How can I repair my dassh light problem?

When I turn on my parking lights or headlights. The dash lights go dim. Also the fuel gauge lights and Speedo lights go out. All the outside lights work just fine. I have installed all new light bulbs, New headlight switch, New flashers, New fuel tank switch. As far as I can see the printed circuit board looks healthy. Although I did have to put a piece of a business card under the circuit board for the instrument lights on the left side of dash. I also spread the copper "Tangs" so they would fit tighter. Didn't help!
Any help will be greatly appreciated.
Thank you in advance. JOSEKOOL39@HOTMAIL. COM