28
Subject to change without notice
3-3.1
FOCUS setting without effect.
Check the voltage at the FOCUS potentiometer sliding contact
(wiper) can be changed between 0 and +12 Volt. This contact
is directly accessible on the soldering side of the FC board.
If the voltage can be changed between 0 and +12 V, continue
with item 3-3.3.
If the voltage can not be changed between 0 and +12 V, con-
tinue with item 3-3.2
3-3.2
Replace the FC board as described in section Board Re-
placement.
3-3.3
Switch the oscilloscope off, press connector P4004 on TB
board and pull the 4 wire ribbon cable (out). Switch the
oscilloscope on again.
Measure the dc voltage at pin 4 with respect to chassis and
turn the FOCUS between left and right stop.
If the voltage can be changed between approx. -2 V and +2 V,
continue with item 3-3.4.
If the voltage can not be changed between approx. -2 V and
+2 V, continue with item 3-3.5.
3-3.4
Replace the CR board as described in section Board Re-
placement.
3-3.5
Replace the TB board as described in section Board Re-
placement.
Item
Behavior of the Instrument
Possible Reason / What to do
Remark
3-4.1
No X defl ection or distorted X
defl ection in all modes.
Replace the XY board as described in section Board Re-
placement.
Item
Behavior of the Instrument
Possible Reason / What to do
Remark
3-5.1
No trace in time base (Yt) mode.
Component-Tester and XY mode
OK.
Check that all pushbuttons except the POWER pushbutton
are released (out).
Normal triggering without
trigger signal would have
the same effect.
3-5.2
Switch the oscilloscope off.
Locate the long ribbon cable connecting the FC with the YP
board. Note the instructions of item 4 (FC Board) in the sec-
tion Board Replacement and remove the plug at connector
J2006.
Locate the short ribbon cable connecting the FC board with
the TB board. Note the instructions of item 5 (FC Board)
in the section Board Replacement and remove the plug at
connector P4002.
Connect the ribbon cables of a spare FC board and con-
nect them with J2006 and P4002. Set all potentiometers to
midrange position and release all pushbuttons (out).
Switch the oscilloscope on.
– If trace is visible now, continue with item 3-5.3.
– Otherwise continue with item 3-5.4.
The FC board replacement
enables a fast check of the
instrument control.
As the trace rotation coil
is still soldered on the
original FC board during
this procedure, the trace
will be tilted if visible.
3-5.3
Replace the FC board as described in section Board Re-
placement.
Item
Behavior of the Instrument
Possible Reason / What to do
Remark
H M 3 0 3 - 6 T r o u b l e s h o o t i n g
