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 to reduce the number of lamp parameters used in the design.
Today this approach will not work. By definition, new-made lamps do not imply serious use (but the fetishization of lamps flourishes), with all the ensuing consequences. Well, who takes a guitar amp seriously other than the user and his absurd neighbors? Few people check even the elementary correspondence of the output power (and it depends on the selection of lamps) to the passport value in the process of servicing the equipment!
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's warehouses (there the lamps had far from sound priorities), but could remain as unclaimed cull or something like that. Who knows?
Thus, on the one hand, we have lamps, the characteristics of which have a significant spread, and on the other hand, subjectivity, “taste” in the evaluation of the operation of the equipment (it is also sound). The last extra "degree of freedom" cannot be eliminated.
So the lamps must be subjected to careful testing and selection. Do not write on the packaging of the lamp one single, hastily removed, value of the anode current in no-understand-what mode - this is not a selection! And to give an adequate set of parameters. This is exactly what good sellers do. And we are worse?
It would seem that there are quite accessible lamp meters like the domestic L3-3 (and less accessible American ones, Hickok). These instruments allow you to perform a wide range of tests with hundreds of types of lamps.
They also have their limitations, which do not allow us to solve all our problems. So, for example, it is impossible to “fry” a 6550-type lamp on L3-3 properly. And the excellent emission indicators of some small lamp, recorded with the help of such devices, indicate the operability of the lamp, with which consumer equipment will be unsuitable for use due to the microphone effect or noise. Add here the "charms" of reading on the 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 audio equipment using specialized tools that have to be manufactured independently.
I would like to note in this matter the importance of stabilizing the supply voltages in the equipment, whether it be glow, bias or high voltages.
Preamplifier test
Most of the tubes used in audio equipment are double triodes with the same halves, in a finger design. Exceptions are rare and exotic, requiring individual consideration. This is where the specificity of mass testing of lamps for commercial purposes comes from.
In addition to rejecting unusable instances, the task is to select instances with special properties:
Instances with more or less gain (for example, high gain);
- low noise and non-microphone (V1, low noise);
- with the same gains of the 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 (with the exception of rare special cases), it is important that it more or less fit into the norms for lamps of this type, and the "bracing" of the halves was within certain limits.
The test bench allows you to implement the typical electrical modes most often found in audio equipment and conduct specialized tests for the range of lamp types of interest.
The lamp is mounted on a stand, high voltage is applied after the cathode is warmed up. Then the lamp trains for some time (from 20 minutes), the voltage at the anodes is controlled. An alternating voltage is supplied to the stand input from the generator, the voltage amplified by each triode is measured. According to the result, one can judge the amplifying abilities 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 permissible for most lamps. We judge the quality of the insulation by the magnitude of the current flowing in this circuit (it is scanty). In general, lamps for serious applications are subject to a more severe test of about 250 V, which can also be provided if you are willing to pay extra.
The next stage of the test is subjective. The stand with the lamp under test is placed about 1 foot in front of a guitar cabinet with a twelve-inch speaker connected to a high-gain guitar amplifier, tuned so that the guitar gives a clear “JJ” 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 bulb of the lamp under test, are connected in turn to the input of the guitar amplifier.
Prone to microphone effect, the lamp instantly gives itself away with a loud and joyful pig squeal. In addition, by tapping a kind of 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, color, level - it is quite difficult to adequately measure. But some experience of the user of high-gain guitar amplifiers allows you to get an assessment just in the form that is required - in an emotional way, because this is what the point of using tubes ultimately boils down to.
Output Lamp Test
Assume that the lamp is a pentode or beam tetrode, it is these lamps that are used in the output stages of the vast majority of tube amplifiers.
The lamp test begins by applying voltages to the electrodes in the proper order. The first time the lamp works in light mode. If no signs of obvious unsuitability of this instance are found, we proceed 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 circuit of the first grid. The variable component of the anode current is measured. From this value, the steepness of the first grid is calculated.
An alternating voltage is introduced into the circuit of the second grid, and the variable component of the anode current is measured. From this value, the slope of the second grid is calculated.
