I vacuumed inside the HV cage, though it has many small areas that are difficult to access so I am not sure how great a job I did.

Turned the bias up and again at 55kV I hear small sparks near the end of the HV duct that brings the cables from the rack. Cannot see anything. If it is really sparking where it sounds like sparking, it must be from the edge of the duct to the faraday cage.

Changing the EZL voltage and the EE voltage has no effect on where it starts sparking.