I applied the patch to my scope, too.
Today I noticed that my channel 1 and 2 are a bit off.
This means when nothing is connected to the probes one shows a lower voltage then the other channel.
Attached a picture of all four channels without a probe connected, averaged and maximum memory depth set to 1k - to see it clearly.
It is visible that the channels are not exactly zeroed.
Does that mean my scope is damaged?
Or is it working and a difference of up to 300µV is totally fine?
Best,
Philipp
EDIT:
I did a self-calibration of the scope before I took the picture.
It was up and running for around 2 hours before, so should be warmed up enough.
EDIT 2:
The difference scales with the voltage per division setting.
With 2V per division it is around 3mV off.
What you read from the instrument with no probes connected is pretty meaningless. What would you expect to read with nothing connected? (I'd expect to read the Johnson-Nyquist noise of the the 1M terminating impedance. 1M@20ºC, 300MHz => 2.2mV rms, ~13mV ptp).
Remember that this is an 8 bit instrument with a 3% DC gain accuracy specification. So if you've got it set to 2V/div that's a 16V range which gives you an LSB of 16V/2^8 = 16V/256 = 62.5 mV. So that 3mV offset is less than one LSB (the minimum step difference that the instrument can measure) by a factor of twenty -
it is well beyond what the instrument is actually capable of resolving even before you take the specified accuracy into consideration. It is nothing more or less than an artefact of the scope trying to calibrate itself by using lots of averaging, in practical measurement terms it means nothing.
Your expectation that 3mV
might mean something at 2V/div is a very strong indicator that you don't understand the basics of the instrument or its limitations. I'd suggest a bit more basic study is required or you're in danger of misunderstanding what the scope is really telling you about what you're measuring with it. Don't expect an 8 bit scope (or for that matter, any scope) to deliver much in the way of accuracy or precision.