If you doubt the validity of a diode, transistor or want to determine their conductivity type, use one of the devices with which we introduce you in this article. The advantage of the devices is simplicity: they can even build a new ham. The basic design is based on schematics from the Bulgarian journal “Radio television electronics”.
The scheme is a very simple device in figure 1. If the diode is connected to the terminals X1, x2, serviceable — the lamp H1 or H2 in accordance with its type of conductivity: n—p—n or p—n—p. If you burn both of the pampas, the diode is broken. On the contrary, none of them will light up if the test diode has an internal open.
Since the transistor can imagine about the form of two series-connected diodes (Fig. 2) using “that tool you can test and semiconductor triodes. In this case, each transistor experiencing twice; to terminals X1, x2 at the beginning connect the findings of the collector and the base, then the base and emitter.
The device is applied to flat Pampa 10 X 50 mA. The supplied low voltage for 6.3 V is allowed to reduce the current through the lamp to 30 mA. But it did not eliminate the main drawback of the device: they do not test a low-power diodes and transistors, the allowable current less than 30 mA.
This lack is not in the device, whose scheme is in figure 3. The current flowing through the test diode is less than 1 mA (through the use of a current amplifier transistors V2 and V6).
The transistors are easier to scan with the device assembled according to the scheme shown in figure 4. The test transistor included in the amplifier stage, operating in the mode of class D.
Fig. 1.
Fig. 2.
Fig. 3.
Fig. 4.
Fig. 5.
If the indicator lamps do not burn, so the transistor is not broken. With the closure of the S1 button on the base current is supplied through the resistor R1, and the transistor opens. The LEDs H1 and H2 corresponding to the type of conductivity. No signal indicates either an internal open or a very small gain.
The device allows you to check diodes and transistors, the maximum current is not greater than 30 mA. If the allowable current of the transistor is more than 300 mA, as a tracer used pampas 6.3 In X 0.28 A. Depot that the initial collector current from the power transistors can be more than 20 mA. In this case, the low voltage indicator of the pampas will glow, and when open the switch S1, while the transistor is OK.
Diagram of the universal device, designed for any diodes and transistors, ka is shown in figure 5. Button S2 is pressed when checking the power transistors. SIC transistors V2, VЗ and V6, V7 allows to be used as a conventional indicator of the pampas 6.3 ВХ0,28 A. Transistors V2, V7 ГТ402 with any alphabetic index, П201— П203, П213—П217.
Step-down transformer T1 in all schemas assembled on an iron core mm. 11120X20 Network winding for voltage 127 V contains 1600, and 220 — 2750 turns of wire sew-2 0,1—0,12. The secondary winding has 79 turns of wire PEV-2 of 0.51.
E. TARASOV, engineer
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