Andy wrote:
Is there any where here in the UK that will repair this coupler?

I have repaired mine a couple of times. The SGC documentation
is very good. Have you checked the four lines between the
Smartlock and the SGC-230? If the notune line (white wire)
is at ground, the tuner is in perpetual reset. The notune
line should be at a plus voltage when the reset button
is not pushed and go to ground when the reset button is
pushed. The digital control portion of the tuner is super
easy to troubleshoot and a good technician should be able
to diagnose and repair minor problems. All of my problems
have been minor and easy to repair.

The most nagging problem was when the tuner wouldn't tune
while my pickup was in motion but would tune just as soon
as I stopped the vehicle. It was a loose nut inside
the box on the output feedthrough insulator.

Have you tried the tuner without Smartlock in the circuit?
--
73, Cecil http://www.w5dxp.com