Hi hogoat70,
Welcome to the Heartland Owners Forum.
The red LED next to each fuse illuminates if the fuse is open (or removed) AND there's a load on the circuit, which provides a path to ground.
So if it illuminates when you pull the fuse, that means there's a load. If it's not illuminated with the fuse in place, then the fuse was ok, and the new one is ok.
If this is the circuit for the TV antenna signal booster, the red light on the signal booster should go on and off as you push the button in and then push again to release it. Also, if you have TV stations within range, with the signal booster ON, you should get reception.
If the TV is working, then the signal booster is getting power.
Whether the stereo is on the same fuse is something I don't know. But if it is, and the TV works, then there's a problem with the stereo either getting power, or maybe it's just broken.