Thanks for getting back to me everyone,
The keyboard is a Kurzweil SP2X. I've emailed their support but as it's the weekend I don't expect a reply for a while.
Basically what is happening is that the pitch control works fine, but the mod wheel is sending a signal randomly, but consistently so, varying from 102 to 118 as far as I can see.
Another strange thing with the mod wheel signal is that once activated it never returns to zero, but stays between a minimum of about 103 to a max of 127 (The max is obviously normal). This has the effect of cutting out all articulations below the then minimum of 103, which is of course most of them.
I have made logic return the setting to zero in preferences/midi/reset messages/controller 1 (modulation) to zero, but of course if I touch the mod wheel or it receives one of these phantom signals I'm stuck back between a cc1 of 103-127.
@Eriksimon: I tried the control changes input filter but the keyboard is still generating a signal which I can see in the transport bar. I'm not sure it the filter kicks in after the signal reaches logic. It seems to, as when I disable the notes option, I can no longer hear the keyboard but the transport bar still shows an incoming signal.
Oh wait...I see, the signal is visible but Logic ignores it with this setting... This would at least enable me to programme the changes in the hyper editor I suppose, without interference from the keyboard, but you're right, it is a pretty blunt tool.
Stopping the phantom signal is my main priority, but I would also love to know how to make the mod wheel respond properly and output a CC1 signal of zero when in the downward position, instead of 100+.
I think the transformer may be the best option for now.
Once again, thanks for your help on this...much appreciated.