Tektronix 485, Instruction Manual

Page: 52 / 197

Calibration—4 8 5 /R 4 8 5 Service
HORIZ DISPLAY to INTEN; B TRIGGER SOURCE to B
RUNS AFTER DELAY TIME.
b. Trigger A on + SLOPE. Use DELAY TIME POSITION
control to position the intensified portion of the negative
step near center screen.
c. Switch HORIZ DISPLAY to B and position the
negative step to center screen.
d. Switch A SLOPE polarity and check that the
transition changes less than 3 divisions horizontally.
24. CHECK D E L A Y JITTE R
a. Set A TIM E/DIV to 1 ms; B trigger source to B RUNS
AFTER DELAY TIME. Set B TIM E/D IV to 1 ps and
Time-Mark generator to 1 ms. Set HORIZ DISPLAY to
A L T ; use A trigger LEVEL to obtain a stable display.
b. Set HORIZ DISPLAY to B. Rotate DELAY TIME
POSITION dial from 1 to 9, checking for 0.5 div of jitter or
less on B display.
SCALE ILLUM CCW
BW LIM IT
CH 1 and CH 2
OFF
VOLTS/DIV 0.1 V
VARIABLE CAL
INPUT GND
POSITION
MIDR
1 M ft/50 f t 50 f t
VERT MODE
CH 1
IN TTR IG NORM
CH 2 POLARITY
+ UP
SWEEP MODE
A and B TRIGGER NORM TRIG
COUPLING
AC
LEVEL
MIDR
SLOPE
+
A TRIGGER SOURCE
INT
B TRIGGER SOURCE B RUNS AFTER DELAY
TIME
POSITION (HORIZ) MIDR
HORIZ DISPLAY A
TRACE SEPARATION MIDR
CAL 5 V FREQ 1 MHz
TIM E/D IV
1 ms
DELAY TIME POSITION 4.00
25. CHECK IN PU T PRO TECTIO N TR IP LEVELS
for CH 1 and CH 2
a. Set Type 106 High Amplitude control to minimum;
Frequency to 1 kHz and Symmetry for 50% duty cycle. Set
CH 1 and CH 2 inputs to DC; VOLTS/DIV to 2 V; position
trace to top graticule line; input impedance to 50 ft.
b. Connect Type 106 High Amplitude to CH 1 input;
slowly increase Type 106 amplitude.
c. Check that the input disconnects (trace returns to top
graticule line) and reset lamp lights after the trace crosses
the 2.8 graticule division point and before it reaches the
4.25 division point. Return Type 106 amplitude to m ini­
mum and repeat for CH 2.
1. CHECK +59.4 V SUPPLY (±0.06 V )
a. Using DVM measure at +59.4 V test point on Power
Supply board.
b. If necessary adjust +59.4 (R1940).
c. INTERACTION will affect the operation of most
circuits in the 485.
2. CHECK +50 V SUPPLY (±0.05 V )
a. Measure at +50 V test point on Power Supply board.
PART 2 - 485 C A L IB R A T IO N PROCEDURE
Remove the wrap-around cover as described in the
Maintenance Section.
Connect the 485 to a pow er source which meets specified
voltage and frequency requirements. Press the POWER
pushbutton to turn the 485 on and allow i t to warmup fo r
a t least 20 minutes before commencing Part 2 Calibration
procedure. This instrum ent should be adjusted a t an
ambient temperature o f +25°C f±5°C) fo r best overall
accuracy.
Preliminary Control Settings
CONTROL
INTENSITY CCW
B INTENSITY CCW
b. If necessary adjust +50 V (R2048).
c. INTERACTION will affect the operation of most
circuits in the 485.
3. CHECK LOW
Ground Reference
Board)
5 V +0.1 V
+15 V +0.25 V
- 5 V ±0.1 V
- 1 5 V ±0.3 V
-5 .5 V ±0.25 V
+5.5 V ±0.25 V
Point on Power Supply
—9 V ±0.15 V
+9 V ±0.15 V
+25 V ±0.6 V
+120 V ±2.4 V
+180 V ±3.6 V
V O L T A G E SUPPLIES (Use
Test
5-8
REV. C, SEPT. 1974