[Mondial]

Tim, did you try removing the connection on the rectifier terminal strip between the bridge rectifier negative and the adjacent chassis ground lug? 

My suggestion would be to have the bridge negative be isolated from chassis at that point and connect bridge negative directly to the big filter caps negative. Then connect the big cap negative with another separate wire to chassis and circuit ground. Wired this way, all the ripple current flows directly to the filter caps without any alternate path through the chassis or PCB grounds.