Total novice and lost

[sfallan]

Morning all,

I have a multi meter to hand and guidance on what i need test and how to test it would be apprecaited.

With regards the cable, there are 2, one connected to the PCB then one connected to that, an extension cable. This is due to the configuration of the box. I can try connecting direct without the extension.

How would I test the cable as being 1:1, I purchased the one suggested by a member here however the one in the box was already there (found it when I opened up)