Hi Doddy, yes it is a Fotek ac/dc ssr with a switching voltage between 3 and 30v dc, I had it wired to p16c/p16e of bob and when I toggle it on/off in uccnc the led would come on and off.

The ssr was wired to a ac chassis socket to plug kress spindle into, but when the ssr was switched off I measure voltage across the chassis socket pins and was shocked to see I had 246v when it was supposed to be off and in an open state, I even disconnected the dc supply just to make sure it wasn't getting any voltage from the bob and it still showed 246v.
A quick Google search and I discovered that other people have had similar issues with them failing closed unlike a mechanical relay.

Yes I see what you mean now by using onboard relay to control the external relay used to switch ac power so will give that a go and fingers crossed I'll be successful!

Many thanks for your time I'll let you know how I get on.

Cheers

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