It happens on both channels the same. The wave amplitude is .54 Volts according to the scale.
I'll get a sinewave and try that.
Okay I hooked up my function generator and got a sinewave... At first, I didn't get the messed up triggering this time, it stayed clean down to the highest resolution. However, this time I got a very strange noise, completely messing up the waveform, that came in spells, almost as if from changing settings - and it went away after reducing the vertical resolution... Then it remained perfect when I increased it again.
Also, in certain timebase/vertical resolution combinations, I still got the double triggering, as if I was getting a trigger on both the rising and falling edge at the same trigger level.
Weird thing though, now that I have had the scope on for about ten minutes, the problems seem to have gone away. Almost as if it was a temperature thing. Is this normal?
EDIT: Okay the bidirectional trigger glitch thing started again on ONE SPECIFIC timebase / resolution combo, after I tried switching the triggering direction. It happens there on both channels: 5mV/div, .2ms/div. Note that it does NOT happen on .1ms/div or .5ms/div, nor on .2ms/div with 10mV/div, etc.
I could not reproduce the crazy noise glitch thing. I tried various things that might affect it while I had it, like touching the inputs, the coax cable and the bnc tees, etc... Now I'm wondering if it could have had anything to do with radiation from the CRT, if the cable was right in front of the trace.