Tektronix 485 User Manual

Calibration—485/R485 Service
a. Set SWEEP MODE to AUTO TRIG.
b. With vertical POSITION control center the trace.
a. Set TIME/DIV to 0.1 ps; HORIZ DISPLAY to A, and
VERT MODE to CH 1 (make sure SWEEP MODE is in
AUTO TRIGGER).
b. Set test oscilloscope to 0.05ps/div and 0.1 volt/div.
c. With DVM measure the two vertical deflection plate
voltages at the CRT neck pins fed from the output of
U660. (May need 1 kS2 resistor in series with the test leads
to prevent vertical oscillations.)
c. Connect 10X probe (1 V/div at probe tip) to Z OUT
HF test point.
d. Adjust INTENSITY for 4 div of signal.
d. Calculate the average of two voltages.
e. Check aberrations for 2% or less.
e. Connect DVM to COMP PL test point located next to
the COMP PL potentiometer at rear of Horizontal Amp
board.
f. If necessary adjust Z COMP (Cl 762, Cl 765, and
R1865).
f. Check for the calculated voltage, ±0.3 V.
g. Check Z AXIS RISETIME for 15 ns or less.
g. If necessary adjust COMP PL (R1796).
12. CHECK EXT Z AXIS BLANKING
10. ADJUST GRID BIAS
a. Apply 0.2 V P-P of 20 MHz from Type 191 Signal
Generator to EXT Z AXIS blanking (rear panel) and A EXT
TRIG.
a. With low intensity level, set VERT MODE to X-V.
b. Adjust trigger LEVEL for TRIG'D LIGHT.
b. Adjust FOCUS and ASTIG (rear panel) for optimum
spot size.
c. At normal intensity check for intensity modulation.
c. Set INTENSITY and B INTENSITY CCW.
d. Change Type 191 to 2 V P-P and 2 MHz to EXT Z
AXIS blanking and A EXT TRIG. set TIME/DIV to 0.5ps.
d. Connect DVM to Z OUT DC test point (at rear of
Power Supply board) and note the DC voltage (normally in
the +7 to +11 V range).
e. Turn INTENSITY up and check for intensity modu
lation.
e. With the INTENSITY control, increase the DVM
13. CHECK AUTO FOCUS
reading by 4 V.
NOTE
f. Adjust GRID (R1660), located at rear of Horizontal
Amp board, so that the CRT spot is at the threshold of
visibility in low ambient light.
Adjustments and test points are located at the rear of
the Power Supply board.
a. Apply 2 div amplitude of 3 MHz to CH 1 input.
11. CHECK Z AXIS COMPENSATION and RISE
TIME
NOTE
b. Trigger CH 1, set TIME/DIV to 0.2/is/div, HORIZ
DISPLAY to A.
Adjustments and test points are located at the rear of
the Power Supply board.
c. With low intensity adjust the FOCUS and ASTIG
(rear panel) for the best defined 3 MHz trace.
5-10
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Tektronix 485 Specifications

General

Brand	Tektronix
Model	485
Category	Test Equipment
Language	English