Jeff:

Sounds like you didn't mess anything up. Was this the factory radio or had someone else done an aftermarket installation? You should have two hot wires for the radio -- one from the ignition switch and one from the headlight switch. Wires will be red or black red. One ground, usually chassis (will be a brown wire if separate). Speaker wires are colored, you should have four speakers, but there is a balance control on the console, so the wires may to there in two sets, not four.

At any rate, you need to scare up a wiring diagram and start tracing wires. Somewhere there is either a short or an inapropriate ground fouling things up.

It is also possible that the ignition switch is bad, not turning on the power for some accessories, or that one of the buss wires under the battery cable at the starter is off, so you have no juice.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!