The unit then switches back to light mode. Anode current at reduced power dissipated by the anode (approximately 20% of maximum). This additional reference point is of some value for selecting pairs of lamps that are to be operated in Class AB or B push-pull stages.
Thus, we get a set of parameters sufficient for grouping lamps into pairs or quadruples. The basis for rejecting the lamp may be the "outstanding" values of these parameters, especially the abnormally high value of the current of the first grid. 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 (first of all, these are lamps with a high steepness, for example EL84, EL34), further reduces reliability of operation in fixed-bias mode.
A new method for testing and selecting output lamps - the three-point method
When testing lamps for flow, the task of reducing the complexity of this process is of particular importance. It is also necessary to maintain or improve the accuracy of measurements.
The measurement accuracy is affected by both the measurement technique itself and the quality of stabilization of the voltages used in the circuit. The complexity is influenced by the need to control these voltages. It follows from this that in order to reduce the complexity 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.
We obtain a stable filament voltage from a winding wire of a transformer connected to a stabilized alternating current network, wound with a sufficiently thick (to avoid drawdown under a load that changes depending on the type of lamp under test) wire. In our case, an electro-mechanical type stabilizer is used, which provides a given 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 process of testing lamps 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 heated (the bias voltage source is always on), high voltage is applied to the anode and the screen grid. For some time, the lamp is additionally warmed up and brought to the maximum permissible mode in terms of power dissipated on the anode, in which it is maintained for at least 2 hours. In this case, one can observe the glow of the electrode system and draw appropriate conclusions regarding the quality of this lamp specimen. Upon completion of this stage, the anode current Ia1 and the control grid current are measured. The high voltage is then reduced by dU2 while the bias voltage remains unchanged. The lamp switches to another mode, the new value of the anode current, Ia2, is measured. Then we reduce the bias voltage by the value dU1 at a constant high voltage and measure the new value of the anode current, Ia3.
In principle, the lamp test program ends here. The whole process takes 2.5 - 3 hours.
Estimation of the steepness of the characteristics of the lamp on the first grid:
S1 = (Ia3 - Ia2)/dU1
Estimation of the steepness of the characteristics of the lamp on 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, such a phenomenon as the thermal inertia of the lamps becomes noticeable, which manifests itself when they slowly transition from one mode to another. Therefore, when changing the electrical mode, measurements are performed only after the new thermal mode is established.
The criterion for selecting pairs and quartets of lamps is that the spread of anode currents at each of the three measured operating points should be within 2%. It should be noted that this is a rather strict requirement, which guarantees the pairing of lamps in a variety of modes that differ significantly from the test ones.
According to the values of the anode current at all three points and the steepness of the characteristics for the first grid, the lamps are sorted into the Compressed Distortion - Dynamic Clean category, the number of grades depends on the volume of tests of the same type of lamps.
The preliminary test is intended to determine the integrity of the lamp filament and the absence of short circuits between its electrodes.
Such a test is carried out with an ohmmeter or a NL neon lamp (Fig. 1). In this case, it is only necessary to observe whether the current passes if the device is connected to the terminals of the filament on the lamp base, and whether it is absent if the device is connected to other electrodes. Most static lamp testers provide for a convenient and quick pre-test of this kind.
Rice. 1. Preliminary tests of lamps.
a - to break the thread; b - for a short circuit between the electrodes.
Static lamp test represents the determination of all parameters of the lamp, but it requires rather complex apparatus and is carried out only in laboratories. In the workshops for static testing of lamps, simplified instruments are used, called lamp testers or lamp testers.
Emission measurement. Most testers allow you to determine the emission of the cathode, that is, the cathode current of the lamp at certain constant voltages on its electrodes, which are indicated for various types of lamps by the manufacturer in special tables attached to the tester: the tester's device includes potentiometers and switches that allow for these tables to reproduce the required test mode. The anode current obtained under these conditions is considered a criterion for the suitability of the lamp.
The scale of the anode current indicator is often not graduated, but is divided into two or three sectors with designations: good, suitable and unsuitable. When testing lamps on a tester with a scale calibrated in percent, lamps are considered good if they give at least 70% of the normal anode current; at 50-69% they are considered still suitable, and below 50% the lamps are rejected altogether. The determination of emissions in a simplified way can be carried out without the help of a special tester. To do this, it is enough to have at hand a source of voltages necessary for testing the lamp and a milliammeter (Fig. 2 a).
