ojc123 Posted October 5, 2012 Author Share Posted October 5, 2012 I've tested the potential difference between the common ground of the Demux and the dimmers. It is fluctuating between 3.5V and 4.0V. The potential difference between the grounds on the dimmers are of the order of 0.02V.Should read The potential difference between the grounds on the dimmers are of the order of 0.2V. Link to comment Share on other sites More sharing options...
dbuckley Posted October 5, 2012 Share Posted October 5, 2012 I've tested the potential difference between the common ground of the Demux and the dimmers. It is fluctuating between 3.5V and 4.0V. The potential difference between the grounds on the dimmers are of the order of 0.02V. The potential difference between the casing of the Demux and the casing of the Dimmers vary between 3V and 4V. The difference between all the dimmer casings is about 0.3V. Are these figures likely to be worth investigating? I need to be able to talk to the sparky like I have a clue. That is the cause of the problem. Given your description of the installation, where both the dimmer supply and the demux supply comes from the same board, the voltage between grounds should be so close to ground it's hard to measure. But you are seeing whole volts. Volts that are a significant fraction of the 10v full output of the demux. First guess - neutral and earth wires crossed over. Before bringing in the sparky, check that there is continuity between the plug earth pin and the chassis of each item. Switch the distro main off, and see if there is still rogue voltages. If you have a Cat. III or better meter, check the resistance between the demux case and the dimmer case with the control cables unplugged but all poweredd. Should be very close to zero ohms. Don't do this with a non-rated meter as it may not like voltages present whilst trying to measure resistance. Unplug everything, and check resistance voltage between the earth pin supplying the dimmer and the earth pin of the demux socket. Link to comment Share on other sites More sharing options...
ojc123 Posted October 5, 2012 Author Share Posted October 5, 2012 First guess - neutral and earth wires crossed over. Before bringing in the sparky, check that there is continuity between the plug earth pin and the chassis of each item. Understood Switch the distro main off, and see if there is still rogue voltages.Understood If you have a Cat. III or better meter, check the resistance between the demux case and the dimmer case with the control cables unplugged but all poweredd. Should be very close to zero ohms. Don't do this with a non-rated meter as it may not like voltages present whilst trying to measure resistance.Understood Unplug everything, and check resistance voltage between the earth pin supplying the dimmer and the earth pin of the demux socket."resistance voltage"? I'm not sure what you mean. Do you mean check both resistance and voltage or is 'resistance voltage' some thing beyond my basic understanding of Ohm's Law. It may be a case of 'If you have to ask don't do it.' Thanks. It may be Monday before I can report back the results. Link to comment Share on other sites More sharing options...
dbuckley Posted October 6, 2012 Share Posted October 6, 2012 Typo, probably induced by using an iPad :). Check the resistance. Also occurs that we best check out own house is order, check the 13a plug on the demux is wired right. The dimmers are hard wired, no on c17 plugs,yaas? Link to comment Share on other sites More sharing options...
ojc123 Posted October 6, 2012 Author Share Posted October 6, 2012 The dimmers are on 32A plugs.Thanks. Link to comment Share on other sites More sharing options...
dbuckley Posted October 6, 2012 Share Posted October 6, 2012 If so then check the wiring of them too. Connectivity from chassis to earth pin should be enough. Link to comment Share on other sites More sharing options...
ojc123 Posted October 11, 2012 Author Share Posted October 11, 2012 Thanks to dbuckley who helped me to interpret a fair number of voltage and resistance readings we've narrowed it down to the demux. Possibly the output capacitors have been fried as suggested. Whether it's a repair or replace I'll reposition it to make sure it can be easily switched off in future.Thanks to all who contributed. Link to comment Share on other sites More sharing options...
keithh Posted October 15, 2012 Share Posted October 15, 2012 Hi Owen, Thank you for the glowing referance, Its nice to know that things are still working well. you were wise to allow us to sort out the instalation it certainaly was unsafe. Re you Demux problem , If you care to give me a ring I will once more attempt to resolve your problem. I agree with the comments that the main smoothing capacitor could be the reason for your unstable output. It is common with electronic equipment after a few years. Once this starts to fail it can introduce a 100 Hz ripple to the DC output This will result in the chase type problems you are having I am now working in Leeds for the Northern Branch of a Major Trade supplier who is based in High Wycombe. I can be contacted on the following numbers:- > 0113 386 9096 < or > 07860 584351 < Any time between 8-00 and 5-00. Monday to Friday With regards to Mick Habergam , He is still around In the industary and should to require has contact information then I can pass this on. Cheers Keith Hartley. Link to comment Share on other sites More sharing options...
Nicktaylor Posted October 15, 2012 Share Posted October 15, 2012 Read this thread with interest. Had to laugh at the last comment though! I am off to a workshop at the southern HQ on Friday! Link to comment Share on other sites More sharing options...
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