EDU09 - PC screen showing readings when not connected

When the scope is running the screen shows readings when nothing is connected to the EDU09 probes - is this some interference from the laptop?

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Image1 15.12.2022 NRG EDU09

Thanks for your patience.

This is OK.
There is only one bit “jumps” in the trace, due to rounding.
This is normal due to the vertical resolution of 255 levels.

Do you get readings if you connect the probe to a signal source?

The main problem seems to be too big offset due to too high voltage on pin 1 of IC2.

IC2 not running is reading 1.71,
IC2 running is now reading 1.71 - I do not know why this has changed from the previous 2.38, I haven’t done anything to the board.

When connected to a EDU06 board as Experiment 1 the reading on the screen is attached and IC2 pin 1 reads 0.04! Disconnecting the positive lead from EDU06 board the reading returns to 1.71.

Image 2 15.12.22 at 19.12 NRG EDU09