Rice. 2
a - Simplified method for measuring cathode emission.
b - Measurement of the steepness of the characteristic
Slope measurement. Constant voltages are applied to the electrodes of the tested lamp, corresponding to its normal operating mode, including the grid bias voltage, which must correspond to the selected operating point. Having determined the anode current of the lamp using a milliammeter (Fig. 2 b), reduce the grid bias by exactly 1 V and again note the anode current.
The increase in the anode current in milliamps determines the static slope of the characteristic in mA / V.
Vacuum test. To test the vacuum, the lamp is connected to a circuit similar to that of measuring the emission or slope of the characteristic, and the negative voltage on the control grid must correspond to the choice of the normal operating point. Having noticed the value of the anode current, a resistance of 1 MΩ is introduced into the control grid circuit (Fig. 3) and the change in the anode current is observed.
The proposed device is intended for testing radio tubes with an octal base and finger tubes with a seven- and nine-pin base, as well as low-power transistors of the p-p-p and p-p-p type.
When testing radio tubes, the device is powered by an alternating current network of 127/220 V and consumes up to 12 W, and when testing transistors from an internal DC battery KBS - L - 0.50 with a voltage of 3.7 V.
Radio tubes are tested for the integrity of the incandescent circuit, the absence of short circuits between the electrodes, the emission current, the absence of breaks between the electrode leads and the base pins. When testing transistors, the reverse current of the collector junction and the gain p are determined.
The schematic diagram of the device is shown in fig. I The device consists of a lamp tester, a transistor tester, a measuring circuit and a switching circuit
The lamp test circuit includes lamp sockets, P-G9 plug sockets. switch P1, power transformer, network terminals, fuse, signal light, switch P4b, P5, wire with a cap, plugs for supplying heat to the lamp under test, resistances R5, R6, diode D.
The transistor test circuit includes cartridges for clamping the transistor leads, a KBS-L-0.50 battery, and Rl-R4 resistances.
The measuring circuit includes the M592 device, the R7-RI0 universal shunt and the GIA switch.
The switching circuit includes switches P2 and PZ, P5, V2.
work of the tester of radio tubes
To check the radio tubes most commonly used by radio amateurs, you can limit yourself to all three tube panels: octal, seven-pin finger and nine-pin finger.
Before checking, the lamp is installed in the corresponding socket, the PZ switch is set to the “r-p-r, lamp” position, the device is connected to the mains, and switch B1 is turned on, and the signal light comes on. If the lamp under test has an electrode connected to the cap, the 1st clamp of the tester is put on it, connected to the 9th pin of the finger panel. To check the integrity of the filament, it is necessary to set the switch knob P1 to the number of one of the lamp filament terminals in accordance with the base, the switch knob 414 to the “off” position, the switch knob P2 to the short circuit position and remove the filament plugs from the sockets. With ^om, an alternating voltage of 25 V from the transformer will be applied to the filament of the lamp through the limiting resistance R5, diode D and a measuring device with a shunt. All other electrodes of the lamp are then connected to the body of the device. The deviation of the arrow of the device will indicate the integrity of the filament. During the check of the integrity of the filament, the filament scale of the device is turned on to the limit of 2.5 mA.
When testing a lamp for the absence of short circuits between the electrodes, they proceed in the same way as when checking the integrity of the filament. In this case, the switch 111 is alternately set to positions I-9. The absence of instrument readings indicates the absence of an electrode closure (the number of which is set by switch P1) with the rest of the electrodes. The deviation of the arrow of the device indicates a short circuit.
The lamp tester allows you to conditionally measure the emission current of radio lamps. The emission current in this case cannot exceed 10 mA. Therefore, according to the measurement results
The device (Fig. 4-4) is designed to measure the main electrical parameters and take static characteristics of such radio tubes as receiving-amplifying, low-power generator (dissipation power at the anode up to 25 W), kenotrons, diodes and gas-filled zener diodes.
