study and some or another electrode in the lamp. By placing the toggle switch (or toggle switches Vk g, Vk 7), at which the milliammeter needle deviated, to position 2 and continuing to move the remaining toggle switches in turn to position 2 and back, you can determine from the reading of the milliammeter needle which electrodes there is a short circuit.

Lamps are tested for short circuits without turning on the filament voltage, i.e., with the switch /7 b in the zero position

When testing a lamp for a break between the electrodes and the output pins, a normal voltage is applied to the filament (in our case, 6.3 V). This is achieved by setting the /7] switch to the appropriate position.

Next, all the electrodes of the lamp with toggle switches Vk ъ Vk g, Vk 5, Vk e, Vk 7 are connected to the negative pole of the anode voltage (position I). When alternately switching (to position 2 and back) the toggle switches Vk and Vk$, Vk e, to which for a given type of lamp the grid electrodes and the anode of the lamp are connected (see table), a circuit is formed for measuring the current in the circuit of individual electrodes: plus the anode voltage-resistance Rs, Ri-milliammeter ta-contacts 3-4 buttons Kn - contacts 2-3 of one of the toggle switches Vk\, Vk$, Vk in - the lamp electrode under test - cathode - common minus.

In this circuit, the HpA milliammeter will show an increase in current only if there is no break in the circuit of the electrode under test.

When testing the lamp by anode current, the cathode of the lamp through contacts 1-3 of toggle switches Vk 2, Vk 7 remains connected to the common minus, all other electrodes with toggle switches Vk\, Bks, Vk e are connected to the positive of the anode voltage. The universal shunt is installed in the position indicated in the table. By pressing the Kn button on the device scale, the suitability of the lamp is determined by the emission current. The electrical circuit that is formed in this case differs from the previous one in that contacts 1-2 of the Kn button close one of the limiting resistances, and contacts 4-5 of the same button turn on a universal shunt with a maximum measurement limit of 50 mA and a minimum of about 1 mA.

The use of this method of measuring the anode current, which characterizes the emissivity of the cathode, made it possible to create an easily readable lamp suitability scale: a deviation of the milliammeter needle by less than eight scale divisions (the instrument scale has twenty divisions in total) indicates the unsuitability of the lamp, more than ten indicates their suitability. The first eight divisions are colored red, the last ten - green. The scale area between eight and ten divisions is colored yellow. The presence of the milliammeter needle in this zone indicates a reduced emissivity of the cathode of the lamp under test.

The lamp tester is mounted on a duralumin panel and enclosed in a wooden box covered with leatherette measuring 150X250X270 mm.

Power transformer 7p, made on a core made of Sh-20 plates, set thickness 60 mm. Winding I contains 550+85+465 turns of 0.35 PE wire, winding II - 275 turns of 0.12 PE wire, winding III - 60 turns with taps from 6, 10, 20, 25 and 38 turns, and up to the 35th turn, the winding is made with PE 1.2 wire, and then with PE 0.8 wire.

To work with the device, as indicated above, it is necessary to draw up a table indicating the position of the universal shunt, which is determined when testing known-good lamps. When calibrating the device, the correct position of the universal shunt handle is determined by the reading of the milliammeter needle, which should deviate by 12-15° of the scale. Switching the toggle switches to which the electrodes of the same name are connected must be done simultaneously, setting them, depending on the type of measurement, to position 1 or 2. Failure to follow this rule may lead to an erroneous conclusion about the presence of a short circuit in the lamp or its serviceability.

When testing combination lamps, each part of the lamp is checked separately.

Once upon a time, during the golden era of tube technology, receiving and amplifying radio tubes were used in military, metrological, navigation, and industrial equipment. Therefore, the quality in the production of radio tubes was brought to the appropriate level. Then the imperative of the equipment designer was to obtain the specified characteristics without selecting lamps and reducing the number of lamp parameters used in the design.

This approach will not work today. By definition, new-made lamps do not require serious use (but the fetishization of lamps is thriving), with all the ensuing consequences. Well, who takes a guitar amp seriously except the user and his quarrelsome neighbors? Few people check even the basic compliance of the output power (and it depends on the selection of lamps) with the rated value during equipment maintenance!

On the other hand, those original lamps (NOS - New Old Stock, which means “from old stocks”), which today can be obtained by hook or by crook, were not necessarily stored in the Pentagon warehouses (where the lamps had priorities far from sound), but could remain as unclaimed rejection or something like that. Who knows?

Thus, on the one hand, we have lamps whose characteristics have a significant scatter, and on the other hand, there is subjectivity, “taste” in assessing the performance of the equipment (aka sound equipment). It is not possible to eliminate the last extra “degree of freedom”.

This means that lamps must be carefully checked and selected. Not writing on the lamp packaging one single, hastily taken, value of the anode current in who knows what mode - this is not selection! And give an adequate set of parameters. In fact, this is exactly what decent sellers do. Why are we any worse?

