Most detail response from any thread so far is this;
"The newer AC30's I've seen with pc boards and a "star" ground near the PT have several problems regarding hum/buzz. There is a an issue of bad grounding on the PC board as well as the lack of shielding to the input grids of the Norm & Brilliant channels. To fix it requires cutting some traces and running jumpers to the star ground as well as changing the location of the input resistors, grounding the resulting unused traces and adding shielded wire to the 1st stage preamp tube grids. I recently had a new HW series AC30 with a noise problem. All it required was a couple of tie-wrap blocks and bundle ties to hold one wire in place on the chassis."
I read somewhere that VOX sent out modifications when asked, so I am hoping that there is a schematic from them....
If not, I will go through this process.