The Importance of Electronic Troubleshooting

5-17). In contrast, when the polarity of the ability source is oppositiond, the rectifying tube is said to be "back prejudice" (Olesky, 1992, pp. 5-17). Below certain potencys, the back biased diode lead not conduct.

Half-wave rectifiers containing diodes produce a pulsatile load voltage. This results from the fact that diodes only(prenominal) conduct when they are forward biased (i.e., only during unmatchable phase of the alternating current cycle). This pulsatory effect whitethorn be smoothed out, however, by incorporating gain vigor capacitors into rectifier circuits. During diode conduction, such capacitors frivol away to approximately the peak input voltage. They then discharge when the diode is nonconducting. This mechanism maintains a "nearly constant voltage crosswise the load" (Olesky, 1992, pp. 5-17).

In addition to diodes and capacitors, unregulated power supplies may also incorporate transformers. A typical iron kernel transformer consists of primary and auxiliary insulated windings wrapped around a laminated core's promenade post. The voltage produced in the secondary winding depends on the go of turns of wire on both the secondary and primary windings. The secondary winding voltage may be higher or lower than that of the primary winding.

Further modifications to unregulated circuits include the full-wave rectifier, the full-wave bridge, and the voltage doubler. For unity, full-wave rectifiers generally contain 2 diodes and a center-tapped transformer. The 2 diodes change state alte

Defective transistors can be located using either an in-circuit transistor checker or an ohmmeter. With the in-circuit transistor checker, testing merely involves connecting the tester's leash clips to the suspect transistor's three terminals. In contrast, ohmmeter checking is more involved. For example, one step in the motion involves measuring "a low opposition in one direction across the base-emitter diode and a high resistance when the leads are overturnd" (Olesky, 1992, pp. 135-154). This usually indicates that the junction is functioning properly. Second, connatural measurements should be obtained at the collector-base junction. Third, a functional collector-emitter junction give show high resistance in both directions.

disregardless of which type of test equipment is apply to evaluate transistors, however, the components should be retested ensuant to removal. Sometimes, parallel transistors within a circuit can regulate test observations (Olesky, 1992, pp. 135-154).

Electronic troubleshooting may also be employ to regulated power supplies. Because of internal resistance, the terminal voltage of a power supply may vary according to changes in current drain. In certain circuits (e.g., test instruments or estimator circuits) this can cause significant problems. One component that is used to regulate voltage is the zener diode. At applied voltages greater than its sectionalization voltage, the back biased zener diode maintains a constant voltage.

characteristic problems that occur with regulated power supplies include opens and shorts within the diodes. In addition, zener diodes don't function properly at low reverse voltages. Furthermore, zener diodes can be destroyed by high reverse voltages.

Similarly, an ohmmeter can be used to evaluate faulty filter capacitors. Leaky capacitors exhibit characteristics resembling "low resistance shunting" (Olesky, 1992, pp. 17-21). As the capacitor becomes charged, however, the ohmmeter's needle will gradually
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