With an Open applied to channel A (nothing connected to A and COM test plug), adjust the VERT (vertical) control until the horizontal trace is as close to even with the horizontal axis as possible. Once set, these adjustments should not need readjusting during the unit's operation. However, remember that each time the unit is used, this process will need to be accomplished.

Range Selection

Four impedance ranges (LOW, MED 1, MED 2, and HIGH) can be selected on the Tracker 2000. These ranges will become active when the appropriate front-panel button is pressed. To obtain the most useful signature display when troubleshooting a component, you should always start by selecting one of the two medium ranges (medium 1 or medium 2). If the display appears to be an open (horizontal trace), then the next higher range should be selected to get a more accurate signature for analysis. If the display appears to be a short (vertical trace), then the next lower range should be selected.

The AUTO feature, when selected, will allow the unit to automatically scan through the four ranges at a speed set by the technician using the RATE control knob. This allows the user to keep his or her hands free to hold test leads while still being able to observe the component under test signature for analysis. The HIGH LOCKOUT, when selected by the technician, prevents the unit from functioning in the HIGH range in either the manual or AUTO mode.

Channel Selection

You can select two channels by pressing the channel A (test probes connected to A jack and COM) or channel B (test probes connected to B and COM jacks) push button on the front panel. When using a single channel, you should plug the red probe into the corresponding channel test jack, and plug the black test lead into the common test jack. When testing a component, you should connect the red probe to the positive terminal and the black probe to the negative terminal of the component under test. Following this procedure every time will ensure that the signature for the component under test will be displayed in the correct quadrants of the CRT display.

The ALT (alternate) mode provides automatic switching back and forth between channel A and channel B. This allows you to easily compare two components or the same test points on two circuit boards. You select the ALT mode by pressing the ALT push button on the front panel. The rate of switching between channels A and B can be varied by adjusting the RATE control knob on the front panel. You will find that the ALT mode feature is very useful for comparing a known good component with the same type of component that is of unknown quality.

Figure 5-21 shows a typical way of connecting the unit to a known good circuit board and a board under test. This test mode uses the supplied common test leads to connect two equivalent points on the boards to the common test jack. Note that the black probe is now being used in the channel B jack rather than the COM jack. When the technician uses the ALT and AUTO features together, each channel is displayed before the range selection will change. Figure 5-22 shows the sequence of these changes.

Figure 5-21. - ALT (alternate) mode setup.

Figure 5-22. - AUTO/ALT sequence.

Frequency Selection

There are three test signal frequencies (50/60 Hz, 400 Hz, and 2000 Hz) that can be selected and then provided by pressing the appropriate front-panel push button. During most troubleshooting evolutions, the 50/60 Hz test signal is the best to start with. The 400 Hz and 2000 hz frequencies are generally used to view small amounts of capacitance or large amounts of inductance.

Pulse Generator

A built-in pulse generator is also provided with the Tracker 2000. It allows the technician to do dynamic, in-circuit testing of certain devices in their active mode. In addition to using the red and black probes, you can connect the output of the pulse generator to the control input of the device to be tested with one of the blue micro clips provided with the unit. The pulse generator has two outputs (G1 and G2 jacks) so that three devices can also be tested in the ALT (alternate) mode. Figure 5-23 shows a way of connecting the unit in the ALT mode using the pulse generator.

Figure 5-23. - Pulse generator comparison mode.

There are a variety of output waveforms available using the pulse generator selection buttons, as shown in figure 5-24. First, the technician must select the PULSE mode or DC mode using the PULSE/DC button located on the front panel. In the PULSE mode, the PULSE/DC LED flashes at a slow rate. While in the DC mode, this LED will be continuously on.

Figure 5-24. - Pulse generator selector chart.

Next, the technician needs to select the polarity of the output desired by using the positive (+) and/or negative (-) push buttons. All three buttons only function in a push-on/push-off mode and will only interact with each other to avoid the NOT ALLOWED state found in figure 5-24.

Once the specific output type has been selected, the output desired by the technician is set using the LEVEL and WIDTH controls. The LEVEL control is used to vary the magnitude of the output amplitude from zero to 5 volts (peak or DC). During the PULSE mode, the WIDTH control will adjust the cycle of the pulse output from low to 50 percent maximum (square wave).

The start of a pulse will be triggered by the appropriate zero crossing of the test signal, which results in the pulse frequency being equal to the selected test signal frequency.

The end of the pulse is determined by the WIDTH control setting, which determines the cycle length. The WIDTH control, however, has no effect when the DC mode is selected.

FUNCTIONAL OVERVIEW

There are six major sections in the Tracker 2000, as shown in the block diagram in figure 5-25. The control logic section controls the selection of the channel, frequency, impedance range, and pulse generator mode according to the front-panel buttons pushed by the technician. The oscillator provides the test signal that is used by the signal and pulse generator sections. In the signal section, the test jacks are driven by the test signal, while signal conditioners monitor the jacks and produce the horizontal and vertical signals used by the CRT section to produce a component signature on the display. The pulse generator provides an added source for testing three additional terminal devices. The power supply produces all the required voltages needed to operate the Tracker 2000.

Figure 5-25. - Tracker 2000 block diagram.