Tektronix 570, Manual

Page: 40 / 134

C arefully force the mounting post into the
nylon collars.
Snip off the portion of the
mounting post which protrudes below the nylon
collar on the reverse side of the chassis.
NOTE
Considerable force may be neces­
sary to push the mounting rods into
the nylon collars. Be sure that you
apply this force to that area of the
ceramic strip directly above the
mounting rods.
TROUBLESHOOTING
This section of the manual contains infor­
m ation for troubleshooting your oscilloscope.
B efore attempting to troubleshoot the instru­
ment , however , make sure that any apparent
trouble is actually due to a malfunction within
the instrument and not to improper control
s ettings. Instructions for the operation of the
o scilloscope are contained in the Operating
Instructions section of this manual.
If your Type 570 Osci lloscope fails to operat e ,
m ake s u r e that i t i s properly connected to a
source of power.
If
the pilot lamp on the
front pane l, and the fan at the rear of the
instrument , do not come on when the instrument
is turned on , check the source of power , the
power cord connections and the power line fuse.
If the instrument is turned on, but no spot
or trace is visible on the crt, check the
POSITION and INTENSITY controls. Be sure
that the signal is not driving the beam off the
s c reen.
Troubles are usually caused by tube failure ,
and you can frequently correct them by finding
the bad tube and replacing it with a good one.
However sometimes a tube burns up resistors
or overstresses capacitors when it fails. In
these cases you will also have to find the bad
components . Sometimes you can find them by
visual inspection. One way to find bad tubes
i s to try replacing suspected tubes with good
ones. If possible , replace all suspected tubes
at one time. and if the trouble is eliminated,
return the old tubes , one at a time. until the
offending one is discovered.
Although your Type 570 Oscilloscope is a
complex instrument . it can be conveniently
divided into basic circuits, as shown on the
B lock Diagram. The first circuits
to
check,
for practically any type of troubl e , are the low­
voltage power supplies.
Proper operation
of every circuit in the Type 570 Oscilloscope
depends on proper operation of the regulated and
u nregulated power supplies.
All the regulated supplies should be within
five per cent of their rated values and should
remain steady as the line voltage is varied
from 105 to 1 25 volts or 210 to 250 volts .
S e e the Calibration Procedure for the low­
voltage power supply test points.
WARNING
B e careful of the power-su pply volt­
ages. The lower-voltage buses are
considerably more dangerous than
the high voltages in the crt circuit,
due to the higher current capabili­
ties and the larger filter capacitors
u s ed.
All low-voltage power supply capac ­
itors should be discharged prior to
working on the instrument. This
p rocedure must be used when work­
ing around or on the Floating Power
S u pply.
The cathode- r ay tube display can help in
locating the source of trouble. If there is
a horizontal trace on the crt but no vertical
deflection , check the P late Sweep Generator and
V e rtical Amplifier fuses in the top access panel
o r on the front panel, depending upon serial
r ange of instrument.
If
no spot is visible check the positioning
controls. Then advance the INTENSITY Control
to see if there is a glow indicating a spot
positioned off the crt. If no spot can be
obtained short the horizontal deflection plates
together and the vertical plates together.
If
no spot is obtained check the high voltage
power supply and the crt.
If the spot is returned to the screen by
s horting the deflection plates , check the de­
flection amplifier concerned.
If an abnormal display is obtained on the crt ,
the Block Diagram along with the knowledge
of how the instrument works , will enable the
trouble producing circuit to be determined. The
4 - 4 M aintenance - Type 570
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