Has anyone else turned on their SDS800X to find a fixed DC offset (~700 mV) on CH1 and CH1 only? This has happened twice to mine immediately at power-on on two different days. CH2, CH3, and CH4 all had no offset (i.e. 0) as expected. Nothing was connected to any of the inputs. Selecting the vertical position rotor and pushing to return CH1 trace to 0 had no effect and in the CH1 “box” (bottom left of screen) showed, IIRC, 0 mV. Scrolling the position down to place the trace on 0 would then show a negative offset. Setting the vertical position explicitly in the CH1 position entry box to 0 would position the trace to 0+~700mV.
Shutdown, disconnect power, reboot, and set to default had no effect (something bad stored?). In each case to get the scope back to powering on with DC offset of 0, I set the scope to default and then ran selfcal after warming up for 30 minutes. Once the selfcal completed the offset was now at 0. I rebooted the scope and the offset was still gone. Rebooting a few more times and the offset did not reappear. So I continued my actual testing for the day.
After a couple of days not being used, I turned on the scope yesterday and the offset returned for a second time. Same investigation and results as the above paragraph. I then again continued my actual testing for the day.
I turned the SDS800X on today and the offset remains at 0.
I will say that “testing for the day” was looking at a 5V/12V rail-splitter with DC coupling and using the vertical position offsets at -2.5V and -6.0V to see what ripple, noise, and droop were present under differing loads, 10X attenuation and 10mV/, and running FFTs. Maybe this is related. But then it didn’t reappear this morning.
Anyone else seen this?