Tektronix T922 User Manual

a . Does beam appear on screen? If not, rotate INTEN-
SITY control clockwise while holding BEAM FINDER
button in
until
beam appears or control is
fully
clockwise .
If beam does not appear, the trouble may be in the power
supplies (see Power Supply schematic) .
b . Check all low voltage power supplies, starting with
-8 V (-8 V is reference supply), the +8 V, and +100 V at
appropriate test points .
(1) If no voltage is present, check F700 .
(2) If -8V is low (or zero), check Q772,0774,
0776, or
U742 .
(3) If -8 V is correct but +8 V is low (or zero), check
0752, Q754, Q756, and U742 (U742 is used
for
both
-8
and +8 V supplies) .
c . Check high-voltage supplies (see CRT and Vertical
Amplifier schematic)
.
(1) Check for -2 kV
at pin
1,
P465, or pin 2, crt base
socket . Use DVM for all voltage checks in this circuit
to
prevent circuit loading .
(2) If no -2 kV, check for 50 kHz sine wave (ap-
proximately 200 V, peak-to-peak)
at
pin
5 of T460
(high-voltage transformer primary) .
(3) If neither -2kV or 50 kHz sine wave is present,
check Q454,Q458, and Q446 .
Do not unload the secondary of the high-voltage
transformer, T460 ; the transformer may be damag-
ed .
Z Axis . SYMPTOM-No intensity or no control over
intensity (BEAM FINDER button pushed) .
a . Does beam come on screen? If not, and low and high-
voltage supplies are correct, trouble may be in Z-Axis
circuit (see CRT and Vertical Amplifier
schematic) .
(1) Check for approximately 60 V swing between crt-
socket pins 2 and 3 . If no voltage swing, trouble may be
in unblanking .
(2) Check for positive-going pulse at Q416 emitter . This
pulse amplitude should
vary from 20
to
80 mV with
change
(fully
cw to
fully ccw) in INTENSITY control
position
.
REV . D JUL 1977
Service Information-T921/T922/T922R
(3) Check for 0-40 V, peak-to-peak unblanking pulse
(varies with INTENSITY control
position) at Q426
collector .
(4) If no unblanking pulse, check Q426,Q424,Q416, or
0434 .
Vertical : SYMPTOM 1 .-No trace on crt with BEAM
FINDER button pushed, or vertical POSITION control
does not center display (see Vert Input, Vert switching,
and Crt & Vert Ampl schematics) .
a . If trace is on screen, but about 2 cm above graticule
center, it indicates trouble in vertical amplifier .
b .
Short P4-9 to P4-11 (A8, Vertical board) . If trace
does not center, trouble is in output circuits .
Check Q112,
0122, Q134,0144,Q136, and
Q146 .
c .
If
trace
centers with pins 9 and 11 short-circuited,
trouble is ahead of P4 .
d . Short-circuit 04322 collector to 04324
collector . If
trace centers, trouble is ahead of delay-line drivers,
04336-04346 .
e . Check voltage at 04302 and 04303 emitters . Each
should read approximately +5 V above ground . If emitter
voltage is okay, trouble is either in 04302 or 04303, or in
switching circuit (short-circuited CR4314,CR4303, or
openCR4304) .
SYMPTOM 2 .-With 50 mV input and VOLTS/DIVset to
10 mV, crt display is low and does not position above
graticule center .
a . Press BEAM FINDER button . If trace does not appear
on screen, rotate vertical POSITION control .
b . If trace appears, but decreases
in amplitude at
graticule center, suspect vertical output circuit .
c . Short-circuit Q136 collector to Q146 collector . If
trace centers, short-circuit Q112 collector to Q122 collec-
tor . Trace should center .
If
not, suspect
Q112,Q134, or
0136 .
Triggering : SYMPTOM 1 .-Trace free runs, does not
trigger in AUTO or NORM (see Trigger schematic) .
a . Set TRIGGERING MODE to AUTO . Turn LEVEL
control cw and ccw to both limits . Does the trace flicker? If
not, triggering signal is not reaching sweep circuit .
5-9

Tektronix T922 Specifications

General

Brand	Tektronix
Model	T922
Category	Test Equipment
Language	English