20
MAINTENANCE
W A R N I N G
The following instructions are for use by
qualified service personnel only. To
avoid electrical shock, do not perform
any servicing other than contained in
the operating instructions unless you
are qualified to do so.
High voltage up to 2000 V is present
when covers are removed and the unit is
operating. Remember that high voltage
may be retained indefinitely on high
voltage capacitors. Also remember that
ac line voltage is present on line voltage
input circuits any time the instrument is
plugged into an ac outlet, even if turned
of. Unplug the oscilloscope and dis-
charge high voltage capacitors before
performing service procedures.
FUSE REPLACEMENT
If the fuse blows, the “ON” indicator will not light and
the oscilloscope will not operate. The fuse should not
normally open unless a problem has developed in the unit.
Try to determine and correct the cause of the blown fuse,
then replace only with the correct value fuse. For 110/125
V line voltage operation, use an 800 mA, 250 V fuse. For
220/240 V line voltage operation, use a 600 mA, 250 V
fuse. The fuse is located on the rear panel adjacent to the
power cord receptacle.
Remove the fuseholder assembly as follows:
1.
Unplug the power cord from rear of scope.
2.
Insert a small screwdriver in fuseholder slot
(located between fuseholder and receptacle). Pry
fuseholder away from receptacle.
3.
When reinstalling fuseholder, be sure that the fuse
is installed so that the correct line voltage is selected
(see LINE VOLTAGE SELECTION).
LINE VOLTAGE SELECTION
To select the desired line voltage, simply insert the fuse
and fuse holder so that the appropriate voltage is pointed to
by the arrow. Be sure to use the proper value fuse (see
label on rear panel).
PERIODIC ADJUSTMENTS
Probe compensation and trace rotation adjustments should be
checked periodically and adjusted if required. These procedures are
given below.
P r o b e C o m p e n s a t i o n
1.
Connect probes to
CH 1
and
CH 2
input jacks. Per-form
procedure for each probe, one probe at a time.
2.
Set the probe to X10 (compensation adjustment is not possible
in the X1 position).
3.
Touch tip of probe to
CAL
terminal.
4.
Adjust oscilloscope controls to display 3 or 4 cycles of
CAL
square wave at 5 or 6 divisions amplitude.
5.
Adjust compensation trimmer on probe for optimum square
wave (minimum overshoot, rounding off, and tilt). Refer to Fig.
5.
Fig. 5. Probe Compensation Adjustment.
T r a c e R o t a t i o n A d j u s t m e n t
1.
Set oscilloscope controls for a single trace display in
CH 1
mode, and with the channel 1
AC-GND-DC
switch set to
GND.
2.
Use the channel 1 POSition control to position the trace over
the center horizontal line on the graticule scale. The trace
should be exactly parallel with the horizontal line.
3.
Use the
TRACE ROTATION
adjustment on the front panel
to eliminate any trace tilt.
Correct
Compensation
Over
Compensation
Insufficient
Compensation
