Oscillator Troubleshooting Checklist

Chapter Oscillator Troubleshooting Checklist

Complete Electronics Self Teaching Guide with Projects
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Complete Electronics Self Teaching Guide with Projects

  • CHAPTER 9 OSCILLATORS426QUESTIONWhat is the value of CB? ANSWERC0.1 FB5m 30  Continue the design procedure steps.10. After you build an oscillator, apply power to the circuit and look at the output sig-nal on an oscilloscope. If the output signal is oscillating, check the frequency. If the frequency varies significantly from the desired frequency, then change C1 until you get the wanted frequency. Change C2 to keep the ratio of the capacitance val-ues about the same as discussed in step 5. C2 affects the output level.11. If the circuit does not oscillate, go through the steps outlined in the troubleshoot-ing checklist that follows.OSCILLATOR TROUBLESHOOTING CHECKLISTIf an oscillator does not work, most often the trouble is with the feedback connections. A little experimenting (as outlined in steps 2 through 6 of the following checklist) should produce the right results. This is especially true when you use an unknown coil that may have several taps or windings. However, you should try each of the following steps if you have trouble.1. Ensure that CB, CC, and CE are all large enough to have a reactance value less than 160 ohms. Ensure that CE is less than one-tenth of RE.2. Check the C1/C2 ratio. It should be between 3:1 and 10:1.3. Swap out C1 and C2. They may be connected to the wrong end of the LC circuit.4. Check that you made the feedback connection to and from the correct place.5. Check both ends of the LC circuit to see that they are connected to the correct place.Book Author c09 V1 07/04/2012 3:23 PM c09.indd 4267/4/2012 3:24:52 PM