Contents of an email from NH to OH and TD about tests performed on an additional bias supply:

This email was sent to you by someone outside the University.
You should only click on links or attachments if you are certain that the email is genuine and the content is safe.

so I looked at the other supply in the lab (in a NIM crate there, cable direct to DSO)

Still see the same noise wave - also it looked a lot worse at 50V but that may be a worse NIM crate or something else - the current also wasn't 0 (calibration?)

More unusually the signals remain even if the NIM crate is off (DSO_Lab_NoP) and when the SHV is removed from the HV completely (DSO_Lab_NoCable)