Tektronix 7623, Instruction Manual

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Calibration —7623/R7623 Service
h. Remove transistor O1788.
i. Press ERASE button.
j. CHECK -Storage test points (see Fig. 2-10). Table 2-5
lists the storage test points and their voltage tolerance.
Connect the test oscilloscope 10X probe to each storage
test point, in turn, setting the test oscilloscope vertical
deflection to 1.0 V, 2.0 V, and 5.0 V as required.
TABLE 2-5
Test Point Tolerance
Bi-Stable Approximately 320 V
CE, +81.6 V to +88.4 V
FGA
+86.4 V to +93.6 V
k. Install transistor Q1 788.
l. Press the ERASE button.
m. Check that the storage screen erases.
n. Connect the 10X probe to the bi-stable test point.
Set test oscilloscope vertical deflection to 5 volts/division at
a sweep rate of 0.2 second/division.
Fig. 2-11(A). Erase waveform (Bi-stable Test Point), (B). Transfer
waveform (High speed test point).
o. Press the ERASE button.
p. CHECK — lest oscilloscope display for an erase wave­
form (see Fig. 2-11 ).
43. Adjust Bi-Stable Operating Level
a. Connect the low-frequency sine-wave generator to the
left vertical amplifier plug-in unit.
b. Set the frequency of the sine-wave generator for a
three kilohertz signal at 3.2 divisions of vertical deflection.
c. Set the horizontal time-base plug-in unit for a sweep
rate of 0.1 millisecond/division.
e. Find lower writing threshold; adjust R1325 toward
the zero volt level until the storage screen starts to go dark
(see Fig. 2-10 for location of adjustments).
f. Find upper writing threshold; adjust R1325 until the
stored signal level just fades into the background level.
g. Adjust Bi-Stable Op level mid-way between the lower
threshold level and the upper threshold level.
h. Connect the test oscilloscope 10X probe to the FGK
test point.
i. Press the INTEG button.
d. Press the AUTO ERASE button (in), and turn the
AUTO VIEWTIME control fully clockwise.
j. CHECK —That the FGK voltage increase to approxi­
mately +50 volts.
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