Tektronix 7B70 Time Base Instruction Manual page 41

Insert the 7870 and a calibrated vertical
unit into a calibrated oscilloscope. Turn
the power on and allow 5 minutes warm-
up. Check that all pushbuttons light
when pressed.
U l
Lrase.
I
Check horizontal preamp.
I
buttons light
4 z
7 1
0
it
race more than
buttons do
Set t h e horizontal and vertical POSI-
T I O N controls t o midrange. Press the
top TRIGGERING buttons. set TIME1
D I V t o .5 ms, MAGNIFIER t o X I and
vertical VOLTSIDIV t o 10 mV. Advance
the Intensity until a free running trace is
observed.
I
- -
Set the oscilloscope calibrator t o I kHz
five cycles
_
Check VARIABLE TIME1
and 40 mV. Connect the calibrator out-
unstable or
-
D I V control.
put t o the vertical unit. Check for about
no display
5 cycles/l0 divisions.
Check calibrator output
with test oscillosco~e.
not light
'--
yes
Check at
+5
volt test point
f o r +5 V. Check push-
button light bulbs.
V)
MAGNIFIER X I 0 button. Check for
-
Replace vertical unit
no output
Refer to oscilloscope manual.
a
P
Set the 7870 COUPLING
lit
_
t o EXT and apply a 1 kHz
Check trigger amplifier and
light. signal t o the EXT TRIG I N
trigger generator circuits.
connector.
TRIG'D lamp
is lit
1
Check horizontal preamp.
Check SOURCE switch
and associated relavs.
-
trace appears
C
1
E.
I
Place the 7870 in the oscilloscope B hor-
I
- . . ..
I
z
no sweep
I
Set the oscilloscope horizontai mode t o
ALT. Check for two traces on the CRT.
I
no trace
:
I
izontal compartment and another time
base in the A horizontal com~artment.
I
-..-
_..-_..
for movement of trace.
I
0
trace appears
0
a l
no trace
= Remove vertical unit from
oscilloscope. Check for
trace.
I
trace moves
only one trace
of Q410 for proper input
from oscilloscope.
Check 7 8 7 0 c o n t r o l settings
( M O D E must be P-P AUTO or
AUTO). Check sweep output.
Time base in the A hori-
zontal compartment is not
functioning.
R o t a t e t h e 7 B 7 0 POSI-
T l n N cnntrnl and F~L,-k
Fig. 4-2. Troubleshooting chart for the 7670.
output Check sweep generator and W
Check sweep inhibit cir-
trace does not move
;
1
cuit. check at the emitter
I
trigger generator circuits.
h l
8
0