It would seem that lamp meter devices like the domestic L3-3 (and less accessible American ones, Hickok) exist and are quite accessible. These instruments allow you to perform a wide range of tests on hundreds of lamp types.

They also have their own limitations that do not allow us to solve all our problems. So, for example, it is impossible to “fry” a lamp of type 6550 on L3-3. And the excellent emission indicators of some small lamp, recorded using such devices, indicate the performance of the lamp, with which consumer equipment will be unsuitable for use due to the microphone effect or noise. Add to this the “delights” of reading on a multifunctional dial indicator scale. We are interested in specific, application-related tests of lamps of a limited range and in large quantities.

Test bench developed by Yuri Bolotov

Therefore, it is advisable to test lamps for sound equipment using specialized means that you have to make yourself.

I would like to note in this matter the importance of stabilizing supply voltages in equipment, be it filament, bias or high voltages.

Preamp tube testing

Most of the lamps used in audio equipment are double triodes with identical halves, in a finger design. Exceptions are rare and exotic and require individual consideration. This is where the specificity of mass testing of lamps for commercial purposes comes from.

In addition to rejecting unsuitable specimens, there is the task of identifying specimens with special properties:

Instances with a higher or lower gain (for example, high gain);
- low noise and non-microphone (V1, low noise);
- with identical gains of triodes in the cylinder (balanced).

The remaining specimens, not outstanding in terms of the listed properties, but undoubtedly suitable, form the corresponding group of lamps (without additional designations, standard, regular - I prefer the latter designation).

In principle, the static mode of triodes is of little concern to us (except for rare special cases), it is important that it more or less fits into the standards for lamps of this type and that the “swing” of the halves is within certain limits.

The test bench allows you to implement typical electrical modes most often found in audio equipment and conduct specialized tests for the range of lamp types of interest.

The lamp is installed on a stand, high voltage is supplied after the cathode is warmed up. Then the lamp is trained for some time (from 20 minutes), the voltage at the anodes is controlled. An alternating voltage from a generator is supplied to the input of the stand, and the voltage amplified by each triode is measured. Based on the result, one can judge the amplification capabilities of the lamp.

The insulation between the cathode and the heater is also tested, for which it is possible to introduce a constant voltage between the filament and the common wire of the circuit. A negative voltage is applied to this section within the limits of 100 V acceptable for most lamps. We judge the quality of the insulation by the amount of current flowing in this circuit (it is negligible). In general, lamps for serious use are subject to a more severe voltage test of about 250 V, which can also be achieved if you are willing to pay extra.

The next stage of the test is subjective. The stand with the test tube is located approximately 1 foot in front of a guitar cabinet with a twelve-inch speaker connected to a high-gain guitar amplifier, configured so that the guitar produces a clear “j-j” and the volume at this point in space is about 110 dB. The outputs of the stand, of which there are two, as well as the triodes in the cylinder of the lamp under test, are connected in turn to the input of the guitar amplifier.

The lamp, which is prone to microphone effects, instantly reveals itself with a loud and joyful pig squeal. Additionally, by tapping a seemingly non-microphone lamp with a wooden stick, we find out the degree of its resistance to this evil. Well, the noises... you can hear them! Character, coloring, level - it is quite difficult to adequately measure. But some experience as a user of high-gain guitar amplifiers allows you to get an assessment in exactly the form that is required - in an emotional way, because this is what the meaning of using tubes ultimately comes down to.

Output tube test

Let's assume that the lamp is a pentode or beam tetrode; these are the lamps that are used in the output stages of the vast majority of tube amplifiers.

Testing the lamp begins by applying voltages to the electrodes in the proper order. At first, the lamp operates in light mode. If there are no signs of obvious unsuitability of this instance, we move on to the next stage.

Anode current;
- current of the second grid;
- current of the first grid;

An alternating voltage from the generator is introduced into the first grid circuit. The alternating component of the anode current is measured. From this value the slope is calculated using the first grid.

An alternating voltage is introduced into the circuit of the second grid, and the alternating component of the anode current is measured. From this value the slope is calculated using the second grid.

Then the installation is switched back to light mode. Anode current at reduced power dissipated by the anode (approximately 20% of maximum). This additional control point is of some importance for the selection of pairs of lamps that will operate in push-pull cascades of class AB or B.

Thus, we obtain a set of parameters sufficient to group lamps into pairs or quads. The basis for rejecting a lamp may be “outstanding” values ​​of these parameters, especially an abnormally large value of the first grid current. The latter indicates, for a freshly baked lamp, the presence of too much residual gas in the cylinder, which for those types of devices that are prone to the occurrence of thermal current in the circuit of the first grid (primarily lamps with a high slope, for example EL84, EL34), further reduces Reliability of operation in fixed bias mode.

