AFAIK there is just one 14.318MHz crystal (not an oscillator) on the 5150 motherboard, right next to the 8284. It’s a flat metal component with two leads coming out of it from one side, probably marked with 14.318MHz. There might be a solid wire soldered to its housing, going across it. I’m notpretty sure how it was markedlabeled as Y1 on the PCB.