1991 isuzu npr power problem

[davesmcd]

I have a 1991 Isuzu NPR, I was going to check my lights to see what bulbs needed replaced. I simply turned the ignition key to the on position, my dashboard lit up as usual, I turned the knob for my headlights to the ON position and everything went black. The dashboard went out and now I have no power to anything. I checked all the fuses, checked the battery, ground.

Is there an in-line fuse somewhere that I am not finding? What could possibly be causing me to have no power?