A new method for testing and selecting output tubes - the three-point method

When testing lamps for flux, the task of reducing the labor intensity of this process becomes particularly important. It is also necessary to maintain or improve the accuracy of measurements.

The measurement accuracy is influenced by both the measurement technique itself and the quality of stabilization of the voltages used in the circuit. Labor intensity is influenced by the need to control these stresses. It follows from this that in order to reduce the labor intensity of the process, it is necessary to minimize the number of voltages used in the circuit.

The minimum set of voltages sufficient to test lamps in a variety of modes of interest to us consists of filament voltage, high voltage and bias voltage.

A stable filament voltage is obtained from a winding wire of a transformer connected to a stabilized alternating current network, wound with a sufficiently thick wire (to avoid sagging under the load that varies depending on the type of lamp being tested). In our case, an electro-mechanical type stabilizer is used, which provides the specified output voltage with an accuracy of 1%. The remaining voltages are obtained from adjustable electronic stabilizers. The high voltage in our installation is limited to 450 – 500 V.

The lamp testing process begins... with cleaning the base. The fact is that even from the factory the lamps come dirty. Then our special designations are applied.

Next, the lamp is installed on the stand, the filament is warmed up (the bias voltage source is always on), and high voltage is applied to the anode and screen grid. For some time, the lamp is additionally warmed up and brought to the maximum permissible mode for the power dissipated at the anode, in which it is maintained for at least 2 hours. In this case, you can observe the glow of the electrode system and draw appropriate conclusions regarding the quality of this lamp. Upon completion of this stage, the anode current Ia1 and the control grid current are measured. After this, the high voltage is reduced by the amount dU2 at a constant bias voltage. The lamp switches to another mode, a new value of the anode current, Ia2, is measured. Then we reduce the bias voltage by the amount dU1 at a constant high voltage and measure the new value of the anode current, Ia3.

In principle, this ends the lamp testing program. The whole process takes 2.5 – 3 hours.

Estimation of the slope of the lamp characteristic using the first grid:

S1 = (Ia3 - Ia2)/dU1

Estimation of the slope of the lamp characteristic using the second grid:

S2 = (Ia1 - Ia2)/dU2

In the last formula we neglect the influence of the anode (high) voltage on the anode current. With this test method, a phenomenon such as thermal inertia of lamps becomes noticeable, which manifests itself during their slow transition from one mode to another. Therefore, when changing the electrical mode, measurements are performed only after the new thermal mode has been established.

The criterion for selecting pairs and quartets of lamps is that the spread of anode currents in each of the three measured operating points should be within 2%. It should be noted that this is a rather stringent requirement that guarantees the pairing of lamps in a variety of modes that differ significantly from the test ones.

Based on the values ​​of the anode current at all three points and the slope of the characteristics on the first grid, the lamps are sorted into the categories Compressed Distortion - Dynamic Clean, the number of varieties depends on the volume of testing of lamps of the same type.

The article is devoted to the practical measurement of the static anode-grid characteristics of radio tubes in kitchen conditions close to combat conditions.
It's no secret that in lamp designs it is useful to know what parameters the lamps have, especially if they have been used for some time. I set myself the task of achieving results strictly on a budget and using available materials and tools.

Measuring stand with lamp sockets and sockets,
including 3 power supplies and meters plus cords with plugs

Idea

The idea of ​​having a decent tube tester came to me relatively long ago, but I moved in this direction slowly and sadly, stumbling over my own laziness along the way. Additionally, I was slowed down by obstacles in the form of analyzing schemes that fell under the hot hand, often contradictory, posted on the vast expanses of the Internet and in books.

The last straw that broke my patience was eBay, which demonstrated simply astronomical prices for such devices. So, the Hickok TV-2C/U TV-2 TV2 Mutual Conductance Tube Tester, which I liked but was used, costs today about 850 American rubles plus 250 for shipping. And to it you also need to add a network trans of 110 Volts, 200 watts, if not more.

Nearby, in the same eBay, I happily noticed our dear, 21-kilogram and very convincing Kalibr L3-3 Russian, new, which will be sent directly from Ukraine, but its price tag was a significant 850 plus postage 280, a total of 1130 of the same green, American.

When analyzing the circuit solutions of factory and amateur designs, I often did not have much confidence in the objectivity of the readings of their beautiful color “display meters” with the result “good” or “bad”.

I only wanted to measure the anode currents, allowing me to objectively assess the emission of the lamps, within the error limits of my measuring instruments.

What is inside?

Upon closer examination, I discovered that the coveted unit is nothing more than a number of lamp panels for measured lamps, 3 adjustable power supplies, voltmeters-milliammeters for monitoring currents and voltages, and intricate switching of all of the above equipment.

The filament and grid power supplies did not raise any questions, especially since I already had ready-made factory designs on the farm, but the anode voltage source at +250V was of some concern. From there I began moving towards my cherished goal.

