What steps do I need to take to figure out why my record player isn't

Hi,

Your model is an “idler” type turntable which means that the platter is driven by a rubber wheel attached to the motor which turns the platter. No belts involved.

You need to prove the circuit from the power cord plug through to the motor via the switches and progress from there.

You will need to have a DMM (digital multimeter) and know how to use its’ Ohmmeter function to test for continuity from the power cord through to the motor.

This is the safe way to test as no potentially lethal power is involved as the power should be disconnected from the turntable when using an Ohmmeter

There is a service manual available which should help but you have to register to access it. (The PS1150 is a close enough model to help with working on the PS1100)