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Performance Tests
TDS 684A, TDS 744A, & TDS 784A Service Manual
4–39
2. Confirm all four channels (CH 1 through CH 4) are within limits for channel
delay:
a. Set up the generator: Set the generator frequency to 250 MHz and the
amplitude for about six divisions in CH 1.
Hint: As you are adjusting the generator amplitude, push SET LEVEL
TO 50% frequently to speed up the updating of the waveform amplitude
on screen.
b. The horizontal SCALE should already be set to 500 ps. On the TDS
784A, now set it to 200 ps. On the TDS 744A, push the front-panel
ZOOM button, press the side-menu On button, set the horizontal
SCALE to 250 ps, and be sure the vertical scale factor is kept at 1.0X
and the horizontal scale factor is 2.0X.
c. Save a CH 2 waveform: Press CH 2. Be sure the vertical scale factor is
kept at 1.0X. Then press save/recall WAVEFORM. Now, press the
main-menu button Save Wfm; then press the side-menu button
To Ref 2.
d. Save CH 3 waveform:
H Move the coupler from CH 2 to CH 3, so that CH 1 and CH 3 are
driven. Press WAVEFORM OFF. Press CH 3. Be sure the vertical
scale factor is kept at 1.0X. Then press the side-menu button
To Ref 3.
e. Display all test signals:
H Press WAVEFORM OFF to remove CH 3 from the display.
H Display the live waveform. Move the coupler from CH 3 to CH 4,
so that CH 1 and CH 4 are driven. Press CH 4 to display. Be sure
the vertical scale factor is kept at 1.0X. See Figure 4–10 on page
4–40.
H Display the reference waveforms. To do this, press the front-panel
button MORE. Press the main-menu buttons Ref 2 and Ref 3. You
may notice their overlapping ground reference indicators. See Figure
4–10 on page 4–40.
f. Measure the test signal:
H Locate the time reference points for these waveforms. Do this by
first identifying the point where the rising edge of the left-most
waveform crosses the center horizontal graticule line. Next, note the
corresponding time reference point for the right-most waveform. See
Figure 4–10 on page 4–40.
H Press CURSOR.