@orthomead,
(I am reposting since I accidently addressed this to wrong person. I deleted my prior post.)
To follow on what @mijostyn said, MIL-HDBK-263B does state - "Some metals, can create significant charges from triboelectric generation. Aluminum, when rubbed with a common plastic can generate substantial electrostatic charges." This then potentially may provide some insight into what you have experienced as follows:
The Archromat from what I read appears to be essentially porous acrylic mat with solid top/bottom faces/sheet. But acrylic has a fairly large triboelectric difference with PVC so one could the predict the opposite of what you experienced which then adds to the observation that @mijostyn made that the mat is insulating the record from the platter.
When you grounded the platter bearing - did you measure the resistance (simple multimeter will work) from the platter surface to the wall ground point? When I grounded my VPI 2" aluminum platter/bearing I had some issues getting it to work for me. The wire type and length can have an effect - my wire length was 8ft. Realistically, providing the lowest impedance path to ground is the goal and that is all about surface area not gauge. Tinned-copper braided cable at 1/4-inch wide is readily available and can be used to easily assemble a low impedance ground cable using appropriate end-connectors, 1/4-inch PET expandable braided sleeving for appearance and protection, and heat shrink to seal the ends. A 1/-4-inch wide tinned-copper braided cable measured about 0.4-ohms while a single gauge (18-ga) wire ground measure about 1.2-ohms. I was able to get the platter to outlet resistance to about 1.5-ohms; and I had to ground it to the source of power to the turntable motor for best results.
Just some thoughts,
Neil
(I am reposting since I accidently addressed this to wrong person. I deleted my prior post.)
To follow on what @mijostyn said, MIL-HDBK-263B does state - "Some metals, can create significant charges from triboelectric generation. Aluminum, when rubbed with a common plastic can generate substantial electrostatic charges." This then potentially may provide some insight into what you have experienced as follows:
The Archromat from what I read appears to be essentially porous acrylic mat with solid top/bottom faces/sheet. But acrylic has a fairly large triboelectric difference with PVC so one could the predict the opposite of what you experienced which then adds to the observation that @mijostyn made that the mat is insulating the record from the platter.
When you grounded the platter bearing - did you measure the resistance (simple multimeter will work) from the platter surface to the wall ground point? When I grounded my VPI 2" aluminum platter/bearing I had some issues getting it to work for me. The wire type and length can have an effect - my wire length was 8ft. Realistically, providing the lowest impedance path to ground is the goal and that is all about surface area not gauge. Tinned-copper braided cable at 1/4-inch wide is readily available and can be used to easily assemble a low impedance ground cable using appropriate end-connectors, 1/4-inch PET expandable braided sleeving for appearance and protection, and heat shrink to seal the ends. A 1/-4-inch wide tinned-copper braided cable measured about 0.4-ohms while a single gauge (18-ga) wire ground measure about 1.2-ohms. I was able to get the platter to outlet resistance to about 1.5-ohms; and I had to ground it to the source of power to the turntable motor for best results.
Just some thoughts,
Neil