Tektronix 485, Instruction Manual

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Calibration—485/R485 Service
d. Set A TRIGGER HOLDOFF to max; test oscillo­
scope to 1 V/div (10 V/div at probe tip) and connect 10X
test probe to Z OUT DC test point.
e. Set INTENSITY for 50 V step.
f. Connect the DVM to the AUTO FOC test point.
Measure and record the DC voltage.
g. Observe the 485 display and adjust FOC GAIN
(R1710) for optimum focus. If the original setting cannot
be improved, reset FOC GAIN to the voltage recorded in
step f and continue to step 13.
h. If focus was improved by adjusting FOC GAIN,
preset MAX Z (R1560) CW and MAX FOC (R1700) CW.
i. Set A TRIGGER HOLDOFF to NORM.
j. Set FOCUS and ASTIG for optimum focus at low
display intensity.
k. Set A TRIGGER HOLDOFF to max and adjust
INTENSITY for a 70 V step at Z OUT DC test point.
l
. Adjust FOC GAIN for best focus.
m. Record the new DC voltage at the AUTO FOC test
point.
n. Turn INTENSITY to max and adjust MAX Z
(R1560) for a 72 V step on the test oscilloscope.
o. Set MAX FOC for the voltage recorded in step 12m.
p. Set A TRIGGER HOLDOFF to NORM.
1 4 . CHECK O U TPU T W A V E FO R M S (With
Sweeps Running at 1 ms/div)
a. With test oscilloscope check the following outputs
(located on the rear panel).
b. A and B GATES, approximate amplitude 4 V; 0.5 V
into 50 £2.
c. A SAWTOOTH, approximate amplitude 10 V; 0.5 V
into 50 O.
15. ADJUST TRACE R O T A T IO N
a. Position trace to graticule center.
b. Adjust TRACE ROTATION (rear panel) so trace
parallels center graticule line.
16. ADJUST Y A X IS A L IG N M E N T
a. Apply 1 ms and 0.1 ms markers of full screen
amplitude to CH 1.
b. Set TIM E/D IV to 1 ms.
c. Adjust A VARIABLE TIM E/D IV for two markers per
div.
d. Adjust Y AXIS (R1794), located towards rear of B
Trigger board, for vertical alignment at the graticule center.
17. ADJUST G EO M ETR Y
Adjust GEOM, (R1792), located towards rear of B
Trigger board, for least bowing of the vertical lines at the
graticule edges.
18. ADJUST H O R IZ O N T A L G A IN
a. Set HORIZ DISPLAY to B; TIM E/D IV to 0.1 ms/div,
A VARIABLE TIM E/D IV to CAL.
b. Apply 0.1 ms markers.
c. Use POSITION (HORIZ) control to keep markers
aligned with graticule lines.
d. Adjust H GAIN (R1366), upper rear of Sweep board,
for one marker/div and for exact alignment of markers at 1
and 9 (center 8 divisions).
19. ADJUST A SWEEP CAL
a. Set HORIZ DISPLAY to A.
b. Use POSITION (HORIZ) control to keep markers
aligned with graticule lines.
REV. B, SEPT. 1974
5-11