How to know what's getting power

I recently bought my second system with a turntable, vintage receiver and eq. Everything was working when I listened at the lady's house but after I got the system home, if I use the eq, the sound only comes out one side. If I reverse the cables, sound comes out the other side. If I turn off the eq and just use the receiver, sound comes out both sides as normal. I took a picture of how everything was wired and made sure I've got it set up the same way. I also upraded the av cables to no avail.

So, I'm thinking that one set of "sockets" aren't working on either the eq or the receiver. Is there a way to see which is which without buying other components?

 

Hi Steeler, welcome to the Forum.
Firstly, how have you connected the equaliser? Posting a photo would be useful.
The easiest way I can think of testing which is faulty is to loop the output to the EQ back to the input from the EQ. If the sound is still one channel, then the receiver is faulty. If the sound is normal, then it's the EQ. That assumes that the cables are OK.
The next thing is to find the fault. It could just be a faulty solder joint in the sockets, or something electronic and for that you'll need some test equipment and a service manual.

S