Main technical characteristics
1. Device L1-3 allows you to perform the following types of checks: checking diodes for emission current or anode current;
checking triodes, double triodes, tetrodes, pentodes and combined lamps for anode current, current of the first grid, current of the second grid, anode current, slope of the anode current characteristic, slope of the heterodyne part of the characteristic of frequency converter 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 the current changes. 2. The device measures the leakage current between the cathode and the lamp heater at voltages of 100 and 250 V (plus - at the cathode, minus - at 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°C and relative humidity 65+15% of filament, anode, grid, anode and grid (second grid) voltages, as well as rectified current - no more than ±10%; currents using an electronic microammeter - no more than ± 2.5%; steepness of characteristics - no more than + 2.5%.
4. The device is operable 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, it can be continuously operated for 8 hours at an ambient temperature of +35 ° C and testing various types of lamps with anode current up to 100 mA within 2 hours with continuous testing of lamps of the same type with an anode current of 100 mA or more; has protection of the arrow indicator against overloads.
5. Power consumption - no more than 300 V. A (when testing a 5TsZS lamp - no more than 450 V. A).
Prishra scheme
The block diagram of the device L1-3 is shown in fig. 4-5.
The power supply provides constant voltage supply to the anode, grids and filament of the tested lamp, 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-amplifying and low-power generator lamps. The generator generates a sinusoidal voltage with a frequency of 1200 Hz to apply to the grid of the lamp under test. The electronic voltmeter is designed to measure alternating voltage with a frequency of 1200 Hz, taken from the anode load of the test lamp.
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 lamp electrodes.
The switching device is designed to connect to the electrodes of the tested lamp of the power supply and electrical measuring equipment.
The circuit diagram of the device L1-3 (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 a V3 lamp (5Ts4M), provides a constant voltage supply 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.
An electronic stabilizer for stabilizing the anode voltage of the test lamp consists of lamps VI and V2 (6P1P) and a lamp V4 (6Zh4P). The rectified voltage is continuously adjustable within 5...300 V by potentiometer R76.
An electronic stabilizer for stabilizing the voltage on the second grid of the tested lamp consists of V8 (6P1P) and V9 (6Zh4P) lamps. The rectified voltage is continuously adjustable within 10...300 V by potentiometer R112.
An electronic stabilizer 250 V on lamps V16 (6P1P) and V17 (6Zh4P) serves as a power source for the slope gauge. Voltage adjustment is made by 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 regulators and is used as the bias voltage on the first grid of the lamp under test.
The third rectifier, assembled on lamps V11 (6Ts4P) and V10 (SG2P), serves as a power source for an electronic microammeter.
The fourth rectifier, assembled on semiconductor diodes V19 ... V26 (D7G) in a bridge circuit, supplies the glow of the lamp under test with a constant voltage. This voltage is set using potentiometers R32 and R38.
Adjustment of the voltage supplying the device is carried out by the R87 rheostat with the NETWORK button pressed. In this case, 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, taken 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 lamp (6NZP) according to the RC generator circuit with a Wien bridge, in small
limits is carried out by changing the resistance of the resistor R155 of one of the arms of the bridge; adjustment of the generator output voltage - by changing the depth of negative feedback using the 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.
The electronic voltmeter is designed to measure alternating voltage with a frequency of 1200 Hz, taken from the anode load of the test lamp. 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 was assembled on a V18 lamp (6NZP) according to a balanced circuit. When measuring current, a pointer indicator is connected between the cathodes of the V18 lamp. Balancing the circuit (triodes of the V18 lamp), i.e. setting the zero of the indicator, is performed by the potentiometer R123. Calibration of the electronic microammeter (setting its sensitivity) is carried out by the potentiometer R125 when a stabilized voltage of 250 V is supplied from the electronic stabilizer of the slope meter (from the divider R93 ... R99 through the resistor R102).
Working with the device
To prepare the device L1-3 for operation, it is necessary:
Set the fuse holder to the correct position for the mains voltage. Set the knobs for adjusting the voltage of the glow, 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-in switch and fill all holes on the card with plugs.