At the beginning, using the method of successive approximation, a separating trans for electric shavers, 220/220V, 15W, built under plaster, for the bathroom, went into battle. Without hesitation, I soldered a diode bridge with electrolyte, borrowed from some former monitor, to its secondary. Then I plugged it into the network.

And what have we got off the hook? Of course, +310V: no: But I need 250.
I somehow didn’t want to unwind the secondary, and the next step was to take out from the bins an old, but quite working thyristor power regulator. I twisted the handle down and - voila +250 anode is there.

Attempt number one, with a whistle and a technical break

For a start, of course, it’s not bad, and the solution as a whole is workable, but for EL 34 I need a good 100 anode milliamps (not counting 15 mA for the second grid), and they turned out somehow with difficulty, I’m already silent about the interference from the thyristor on standing nearby on a shelf, and a randomly turned on radio.

But when testing the circuit, a new problem emerged: as soon as the 34 warmed up, it suddenly became excited, and the peacefully singing receiver suddenly whistled and wheezed like a robber nightingale with a cold. The anode current doubled, and the voltage actually dropped under such a load.

Since changing my lamp is temporarily “out of the question,” I, by a willful decision, short-circuited the 1st grid through a capacitor to the ground. The excitement probably took offense at me, but immediately disappeared.

Of course, it would be possible to make a high-voltage anode power supply using bipolar or field-effect transistors, but it is also prone to self-excitation, burns out if shorted, and I didn’t have 250 Volt zener diodes in my bins.

After some thought, I decided to use LATR to install the anode, but the trouble is that I still haven’t bought it.

I didn’t like the price of 170 evergreens, and the sizes were somehow too large. Plus galvanic connection to the network. Here I again had a long-term technical break...

In the end, everything turned out differently, and much better. Once I successfully bought an ancient transformer with a bunch of taps on the secondary. It honestly once powered the TV, but now, although with the original switch, it was left not only homeless, but also completely without a housing. And here he is, in person.

Attempt number two, victorious

It was in this way (or something similar) that my classic anode transformer design matured - simple and indestructible.

And this is the overall result: a measuring stand with lamp panels and sockets, including 3 power supplies and measuring instruments, plus cords with plugs.

To measure possible interelectrode short circuits, I additionally built a probe on a neon light bulb (Figure 1).

They are supposed to sequentially test all the terminals of the lamp relative to the cathode to which we connect the ground. Then we test relative to the grid and so on until all the electrodes run out: wink:
This test is done on a cold lamp, then on a warm lamp. Although the same results can be achieved by measuring interelectrode resistances with a conventional ohmmeter.

During the tests, it seemed to me advisable to apply the anode voltage last and turn it off first, although I tested the simultaneous supply of all voltages and did not cause any complaints.

I do not pretend to be particularly original in solving the problem, but measuring the anode current, and thus determining the spread and residual life of the lamps that I will use in the amplifier, turned out to be quite sufficient for my needs. With minimal changes, this tester can measure a wide variety of lamps.

Figure 2 shows a block diagram of measuring the anode current depending on the triode grid voltage with the additional function of monitoring the vacuum of the lamp.

In the case of a tetrode/pentode, the circuit is supplemented with a 2nd grid circuit (Figure 3).

I apologize for the lack of a filament circuit - sPlan 7 does not give me filament in pentodes: ireful:

In addition to monitoring serviceability, the tester allows you to measure the anode-grid characteristics of lamps. To do this, it is necessary to apply a series of voltages to the first grid, obtain the corresponding anode currents and construct a graph point by point. Here it is advisable to avoid excessive fanaticism and take into account the maximum permissible power dissipation of the anode (and the second grid for tetrode-pentodes). The reference point is the graph from the reference book - and we follow it. Or you can, for example, measure 3-4 anode currents in the operating range of a specific circuit and select pairs - quartets with similar parameters.

Practical implementation of a lamp tester

The practical implementation of the tester is very close to the block diagram with the only difference being that the batteries for the filament and the 1st grid are replaced with stabilized laboratory power supplies (Figure 4).

The lamp sockets are soldered into sockets, and power supplies and measuring instruments are connected to them with connecting cords.

I used the multimeters I had available as measuring instruments, and the heat was monitored by the digital voltmeter and ammeter built into the laboratory power supply.

The anode and the 2nd grid are powered from a transformer with a switchable secondary winding, a bridge and 2 electrolytes. Rough setting of the anode voltage is carried out by switching its secondary winding, and for precise setting use potentiometer R5.

C2 in the first grid circuit eliminates possible excitations of the lamp; by opening the SW1 button, the vacuum is controlled - the grid circuit becomes high-resistance and with a poor vacuum in the lamp, the anode current will noticeably increase. Button SW2 is used to control the absence of an intra-lamp short circuit between the cathode and the heater - normally, when it is pressed, the anode current should sharply go to zero.

