Roger,
I had a similar problem recently.
With Maix, or CCDSoft, (whatever you use, I use Maxim) try the "Move" command. I set about 3 seconds, and id you look through the grill on the back, you should see one of four LEDs light when you move in RA/X RA/Y, and Dec/X Dec/Y. The LED should light if the command is getting to the camera. You don't need the guide cable for this, just the power, and USB plugged into the camera. If all goes well there, the next thing is to try the resistance on the camera auto-guider plug, with a multi-meter.
I will dig out the pins, and what they represent. Shoot me an e mail and we can do this off group, at
g.beal@xnet.co.nz
Gary