Specifications

Troubleshooting
59
TROUBLESHOOTING
To start, make sure that the power entry module on
the rear panel is set for the ac line voltage in your
area and that the correct fuse is installed. The
selected ac voltage may be seen through the
window on the power entry module. Verify that
the line cord is plugged all the way into the power
entry module and that the power button on the
front panel is pressed in.
LCD CONTRAST
If there are no characters on the LCD, or the
contrast is very poor, go to the LCD CONTRAST
line of the SETUP menu and use the spin knob to
adjust the contrast. Larger values increase the
contrast.
FAN
The fan in the SR400 is temperature controlled.
When the unit is cold, the fan is off. When the
internal temperature reaches about 30° C, the fan
starts to blow. Do not block the vents in the
chassis or the unit may not operate properly.
FRONT PANEL TEST
The keyboard, knob, display, and LED indicators
may be tested in the front panel test mode. Turn
the unit on while holding down the COM key to
enter the front panel test. The LCD should display
the message FRONT PANEL TEST. Pressing a
key will cause the LCD to display the name of the
key on both lines of the display. If the keys do not
work properly, check to make sure that there are
no keys stuck in the down position. Turning the
knob will light each LED one at a time in
succession across the front panel.
POWER ON RESET
If the instrument turns on with odd combinations
of LED's on, a garbled message on the LCD, or is
unresponsive to the keyboard or knob, then the
memory contents may have been corrupted
causing the instrument to "hang". To remedy the
situation, turn the unit off and hold down the
STOP key while turning the unit back on. This
causes the unit to reinitialize the memory and
assume the default setup.
QUICK TEST
Unplug all cables from the unit and recall the
default setup by holding the STOP key down
while turning the unit on. The message RECALL
DEFAULT should appear on the display for ~3 s.
Press the DOWN key once to go to the A=INPUT
1 menu line. Rotate the knob until A=10 MHz
appears on the menu line. To start a count period,
press the START key once. The data display
should show counting in counter A for 1 second
and stop at A= 10000000. Counter A will have
counted the internal 10 MHz timebase for 1
second and reached 10,000,000 counts. To reset
the counter, press the STOP key. The data display
should reset to 0.
Now press the DOWN key 3 more times to display
the N PERIODS line. Rotate the knob until N
PERIODS=10. Start a scan by pressing the
START key. The counter should cycle through 10
count periods separated by the default dwell time
(1 s). The display shows the current scan position
in brackets. Reset the scan using the STOP key.
Start another scan with the START key but press
the STOP key before all 10 count periods are
completed. This pauses the scan at the last
completed count period. START will resume the
scan and STOP will reset the scan.
In general, if the START key doesn't start a
count period it is because the counters are
paused at the end of a scan. In this case, the
SCAN led will be off and the N PERIODS
display shows that the programmed number of
points has been taken. A STOP is required to
reset the scan.
Pressing the STOP key twice in succession
always resets the counters.