Tektronix TDS 420A, Service Manual, Page: 100 / 288

Performance Tests
4- 32
TDS 420A, TDS 430A & TDS 460A Service Manual
c. If you are testing a TDS 430A, skip to step h.
d.
Save a CH 3 waveform:
Move the coupler from CH 2 to CH 3 , so that
CH 1 and CH 3 are driven. Press CH 3 ; then press the side-menu button
To Ref 3
.
e. Display all test signals:
H
Press WAVEFORM OFF twice to remove CH 2 and CH 3 from
the display.
H
Move the coupler from
CH 3
to
CH 4
, so that CH 1 and CH 4 are
driven. Press CH 4 to display.
H
Now, press the front-panel button MORE . Press the main-menu
buttons Ref 2 and Ref 3 .
f. Measure the test signal:
H
Locate the point on the rising edge of the left-most waveform where
it crosses the center horizontal graticule line. This is the
time
reference point for this waveform. Note the corresponding time
reference point for the right-most waveform. See Figure 4--9.
H
Press CURSOR ; then press the side-menu button V Bars .
H
Press CLEAR MENU .
H
Rotate the General Purpose knob to align one cursor to the time
reference point of the left-most waveform edge and the other cursor
to the time reference point of the right-most waveform edge. (Press
SELECT to switch between the two cursors.) See Figure 4--9.
H
Read the measurement results at the
∆
: cursor readout, not the @:
readout on screen.
g. Check all channels against limit: CHECK that the cursor readout on
screen is
≤
450 ps. If the cursor readout is
≤
200 ps, skip substep h.