Thank you, Mark.

Yes,scope can not see trigger signals.

I connected ch1 probe to probe calibrator out put whitch built in.
Probe and trigger mode is set to DC coupling mode.
Trigger source is set to ch1.
I set trigger level to half level of Probe calibrator output.
The trigger level is maybe set properly.

In this condition,
Most time LeCroy 9450A Oscilloscope works looks like perfectly.
But occasionaly LeCroy 9450A Oscilloscope lost trigger signals.
LeCroy 9450A Oscilloscope displayed "NO or SLOW TRIGGER".
I do not change any settings.

Then I set to trigger mode to auto.
LeCroy 9450A Oscilloscope display Probe calibrator signal
in free running mode not triggered.
I change trigger level or other condition.
Displayed signal is not changed---free run signal is seen.

I think
LeCroy 9450A Oscilloscope has intermittent trouble in triggered mode.
I want to fix this trouble.

Please Advice me another point.

Thank you Kishikawa.

"Mark" wrote in message
oups.com...
that means the scope is not seeing a trigger signal.

the scope may be broken or you may not have it set up right

did you select the trigger source to the channel you are looking at?

Mark