Lamp emission control idea

The idea of ​​controlling lamp emission is straightforward: the data sheet for each lamp specifies the anode current at given anode and grid voltages. I set these voltages (including filament voltage), wait for the lamp to warm up and control the anode current. According to the reference book, the anode current is 100% of the lamp emission. If the measurement shows a lower current, the lamp is worn, and if the value is less than 40-50%, the lamp must be replaced.

I consider a nice feature of the tester to be the limitation of current surge through the filament when turned on due to the use of a laboratory power supply with current limitation.

Setup and use

The tester did not require any special setup, but I strongly recommend being careful with the anode voltage, the visualization of which is solved on neon HL2. Good insulation of the handle of resistor R5 is also necessary.

Considering that so far I was only interested in ECC81 and EL 34 lamps, I present their data taken from.

The tester provides an additional opportunity to judge the wear of lamps by the drop in the anode current when the filament voltage decreases. For a good lamp, a 10% decrease in filament voltage should cause a smaller (in percentage) decrease in the anode current, all other things being equal.

It is known that a 5% or even 10% reduction in filament voltage can significantly extend the life of lamps.
Later, when the lamp's emission weakens, it will be possible to return the filament to its original value. True, manufacturers do not recommend combining the maximum anode current and the minimum filament voltage. Well, I didn’t recommend that.

What will the respected community say about this: will we reduce the tension or not?

Literature:

L.A. Dudnik “Testing electron tubes”
I.G. Bergelson, N.K. Daderko, N.V. Password, V.M. Petukhov “Receiving and amplifying lamps of increased reliability”
E.L. Chafi "Theory of vacuum tubes"
A.L. Bulychev, V.I. Galkin, V.A. Prokhorenko “Handbook of electrovacuum devices”

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The device (Fig. 4-4) is designed to measure basic electrical parameters and measure the static characteristics of radio tubes such as receiving-amplifiers, low-power generators (power dissipation at the anode up to 25 W), kenotrons, diodes and gas-filled zener diodes.

Main technical characteristics

1. The L1-3 device allows you to perform the following types of tests: checking diodes for emission current or anode current;

checking triodes, double triodes, tetrodes, pentodes and combined lamps for anode current, first grid current, second grid current, anode current, slope of the anode current characteristic, slope of the heterodyne part of the characteristic of frequency-converting lamps, anode current at the beginning of the characteristic and blocking voltage of the first grids; checking gas-filled zener diodes for ignition potential, voltage and relative degree of stabilization when current changes. 2. The device provides measurement of the leakage current between the cathode and the lamp heater at voltages of 100 and 250 V (plus - on the cathode, minus - on the heater), as well as the rectified current of kenotrons when powered from networks with a frequency of 50 Hz.

3. Basic measurement errors at ambient temperature +20±5°С and relative humidity 65+15% of filament voltage, anode, grids, anode and grid (second grid), as well as rectified current - no more than ±10%; currents using an electronic microammeter - no more than ±2.5%; characteristics slope - no more than +2.5%.

4. The device is operational when powered by a voltage of 110, 127 and 220 V with a frequency of 50 Hz or a voltage of 115 V with a frequency of 400 Hz, can be operated continuously for 8 hours at an ambient temperature of +35 ° C and tested various types of lamps with anode current up to 100 mA for 2 hours with continuous testing of lamps of the same type with an anode current of 100 mA or more; has protection of the dial indicator from overloads.

5. Power consumption - no more than 300 VA (when testing a 5TsZS lamp - no more than 450 VA).

Prishra scheme

The block diagram of the L1-3 device is shown in Fig. 4-5.

The power supply supplies constant voltage to the anode, grids and filament of the lamp under test, as well as to the slope meter and electronic microammeter.

The slope meter consists of an electronic voltmeter and a generator and is used to measure the slope of the anode-grid characteristics of receiving-amplifier and low-power generator tubes. The generator produces a sinusoidal voltage with a frequency of 1200 Hz to supply it to the grid of the lamp under test. An electronic voltmeter is designed to measure alternating voltage with a frequency of 1200 Hz, taken from the anode load of the lamp under test.

An electronic microammeter is used to measure the reverse current of the first grid, the anode current at the beginning of the characteristic and the leakage current between the electrodes of the lamp.

The switching device is designed to connect the power supply and electrical measuring equipment to the electrodes of the lamp under test.

The schematic diagram of the L1-3 device (Fig. 4-6) consists of four main parts: a power source, a slope meter (electronic voltmeter and generator), an electronic microammeter and a switching device.

The power supply includes a power transformer T, three kenotron rectifiers, a semiconductor diode rectifier and three electronic voltage stabilizers. The rectifier, assembled on the V3 lamp (5Ts4M), provides constant voltage to the anode and the second grid of the lamp under test, as well as to the slope meter, having three outputs to electronic stabilizers.

The electronic stabilizer for stabilizing the anode voltage of the lamp under test consists of lamps VI and V2 (6P1P) and lamp V4 (6Zh4P). The rectified voltage is smoothly regulated within 5...300 V by potentiometer R76.