Power up the device by turning on switch S3 MAINS (in this case, the signal lamp should light up). Using the NETWORK knob while pressing the button
NETWORK Set the indicator arrow opposite the red dash (mark 120), periodically monitoring the supply voltage while working with the device.
After 10 ... 15 minutes of warming up, calibrate the slope gauge. To do this, the S5 toggle switch must be set to the CALIBER position. and, by pressing the S6 MEASUREMENT button, use the potentiometer R129, the axis of which is brought out under the slot, to achieve the setting of the indicator arrow opposite the red line. At the end of the calibration, switch the S5 toggle switch to the MEASURE position.
Set zero and calibrate the microammeter. To do this, switch S2 PARAMETERS from position S must be moved to position Ici, toggle switch S4 MCA should be set to position MEASURE. and by pressing the S6 MEASUREMENT button, use the potentiometer R129 to set the indicator needle to the zero mark of the scale. To calibrate the microammeter, the S4 MCA toggle switch must be moved to the CALIBER position. and, by pressing the S6 MEASUREMENT button, use the potentiometer R125 to set the indicator arrow opposite the red line. For greater accuracy, the process of zeroing and calibrating the microammeter should be repeated several times. At the end of the calibration, switch the S4 MKA toggle switch to the MEASUREMENT position. It is forbidden to move this toggle switch to the CALIBR. with the lamp under test inserted into the panel.
Before measuring the parameters of a direct incandescent lamp to establish modes, it must be held for 3 minutes, for indirect incandescent 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, IGNITION, 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, switch 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 switch S1 INSULATION to the appropriate positions and pressing the MEASUREMENT button. Read the leakage current on the scale of the device.
To measure other parameters of the test lamp, turn the INSULATION switch to the PAR. position, the PARAMETERS switch to the IA I c2 S I c1 positions and, pressing the MEASURE button, sequentially take the readings of the dial indicator of the device.
In order to improve accuracy, before measuring the slope, check the calibration of the slope meter, and when checking each subsequent lamp, the filament voltage.
Perform any switching while pressing the MEASUREMENT button. prohibited. The NETWORK and MEASUREMENT buttons must be depressed when setting the heating voltage.
To check the parameters of kenotrons, you need:
After filling all the holes of the test card with the plugs, set the INSULATION switch to the PAIR position, and the PARAMETERS switch to the I rectified position.
Turn on the device, insert the test lamp 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 the rectified current, the INSULATION switch must not be set to the 1xv position.
It should be remembered that kenotrons can be checked when the device is powered only from a 50 Hz mains.
To check the parameters of the diodes, you must:
Before starting the measurement, set the INSULATION switch to the KC position, the PARAMETERS switch to the ISOLATION position.
Calibrate the microammeter before applying the diode test card to the switch as described above, if such a calibration has not been performed before. In this case, holes 20/1, 26/1, 40/P and 52/P must be filled with plugs.
Apply a test card to the plug-in switch, insert the lamp into the panel, set the filament voltage and, with the MEASUREMENT button pressed, read the conduction current between the cathode and the diode heater.
4. After the lamp has warmed up, measure the emission current (anode current). The procedure for measuring the electron emission current in cases where the smallest and largest allowable 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: switch PARAMETERS from the ISOL position. it is necessary to switch 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 switched to the Ia position. Then, with the MEASUREMENT button pressed, the INSULATION switch must be switched from the KN position to the PAR position. and read the electron emission current using the pointer indicator, after which the INSULATION switch is again set to the KN position. The duration of the measurement in this case (the time from the moment the INSULATION switch is switched from the KN position to the PAR position and back) should not exceed 2 s.
The procedure for measuring the electron emission current in cases where only the lowest allowable value of the electron emission current is set (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: switch PARAMETERS, from the ISOL position. should be set to position Ia, and the INSULATION switch from position KN to position PAR. and with the MEASUREMENT button pressed, read the value of the anode voltage using the arrow indicator. After that, the INSULATION switch must be set to the KN position again. The duration of the measurement in this case (the time from the moment the INSULATION switch is switched from the KH position to the PAR. position and back) should not exceed 5 s.
To check gas-filled zener diodes, you need:
Set the INSULATION switch to PAR. and the PARAMETERS switch to UA.
