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The electrical schematic of this tester is shown in Figure 1. Mainly test the following five types of components: 
Figure 1 Tester circuit schematic
1. Current source component; 2. Precision reference voltage source; 3. Adjustable positive and negative voltage output integrated voltage regulator; 4. Fixed positive voltage output integrated voltage regulator; 5. Fixed negative voltage output integrated voltage regulator Wait.
The equivalent circuit diagram for testing various types of commonly used components is shown in Figure 2.
Figure 2a shows the test schematic of the three-terminal adjustable current source LMl34/234/334. To simplify the test line. Easy to use common resistors. The current test of the adjustable current source is converted to a test similar to the LM317 adjustable integrated regulator reference voltage Vref. At room temperature, the set current in Figure 1 is about 8.3mA, which can be used as the minimum load current for LM317 and 337 tests. At this time, the voltage drop across the R2 (150Q) resistor is about 1.25V. If the voltage measured by the digital multimeter is around 1.25V and the reading of the output voltage of the regulated power supply is unchanged, the component is good.
Figure 2b, c, d, and e are test schematic diagrams of various precision reference voltage sources. Among them: LM335's reference voltage is about 2.98V; LM336's reference voltage is about 2.49V; LM385's reference voltage is 1.25V and 2.5V; TL431's reference voltage is about 2.5V, and TLV431's reference voltage is 1.25 V or so.
Figure 2f shows the test schematic of the LM317 adjustable positive voltage output integrated regulator. Its reference voltage Vref is around 1.25V. The minimum load current during the test is around 8.3 mA. It meets the requirements for minimum load current during normal operation.
Figure 2g shows the test schematic of the LM337 adjustable negative voltage output integrated regulator. The reference voltage Vref is around -1.25V, and the minimum load current is also about 8.3mA.
Figure 2h is a test schematic diagram of the LM337L. The 2 and 3 pins are exactly opposite to the LM337 pins.
Figure 2i shows the test schematic of the LM78xx fixed positive voltage output integrated regulator. Among them, XX is the regulated voltage output of the device, and has various voltages such as 5V, 6V, 8V, 9V, 12V, 15V, 18V, 24V.
Figure 2j shows the test schematic of the LM78Lxx fixed positive voltage output regulator. The 3 and 1 pins are exactly opposite to the pins of the LM78xx.
Figure 2k shows the test schematic of the LM79xx fixed negative voltage output integrated regulator. There is also a variety of negative output voltages from 5V to a 24V.
The circuit of the tester in Figure 1 is very simple, similar to the line of a general multimeter. However, only three resistors and two capacitors are used. In the figure, K1-1~K1-4 adopts a double-layer, double-pole and five-position band switch for selecting the type of test device. Among them: 1st gear is adjustable current source test RIV, such as LM334; 2nd gear is precision reference voltage source test block, such as: fixed LM335, LM336, LM385 and adjustable TL431; 3rd gear is adjustable positive and negative voltage Output integrated regulator test block, such as LM31 7, LM350, LM337, etc.; 4th gear is fixed positive voltage output integrated regulator test file, such as LM78xx series; 5th gear is fixed negative voltage output integrated voltage regulator test block, Such as LM79xx series. BG is an external 0-30V adjustable regulated power supply. K2-1-K2-2 is a double-pole double-throw switch for switching the polarity of the power supply during positive and negative voltage output. AN is the button.
The voltage parameters of various components can be read by pressing the button during the test. The test results are displayed using an external digital multimeter. When the reading is negative, the component under test is an integrated voltage regulator with a negative voltage output.
The pin socket uses an 8-pin integrated circuit socket. The above four rows of jacks are mainly used to measure components with positive voltage output, such as 1, 2, 4 and 3 LM317 components (individual negative voltage output components. Also included here is LM337L).
The tube socket number of the row is marked with P, for example, P?2 3 4. The pin 1-2-3 of the component is inserted into the 2-3-4 jack of the positive voltage output P-row socket. A row of four jacks under the header is used to measure the adjustable and fixed integrated regulators for negative voltage outputs, such as the LM337 and LM79xx. The socket jack number is marked with N in front. For example, N-1-2-3 means that the 1-2-3 pin of the component is inserted into the 1-2-3 jack of the negative voltage output N-row socket. The C1 and C2 capacitors are stable. Prevent oscillations.
Measurement methods
1. Connect the external regulated power supply and digital multimeter to the tester. 2. Dial the type selection switch K1-1~K1-4 to the required gear according to the type of test component. See Table 1 for details. 3. Test The pin number of the component is defined as the front side with the word being the front side, and the pin is programmed from the left to the right as 1, 2, 3. The component is used in a common three-terminal integrated voltage regulator and the reference voltage current source tester operation. The pin is inserted in the corresponding socket of the socket in the attached table; 4. According to the need, the polarity switching switch K2 of the regulated power supply output is turned to the positive or reverse connection position, and the power supply in Fig. 1 is in the positive connection state; The button reads the result of the measurement from the digital multimeter. Good components should read between the maximum and minimum values in the component manual and change the output voltage of the regulated power supply (must be adjusted between the minimum and maximum input voltages of such components). change.
The detailed test operation of various commonly used components is shown in Table 1. If abnormal conditions occur during measurement, the AN button should be released quickly. Such as: reading deviation is very large, the power supply current limit protection action. The component is generally bad if the inspection operation is correct and the reading remains the same.
Due to the large number of manufacturers of integrated voltage regulators and various reference voltage current source devices, there are many corresponding models and packages; new components are constantly being developed. Such as low voltage difference integrated regulators, etc., therefore. Only the common model operation methods are listed in the table. Other types and models of components (including integrated sensors, etc.) can be used according to the principle and manual. Components for the TO-3 package. A self-made replacement socket connector for testing.
The tester has simple circuit, low cost, easy production and convenient testing. And the types and types of test components are numerous, and the test data can provide a basis for the design of electronic circuits.
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