The electronic stabilizer for stabilizing the voltage on the second grid of the lamp under test consists of lamps V8 (6P1P) and V9 (6Zh4P). The rectified voltage is smoothly regulated within 10...300 V by potentiometer R112.

The 250 V electronic stabilizer on lamps V16 (6P1P) and V17 (6Zh4P) serves as the power source for the slope meter. The voltage is adjusted using potentiometer R169. At the same time, part of this voltage is used to calibrate the microammeter.

The second rectifier, the voltage of which is stabilized by gas-discharge zener diodes V6 and V7 (SG2P), is assembled on a V5 lamp (6Ts4P). The voltage of this rectifier is the reference voltage for the electronic stabilizers and is used as a bias voltage on the first grid of the lamp under test.

The third rectifier, assembled on lamps V11 (6Ts4P) and V10 (SG2P), serves as the power source for the electronic microampere meter.

The fourth rectifier, assembled on semiconductor diodes V19...V26 (D7G) in a bridge circuit, supplies the filament of the lamp under test with a constant voltage. This voltage is set using potentiometers R32 and R38.

The voltage supplying the device is adjusted by rheostat R87 with the NETWORK button pressed. The indicator arrow should be set opposite the red line (mark 120).

The slope meter is calibrated by applying a voltage of 120 mV to the input of the electronic voltmeter, which is removed from the generator divider through toggle switch 55, which ensures that the measurement accuracy is maintained regardless of changes in the sensitivity of the voltmeter or the generator voltage.

Adjusting the frequency of a 1200 Hz generator assembled on a V15 (6NZP) lamp according to the RC generator circuit with a Wien bridge, in small

limits is carried out by changing the resistance of resistor R155 of one of the bridge arms; adjusting the generator output voltage by changing the depth of negative feedback using potentiometer R167. The voltage from the cathode of the second half of the V15 lamp is supplied to the divider, and from it to the grid of the lamp under test.

An electronic voltmeter is designed to measure alternating voltage with a frequency of 1200 Hz, taken from the anode load of the lamp under test. The voltmeter uses a selective amplifier assembled on lamps V12, V13 (6Zh4P) and V14 (6PZP). To obtain high selectivity, the amplifier has two double T-bridges. The voltage is rectified by germanium diodes V27 and V28 (D106A), operating in a doubling circuit. To stabilize the operation of the amplifier, it uses negative feedback through double T-shaped bridges.

An electronic microammeter is used to measure the reverse current of the first grid, the anode current at the beginning of the characteristic and the leakage current between the electrodes of the lamp under test. It is assembled on a V18 lamp (6NZP) according to a balanced circuit. When measuring current, a dial indicator is connected between the cathodes of the V18 lamp. Balancing the circuit (triodes of the V18 lamp), i.e. setting the indicator to zero, is done with potentiometer R123. Calibration of the electronic microammeter (setting its sensitivity) is carried out by potentiometer R125 when applying a stabilized voltage of 250 V, supplied from the electronic stabilizer of the slope meter (from the divider R93...R99 through resistor R102).

Working with the device

To prepare the L1-3 device for operation, you must:

Place the fuse holder in the position corresponding to the mains voltage. Set the knobs for adjusting the filament voltage, grids and anode to the left extreme position (counterclockwise), switch S2 PARAMETERS to position S, switch S1 INSULATION to position PAR.

Place the required test card on the plug switch and fill all the holes on the card with plugs.

Apply power to the device by turning on the S3 POWER switch (the signal light should light up). Using the NETWORK knob while pressing the button

NETWORK, set the indicator arrow opposite the red line (mark 120), periodically monitoring the supply voltage while working with the device.

After 10...15 minutes of warming up, calibrate the slope meter. To do this, toggle switch S5 must be set to the CALIBER position. and, by pressing the S6 MEASUREMENT button, use the potentiometer R129, the axis of which is located under the slot, to ensure that the indicator arrow is positioned opposite the red line. Upon completion of calibration, move toggle switch S5 to the MEASURE position.

Set the zero and calibrate the microammeter. To do this, switch S2 PARAMETERS must be moved from position S to position Ici, toggle switch S4 MKA must be set to position MEASURE. and by pressing the S6 MEASUREMENT button, use potentiometer R129 to set the indicator needle to the zero scale mark. To calibrate the microammeter, toggle switch S4 of the MKA must be moved to the CALIBRATE position. and by pressing the S6 MEASUREMENT button, use potentiometer R125 to set the indicator arrow opposite the red line. For greater accuracy, the process of zeroing and calibrating the microammeter should be performed several times. Upon completion of calibration, move the MKA toggle switch S4 to the MEASURE position. It is prohibited to move this toggle switch to the CALIBRATE position. with the lamp under test inserted into the panel.

