Author: Wang Shaohua
Friends engaged in home appliance repair, there is always a transistor with a transistor pressure tester, used to check the back pressure (withstand voltage) value of the transistor, the voltage regulator value of the regulator, even the leakage current of the capacitor, the size of the motor windings, etc. . This article introduces you two transistor withstand voltage testers. These two testers have the advantages of easy production, easy to make, and easy to carry. The above figure is a pressure test instrument for transformer production using a 14-inch black and white TV full line (many friends have ready-made, and can also be separated). In the figure, Q1, Q2 constitute a self-excited multi-resmium. When the K is pressed, the oscillator starts oscillating, and the internal output transformer boosts the internal silicon rectifier, and the C2 filter is output, and the voltage is output (which can meet the measurement output tube requirements), and then the R2 is added to the test end. The test end can be introduced by an insulated wire, and the black two crocodile clips will be clamped by the measured component. The range of voltmeter V is 1500V, which needs to be restructured. A normal 300V voltmeter or other range of quotations can be made to the terminal restriction resistance, see the middle.
Before the production, use a high sensitivity multimeter RX10K block or the bridge to measure the internal resistance, assuming to RV, then follow the resistance of 4 1 W resistance and RV, respectively, respectively, respectively, respectively, the four electrical resistance welded single knife Four throw switches on the joint head. If the voltage meter is 300V range, the contact position of the rotating K can obtain different ranges of the voltage meter, and below 1500V, 1200V, 900V, 600V, 300V, respectively, 500V, respectively. A jack (available copper rivet nails on the insulating plate) in the upper end of the voltmeter is used to insert a hard-purpose table pen pen, when it is necessary to detect a crystal reverse voltage value or a regulator tube voltage regulator value of the lower counter voltage value, pressure When the pressure sensitive value of the sensitive resistance, if the DC voltage gear (range from 5V ~ 500V) is used in the multimeter, the more accurate measurement can be obtained.
Component Numerical See the figure in the figure. The β value of Q1 and Q2 is greater than 100. The C1 is high with high voltage regulatory properties, and the amount of polypropylene compressions having a small loss can be selected from 0.001 to 0.0033 μF. C2 can be used with 5 2.2 μF400V withstand voltage polypropylene. R1 is solid-adjustable with 100KΩ small. After the K is closed, the adjustment R1 gradually decreases from the maximum, and the circuit can not be adjusted after the circuit starts forth.), Then the 氖 bubble should be lit (it actually does a high-voltage signal lamp function, can also do not want). If you can't start, the transformer primary winding joint header can be changed, check whether the line is getting wrong, check if C1 is poor, and then try again. K with a small button switch.
Be careful before use should be used with a crocodile clip, the voltage meter is placed at the highest voltage gear, and then the switch can be pressed.
If the voltage meter reads are small, the range is too large (the voltage resistance value of the measurement element is too small) or the leakage is severe, and even breakdown, the range can be reduced until the low voltage is measured. If the motor winding is the insulation resistance of the casing, the crocodile clip should be sandwiched between the winding terminal and the outer casing. The higher the voltage meter reading, indicating that the degree of insulation is, if this time the multimeter current barrier strips into the outer casing Between the crocodile clips, a leakage current can also be measured. vice versa. If the voltage meter reading is zero, the winding has been collining (short circuit with the housing).
The picture below shows a pressurizing tester after 2 multiplier rectification directly 220V, and the 220V voltage is introduced by two pin power plugs, and the output (no load) voltage is about 600V. Related component specifications are shown in the figure. Since the value of C1 and C2 is small, the test end short circuit current is less than 1mA, even if the test end element is shorted, the power supply does not affect the power supply, so there is no limit resistance.
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