Tektronix 485, Instruction Manual

Page: 61 / 197

Calibration—485/R485 Service
c. Adjust Input I (R206) fo r CH 1 and Input I (R306)
for CH 2, (located on front of Vertical board) fo r no trace
shift.
51. ADJUST V A R IA B L E BALANCE CH 1 and
CH 2
a. Set VOLTS/DIV to 10 mV; input to GND.
b. Rotate VARIABLE volts/div fully CCW. Adjust VAR
BAL (R215), (located on front of Vertical board) for less
than 0.1 div of shift while switching from Uncal to
calibrated.
c. Check for 0.2 div or less o f shift while rotating
VARIABLE CW to CCW.
d. Repeat in CH 2 adjusting NVB (R312) (located on
front of Vertical board).
e. Change CH 2 POLARITY to INVERT and repeat in
CH 2 adjusting INVB (R310) (located on front of Vertical
board).
52. ADJUST 5 m V /D IV BALANCE CH 1 and
CH 2
a. Set input to GND; POLARITY + UP; 10 mV/div.
b. Adjust R350, (located above U350) for no shift when
switching in CH 2 between 10 and 5 mV.
c. Recheck CH 2 variable balance.
d. Repeat in CH 1 adjusting R250 (located above
U250).
53. CHECK IN V E R T S H IF T
a. Set VARIABLE volts/div to cal; VOLTS/DIV to
5 mV; CH 2 to 50 f t ; VERT MODE to CH 2; then center
trace.
b. Switch CH 2 POLARITY between + UP and IN­
VERT.
c. Check for ±1.0 div of trace shift or less.
54. CHECK BEAM FIN D E R
a. Check that trace remains within the graticule area
with BEAM FINDER depressed.
b. Check beam finder operation under all combinations
of HORIZONTAL, CH 1, and CH 2 POSITION controls.
55. ADJUST LOW FREQ UENCY V E R T IC A L
T R A N S IE N T RESPONSE
a. These adjustment (part of MAIN VERT TRANS
RESP) are located at the rear of the Vertical board. They
are the first four pots above the MAIN VERT BAL
adjustment, and are adjusted beginning with the bottom
one first.
b. Input to 50 f t ; DC coupled. Connect the High
Amplitude Output of the Type 106 Square-Wave Generator
to CH 1 input.
c. Use a VOLTS/DIV setting of 0.5 V with the Type
106, and an on-screen amplitude of 5 to 6 divisions. Note
that the maximum output of this generator will trip the
50 f t RESET.
d. The adjustments are to be set for best flatness of the
top front corner of the square wave.
TABLE 5-6
TIM E/DIV SQUARE WAVE
Bottom Adjustment
(R606) 5 ms 100 Hz
Next Adjustment
(R607)
0.5 ms 1 kHz
Next Adjustment
(R608)
20 jus
20 kHz
Next Adjustment
(R609)
20
ms
20 kHz
c. Repeat step d as there may be interaction.
56. ADJUST CH 1 and CH 2 50 S I G A IN
a. Located next to second stage IC's towards front of
Vertical board.
b. Set VOLTS/DIV to 20 mV.
REV. B. AUG. 1975
5-17