Before measuring the parameters of a direct-heat lamp, it must be kept for 3 minutes to set its modes; indirect-heat lamps - 5 minutes.

To check the parameters of triodes, tetrodes and pentodes you need:

Insert the lamp under test into the panel indicated on the test card, and using the PARAMETERS switch and potentiometers Uci, FLASH, UA, Uc2 in the sequence indicated on the test card, set the required voltage values.

Determine the leakage current between the lamp electrodes. To do this, move the PARAMETERS switch to the ISOL position. and measure the insulation between the grids, the first grid and the cathode, the cathode and the heater by setting the INSULATION switch S1 to the appropriate positions and pressing the MEASURE button. The leakage current is measured using the instrument scale.

To measure other parameters of the lamp under test, move the INSULATION switch to the PAR. position, the PARAMETERS switch to the IA I c2 S I c1 position and, pressing the MEASUR button, sequentially take readings from the dial indicator of the device.

In order to increase accuracy, before measuring the slope, check the calibration of the slope meter, and when checking each subsequent lamp, check the filament voltage.

Make any switches while pressing the MEASUR button. prohibited. The NETWORK and MEASUREMENT buttons must be pressed when setting the filament voltage.

To check the parameters of kenotrons you need to:

After filling all the holes of the test card with plugs, set the INSULATION switch to the PAIR position, and the PARAMETERS switch to the I rect position

Turn on the device, insert the lamp under test into the panel, set the filament voltage, then press the MEASUREMENT button and use the indicator to determine the strength of the rectified current. When measuring rectified current, it is prohibited to set the INSULATION switch to the 1akhv position.

It should be remembered that kenotrons can be checked when the device is powered only from a network with a frequency of 50 Hz.

To check the diode parameters you need to:

Before starting the measurement, set the ISOLATION switch to the CC position, the PARAMETERS switch to the ISOLATION position.

Calibrate the microammeter before placing the diode test card on the switch as described above, if such calibration has not been done before. In this case, it is necessary to fill holes 20/1, 26/1, 40/P and 52/P with plugs.

Place the test card on the plug switch, insert the lamp into the panel, set the filament voltage and, with the MEASURE button pressed, measure the conduction current between the cathode and the diode heater.

4. After warming up the lamp, measure the emission current (anode current). The procedure for measuring the electron emission current in cases where the minimum and maximum permissible values ​​of the electron emission current are specified (in cases where the set anode voltage is indicated at the top of the test card, and the anode current at the bottom) is as follows: PARAMETERS switch from the ISOL position. it is necessary to move to the Id position and, with the MEASUREMENT button pressed, use the Ua knob to set the anode voltage indicated on the card, after which the PARAMETERS switch should be moved to the Ia position. Then, with the MEASUREMENT button pressed, the INSULATION switch must be moved from the KN position to the PAR position. and use the dial indicator to count the electronic emission current, after which the INSULATION switch is again moved to the KN position. The duration of measurement in this case (the time from the moment the INSULATION switch is moved from the KN position to the PAR position and back) should be no more than 2 s.

The procedure for measuring the electronic emission current in cases where only the lowest permissible value of the electronic emission current is specified (in cases where the set emission current 1a is indicated at the top of the test card, and the voltage UA at the bottom) is as follows: PARAMETERS switch, from the ISOL position. must be moved to position Ia, and the INSULATION switch from the KN position to the PAR position. Then, with the MEASUREMENT button pressed, use the UA knob to set the anode current (emission current) indicated on the card, after which the PARAMETERS switch must be moved from position Ia to position Ua and with the MEASURE button pressed, read the value of the anode voltage using the dial indicator. The INSULATION switch must then be set back to the KN position. The duration of measurement in this case (the time from the moment the INSULATION switch is moved from the KN position to the PAR position and back) should be no more than 5 s.

To check gas-filled zener diodes you need:

Set the INSULATION switch to the PAR. position, and the PARAMETERS switch to the UA position.

By pressing the MEASUREMENT button, use the potentiometer Ua to smoothly apply voltage to the lamp until it ignites and record the ignition voltage using the device indicator.

Switch the PARAMETERS switch to position Ia and use the potentiometer UA to set the minimum and maximum current values ​​indicated on the test card.

At extreme current values, set the PARAMETERS switch again to position Ua and count the combustion voltage value.

The change in stabilization voltage is determined by the difference between the voltages of the

rhenium, measured at the maximum and minimum current values, with a deduction of 1 V (voltage drop across the milliammeter shunt at the maximum current value of the zener diode under test).

To measure the anode current at the beginning of the anode characteristic of the lamp, you need to:

1. Having prepared the device for operation, set the INSULATION switch to the position

Using the PARAMETERS switch and potentiometers Uci, UH, UA and Uc2, achieve the required voltages on the electrodes of the lamp under test (their values ​​are indicated on test card No. 1, specially designed for these measurements).

