Quantcast Testing Components by Comparison

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The Huntron Tracker 2000 has the following features:

  • Multiple-test signal frequencies (2000 Hz, 400 Hz, and 50/60 Hz).
  • Four impedance ranges (low, medium 1, medium 2, high).
  • Automatic range scanning.
  • Range control: High Lockout.
  • Rate-of-channel alteration and/or range scanning is/are adjustable.
  • Dual-polarity pulse generator for dynamic testing of three terminal devices.
  • LED indicators for all functions.
  • Dual-channel capability for easy comparison.
  • Large CRT display with easy-to-operate controls.

The device to be tested must have all power turned off, and have all high voltage capacitors discharged before connecting the Tracker 2000 to the device.

Testing Components by Comparison

Testing components by comparison is the most preferred method for troubleshooting. The ALT (alternate) mode setup is the most commonly used mode for this method. This mode allows the technician to compare a known good component to a suspect component. This is accomplished by connecting channel A to a known good device, channel B to the device under test, and a common test lead to COM as illustrated in figure 2 - 34. Select the ALT button, and the 2000 will alternately display the signature of the known good device and the device under test. By examining the signature differences, you can detect a defective component. Figure 2 - 35 is a typical example of the CRT display on the 2000 while testing the base to emitter on a good transistor. Figure 2 - 36 illustrates a defective transistor under the same test setup. Note that in the low range, the transistor appears to be good. Sometimes component defects are more obvious in one range than another, so is a suspect device appears normal for one range, try the other ranges.

Figure 2 - 34. - Alternate mode setup.

Figure 2 - 35. - Signatures between base-emitter of a good transistor

Figure 2 - 36. - Signatures between base-emitter of a defective transistor.

Q.31 What is the most preferred method of troubleshooting?answer.gif (214 bytes)
Q.32 Why is it recommended to use more than one range while troubleshooting a device? answer.gif (214 bytes)

Troubleshooting Tips

When you are testing individual components in a circuit, a parallel resistor or diode of similar value may cause a defective component to appear good. Therefore, you should, in most cases, electrically isolate the suspected component from the circuit while testing individual components. The best way to do this is to desolder all but one lead on the suspected component.

Q.33 When you are testing individual components in a circuit, what may cause a defective component to appear good? answer.gif (214 bytes)

You should be aware that devices made by different manufacturers may appear to have slightly different signatures. This is normal, especially with digital integrated circuits, and does not necessarily indicate a failed device. When this occurs, the best way to verify this is to compare the outputs of the device under test with the equipment specifications to ensure the signals are adequate for proper equipment operation.

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