Seeburg HF100G - Selections

My HF100G won't select B2, D2, F2, H2 and K2, all other selections work okay.
I figure these 5 selection must run from/to a single faulty cable, but I'm not very good at reading schematics and there are no obvious faults on the back of the selector unit.
I was wondering if anyone knew exactly which wire(s) I should be looking at, or the area most likely to cause this fault.

Keith,
Usually, that problem is in the "plugs"--try connecting the SA Unit and the ES together, and see if it solves it--If so, clean up the Jones plugs--if not, look at the wires under the cover(s)--pin #2 is for the 2's-- Ron Rich

Thanks Ron,

Connecting the SA and ES together did fix the problem.

I know this will be a stupid question, but why do the SA and ES have to be plugged into the Selection Receiver if they work by just connecting them together?

I haven't found the "actual" fault yet. Next I am going to clean the sockets on the Selection Receiver and then look for bad wires if that doesn't work.

Hi Keith,
Plug them back in "the right way", again---bet they will work--
Quick answer--they don't ! --longer answer--unless you are using the stepper, as that's how a wallbox connects to the SAU----
Ron Rich

Yes Ron, after cleaning the sockets the problem is fixed. Thank you.