Switch the PARAMETERS switch to position 1akhv and read the current strength according to the dial indicator of the device.

If you set a certain value of the anode current indicated on the test card or in the technical specifications for the lamp, you can measure the blocking voltage of the grid by moving the PARAMETERS switch to the Uci position.

When characterizing lamps, you must be guided by the following:

1. To take characteristics, you should use key test card No. 1, on which all 144 holes available on the plug switch are punched, indicating the numbers and purposes of the holes. The holes on the map are divided into two groups: upper (I) and lower (II). The holes of each group are designated from 1 to 72 inclusive. In the future, the number of each hole will be indicated by a fraction, the numerator of which shows the hole number, the denominator - the group number. For example, hole 2/1 denotes the second hole of the upper group, hole 1/II - the first hole of the lower group.

Before reading the characteristics, set the knobs NAKAL, Uci, Ua and Uc2 to the left extreme position (counterclockwise). Then, having placed a key card on the test card for the given type of lamp under test and determined in the light which holes on it should be filled with plugs, perform this operation. In the absence of a test card (for testing new lamps), knowing the pinout of the lamp, determine from the circuit diagram of the device the numbers of holes that need to be filled with switching plugs.

Insert the lamp under test into the appropriate panel of the device, keeping in mind that

To supply the filament voltage (15 V), the first grid (75 V), the second grid (300 V) and the anode (300 V), it is not necessary to insert plugs into the switch. It is prohibited to simultaneously fill two holes of the same voltage, same current and transconductance on the switch with plugs.

The supply of voltage to the lamp under test begins with filament, for which, starting from hole 22/P, which corresponds to the minimum filament voltage, it is necessary to sequentially move the switching plug into the following holes until the required filament voltage is set using the TILM knobs (RUBLY and SMOOTH) . To connect a dial indicator to a filament voltage source when powering the filament with direct current, holes 69/P, 70/P, 66/II and 72/N must be filled with plugs, and when powered by alternating current - holes 63/P, 64/II, 65/P and 71/II.

A bias voltage of up to -10 V is applied to the first grid of the lamp under test by filling hole 2/1 with a plug, and up to -65 V by filling hole 1/1; Smooth adjustment of the bias voltage is made using the Uci knobs labeled -10 and -65.

When testing all types of lamps, except gas-filled zener diodes, the commutation plug must be inserted into hole 12/P to short-circuit the ballast resistor R56 in the anode circuit of the lamp.

To supply a constant anode voltage to the lamp under test, you need to fill holes 25/1, 46/P and 58/11 with plugs (with the Ua handle, the voltage can be changed within 15... 140 V); holes 26/1, 52/P and 40/11, if the voltage at the anode needs to be adjusted within 140 ... 300 V.

A constant voltage is supplied to the second grid of the lamp under test in the range of 10 ... 140 V by filling holes 19/1, 46/P and 58/P with plugs, within 140 ... 300 V - holes 20/1, 52/II, 40/II; Smooth voltage adjustment on the second grid is carried out using the Uc2 handle.

If the voltage at the anode of the lamp under test should be greater than 140 V, and the voltage on the second grid should be less than or equal to 140 V, then holes 19/1, 26/1, 40/P and 52/P should be filled with plugs. If the anode voltage of the lamp under test should be less than or equal to 140 V, and the voltage on the second grid should be more than 140 V, then holes 20/1, 25/1, 40/I and 52/I must be filled with plugs.

To supply low anode voltages up to 15... 20 V (for example, when characterizing diodes), it is necessary to fill holes 5/11, 6/P, 11/11, 48/P, 60/N and 25/1 with plugs.

10. To avoid a short circuit of part of the turns of the power transformer T of the device, as well as a short circuit of the gas-filled zener diode V7 (SG2P), it is prohibited to simultaneously fill with plugs any two or more holes inside the following groups: a) 40/I, 46/N, 48/I ; b) 52/11, 58/P, 60/11; c) 25/1, 26/1; d) 19/1, 20/1.

11. The characteristic of the lamp under test is measured in the usual way. For example, to measure the anode-grid characteristic, it is necessary to change the voltage on the first grid (the PARAMETERS switch should be set to position Uci) and record the change in the anode current of the lamp (the PARAMETERS switch should be set to position 1a).

Semiconductor Testing

One of the main electrical parameters by which semiconductor diodes are rejected include the reverse current of the diodes I reverse and the forward voltage drop across it U pr for transistors - current gain h 21 (a β), output conductivity h 22 and reverse collector current I k.o

Rejection is done when the parameters during measurement do not fall within certain limits. For example, if the current Ic exceeds the maximum guaranteed limit for a given type of transistor by more than 2 ... 3 times or continuously increases over time, then such a transistor is unsuitable for use. Transistors with β =5 ... 8 or less are also rejected.

When measuring the parameters of semiconductor devices, the integrity of their electron-hole junctions is checked.