'77 Vandura radio not working

[89Suburban]

Another pic

Nice mags

 

[Turbo4whl]

so wired directly to the battery sounds like they werent using the Radio tap on the fuse panel. @Turbo4whl were you an expert on the fuse panels? Someone here is very knowledgeable. Im thinking the switched ignition is the tap, and the fuse itself is the constant.

Taylor, since you asked, the old GM fuse panel had some hidden features. You can easily see in @heartbraker666 picture the 3 vertical fuses at the bottom are key on switched. Hidden feature #1: The radio will not work if the backup lights have a short and burn the fuse. This is a safety feature to let you know you have no backup lights.

Moving to the headlight switch, it has several power feeds, all are hot all the time. Easy to see in the fuse panel the taillight and parking light fuse. The brake light fuse also feeds the headlight switch for the dash lights. Current through the panel resister, back to the fuse panel at the 3 amp fuse, then to the gauge cluster light and radio light. (factory radio) This is hidden feature #2: Panel lights out, maybe no brake lights. The next power feed to the headlight switch for the headlights, no fuse. The headlights have a circuit breaker. Where is this... in the headlight switch! This feature #3, allows the headlights to re-light if the short is intermittent.

Don't want to forget the last headlight switch power feed. It is from the dome lights, hot all the time, so the switch completes the ground. Yeah, headlight switch has a ground wire, or the mounting bracket will ground it.

For Allie back to the radio. Factory radio has a 6 or 8 connection gang plug. Some people don't use it for a aftermarket radio. Some others will cut it off and butt connect wires. You can, or could use a jumper plug that matches the GM plug too.