Tom Posted July 7, 2021 Share Posted July 7, 2021 Here's a weird one. I have an electric fence energiser plugged in to the caravan's ring main (albeit via a spur extension running outside), it is earthed directly on to the caravan's earth rod. When it is switched on and happily ticking away, our iMac (also plugged in to the ringmain) starts ticking too (in time with the energiser - about 60bpm). The computer works fine and seems otherwise unaffected. Why so? I guess I'll move the earth to a dedicated rod when I get back this eve to see if that solves it, but just curious as to why it should be doing this. Any ideas? Link to comment Share on other sites More sharing options...
DamonHD Posted July 7, 2021 Share Posted July 7, 2021 Protective elements in the iMac power supply absorbing nasties injected into the mains by the electric fence box? You are likely incrementally damaging the iMac and any other electronics (including LEDs) on that supply. I would take one or the other off that supply ASAP, at least temporarily, and get something like a UPS in front of your iMac to take one for the team. Rgds Daon Link to comment Share on other sites More sharing options...
Onoff Posted July 7, 2021 Share Posted July 7, 2021 Try a surge protector on the Mac? Link to comment Share on other sites More sharing options...
dpmiller Posted July 7, 2021 Share Posted July 7, 2021 Mightn't be mains-borne at all. the iMac's audio amplifier may well just be picking it up... Does a battery powered MW radio tick also? 1 Link to comment Share on other sites More sharing options...
Tom Posted July 7, 2021 Author Share Posted July 7, 2021 Thanks all for the suggestions. Will investigate with a radio... Link to comment Share on other sites More sharing options...
Tom Posted July 8, 2021 Author Share Posted July 8, 2021 OK, further observation last night: the iMAC clicks even when it is switched off AND even if the wall socket is switched off (single pole I believe). It stops if you unplug it. So, I'm thinking rsather than a power spike or EM interference thing it must be to do with the earth? Link to comment Share on other sites More sharing options...
ProDave Posted July 8, 2021 Share Posted July 8, 2021 Get one of those clamp on EMC ferirte beads over the mains lead. It sounds like the mains wiring is acting like a big antenna to pick up the interference from the electric fence. While you are at it, have a good look at how the electric fence is set up. How is it earthed, you don't want it earthed to the mains, give it it's own earth rod and have no connection to the mains earth, and an EMC ferrite on the mains lead for the fence energiser as well. 2 Link to comment Share on other sites More sharing options...
Tom Posted July 9, 2021 Author Share Posted July 9, 2021 Thanks all, and thanks Dave. I moved the enrgiser's earth lead to it's own spike and all seems fine now. No more clicking and the children's hair is no longer standing on end. I'll have a look at getting some of those ferrite things - IIRC back in the day they used to be attached to most new electronic gizmos but I think have fizzled out now? I always thought they were snake oil, a bit like those magnetic water softeners. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now