Another Pioneer SX-737! Why won't the relay click in?

Need tools? Here's a video showing what I use (with links!): https://youtu.be/MLK649c1_fM In this video, I figure out why there is no sound out of this receiver. With these vintage stereos, sometimes the protection circuit may appear to be doing its job, but it might be faulty itself! This is what happened with this particular unit. In this video, I show how I found the issue and what I did to solve it.