Insulator/shielding in DEC power supply

Ian> I'm reconditioning some H7100A power supply units in a Ian> VAX-11/785, and I've come across something I haven't seen Ian> before. I'm hoping one of you has. :) This particular PSU was Ian> labeled 'Memory Power Supply' and has additional regulator Ian> boards for a 15v rail. Slipped between those boards were two Ian> sheets of what looked like heavy-duty paper. However, one had Ian> delaminated, demonstrating that it is a sheet of thin copper Ian> sandwiched between two paper-like layers. That suggests to me Ian> that this was intended more for EMI shielding than electrical Ian> isolation. I did not see these sheets in another PSU that also Ian> had a supplemental regulator. It may be a design change made to handle the FCC emissions regulations. I'd say both paper and copper are important; the copper for EMI, the paper to avoid shorting out the boards. paul