By pressing the MEASUREMENT button, smoothly apply voltage to the lamp with the potentiometer knob Ua until it is ignited and, using the indicator of the device, fix the ignition voltage.
Switch the PARAMETERS switch to position Ia and use the potentiometer knob UA to set the minimum and maximum current values indicated on the test card.
At extreme current values, set the PARAMETERS switch back to position Ua and read off the value of the combustion voltage.
The change in the stabilization voltage is determined by the difference between the voltages of the go-
rhenium measured at the maximum and minimum currents, minus 1 V (voltage drop across the shunt of the milliammeter 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 must:
1. Having prepared the device for operation, set the INSULATION switch to 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 the position 1xv and read the current strength according to the arrow indicator of the device.
If you set a certain value of the anode current indicated on the test card or in the specifications for the lamp, then you can measure the blocking voltage of the first grid by moving the PARAMETERS switch to the Uci position.
When characterizing lamps, you must be guided by the following:
1. For characterization, use key test card No. 1, on which all 144 holes are punched on the plug-in switch, indicating the numbers and purpose of the holes. The holes on the map are divided into two groups: upper (I) and lower (II). The holes of each group are labeled from 1 to 72 inclusive. In the future, the number of each hole will be denoted by a fraction, the numerator of which shows the number of the hole, the denominator - the number of the group. For example, hole 2/1 indicates the second hole of the upper group, hole 1/II - the first hole of the lower group.
Before characterization, set the GLOW, Uci, Ua and Uc2 knobs to the left extreme position (counterclockwise). Then, having applied a key card to the test card for a given type of lamp under test and having determined through 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 the numbers of holes that need to be filled with switching plugs according to the circuit diagram of the device.
Insert the lamp under test into the appropriate panel of the instrument, bearing in mind that
to supply the voltages of the glow (15 V), the first grid (75 V), the second grid (300 V) and the anode (300 V), plugs are not required to be inserted into the switch. It is forbidden to simultaneously fill with plugs two holes of the same voltage, the same current and slope on the switch.
The supply of voltage to the lamp under test begins with incandescence, for which, starting from hole 22/P, which corresponds to the minimum filament voltage, it is necessary to sequentially rearrange the switching plug into the following holes until the required filament voltage is set with the GLOW knobs (GROUGH and SMOOTHLY) . To connect a pointer indicator to a filament voltage source when the filament is powered by 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.
The bias voltage is applied to the first grid of the lamp under test up to -10 V by filling holes 2/1 with a plug, up to -65 V - holes 1/1; smooth adjustment of the bias voltage is made with the Uci knobs labeled -10 and -65.
When testing all types of lamps, except for gas-filled zener diodes, a breakout plug must be inserted into hole 12/P in order to short-circuit the ballast resistor R56 in the anode circuit of the lamp.
To supply a constant anode voltage to the test lamp, it is necessary to fill the holes 25/1, 46/P and 58/11 with plugs (with the Ua knob, the voltage can be changed within 15 ... 140 V); holes 26/1, 52/P and 40/11, if the anode voltage needs to be regulated within 140 ... 300 V.
A constant voltage is applied to the second grid of the lamp under test within 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 adjustment of the voltage on the second grid is carried out with the Uc2 knob.
If the voltage at the anode of the lamp under test must be greater than 140 V, and the voltage on the second grid must 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 must be less than or equal to 140 V, and the voltage on the second grid must be greater 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 measuring 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 a 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 forbidden to simultaneously fill with plugs any two or more holes within 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 tested lamp of interest is taken 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 must be set to the Uci position) and fix the change in the anode current of the lamp (the PARAMETERS switch is set to position 1a).
Semiconductor testing
One of the main electrical parameters by which semiconductor diodes are rejected is the reverse current of diodes I arr 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 in the case when, during the measurement, the parameters do not fit within certain limits. For example, if the current I k. o exceeds the maximum guaranteed limit for a given type of transistor by more than 2 ... 3 times or continuously increases with time, then such a transistor is unsuitable for use. Transistors are also rejected, in which β \u003d 5 ... 8 or less.
When measuring the parameters of semiconductor devices, the integrity of their electron-hole transitions is checked.