How to fix the speakers in my 1990 ford f150 lariat?

The speakers in my 1990 ford f150 lariat suddenly stopped working. The radio powers on fine just no sound coming from the speakers, I couldn't seem to locate sny fuse or relay specifically for the speakers, hoe do I fix this?

Check the wires from the radio to speakers.

If all the speakers stopped working at the same time, then then chances are the wire leads from the radio's wiring harness to the front and/or rear speakers is cut or has otherwise failed. If it's not that, then the head unit itself may be on the way out.

The built-in amp in the radio head probably went bad. It's understandable being a 25 year old setup.

There are no fuses between the head & the speakers. As all of them quit at the same time, suspect the head unit.