Tektronix 1S1 Instruction Manual page 91

Calibration – Type 1S1
Fig. 5-31, Typical indicator oscilloscope displays for setting
up 2-trace display and checking loop gain.
u. Check for a waveform similar to that shown in Fig.
5-31C). The line at the base should be at the same level as
the baseline of the pulse.
v. If the loop gain waveform is not correct:
1. Check the adjustment of R95 (MEMORY GATE
WIDTH) by turning the control slightly each way from its
original position and observing the change in the wave-
form. See Fig. 5-33 for the location of R95.
2. Adjust R95 to the point of maximum gain (see Fig.
5-32A-C). Maximum gain is observed as the greatest
separation between the two displayed traces.
3. Adjust C135 to set the loop gain at unity (gain of
5-28
1). This is indicated by a straight-line display of the lower
trace (see Fig. 5-32B).
w. Set the pretrigger pulse generator Output Polarity
switch to -
x. Set the Type 1S1 TRIGGER SOURCE switch to INT-
y. Check for a waveform indicating unity loop gain. The
2-trace separation should not change by more than 0.2 cm,
as compared to the display with +polarity.
z. Set the pretrigger pulse generator Output Polarity
switch back to +.
aa. Set the Type 1S1 TRIGGER SOURCE switch to INT+.
Fig. 5-32. Typical indicator oscilloscope displays for adjusting
loop gain of Type 1S1.