Weird problem, anyone got any ideas....
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From: Rod Speed on 12 Feb 2010 05:31 XR8 Sprintless wrote: > On 12/02/2010 7:38 AM, Doug Jewell wrote: > >> 246V shouldn't cause an issue - it is only 2.5% above 240V and a >> tolerance of +/-10% is acceptible on the mains. But if the PSU is >> designed for 220V as many are, it will be seeing a 12% over-voltage, >> which may be enough to shut it down. Have you tried swapping the PSU >> for a completely different brand? This would be what I consider the >> most likely issue. > > Ps designed for 230V Tried 3 different power supplies in the machine > which all work fine in the workshop but fail at customers house. > >> >> Another strong possibility is noisy power. You may be measuring 246V, >> but if there is a lot of noise on the line it may well be spiking >> several hundred volts higher, which would be sufficient to throw a >> PSU into error. Try a good quality power filter (not just a surge >> protector). > > Tried it through a UPS no difference will not turn on. > > >> Other possible causes (admittedly many of them clutching at straws, >> but they do happen): >> >> Check that active & neutral are wired the correct way. Easiest way >> is to measure voltage to ground. N-E should be 0V, A-E should be >> full 240V. (some meters may throw the earth-leakage switch, so be >> careful). If looking at a wall socket, Active is the left-hand hole. > > Used a CABAC tester which reports circuits wired correctly. > >> I assume when you measured the voltage you measured it at the point. >> Try measuring it at the end of the cord. I've seen faulty power >> cords before - did you use a different cord or the same cord when >> you tried at your place? Alternatively, perhaps it is a faulty power >> point / power board that isn't making good contact with the plug on >> the cord? > > Checked the power at the end of the cord. Tried different cords. > > >> You say you have tested with nothing connected - did you start with >> the computer, plug it into the wall then try starting it? or did you >> start with peripherals plugged in then one-by-one unplugging them? >> I've seen peripherals throw an error state that will stop the PSU >> starting, and it then needs to be disconnected from power for a >> while before it will start back. > > Tried with nothing connected first. Then tried new power supply same > result. Eventually got it to work but then it failed again next day. That supports the grounding problem. > It's now up to PS number 3 which all work fine in the workshop even > after 48 hours testing and multiple restarts. > > >> Good luck, and when you do solve it, please report back what you >> found. > > I will. I've just ordered another bigger PSU and a new board for it. > I'm completely out of ideas. Bet its a grounding problem.
From: Marts on 14 Feb 2010 03:05 Rod Speed wrote... > Then I bet its something about the grounding that is fooling the short detection. How does this work? > Since you get the same result with an UPS, I'd try with the ground wire cut > in an extension cord with nothing plugged into the PC at all and fully insulated > from any metal bench etc. Bet it does work fine in that config, and then you > can move on from that to work out where the grounding problem is. That would indicate a faulty GPO, which is easy enough to test with a meter. Didn't the OP say that he tried this?
From: Rod Speed on 14 Feb 2010 03:47 Farts wrote > Rod Speed wrote >> Then I bet its something about the grounding that is fooling the short detection. > How does this work? Every power supply attempts to detect a short on the output of the power supply and shuts down the power supply if it decides that there is a short on the output. >> Since you get the same result with an UPS, I'd try with the ground wire >> cut in an extension cord with nothing plugged into the PC at all and fully >> insulated from any metal bench etc. Bet it does work fine in that config, and >> then you can move on from that to work out where the grounding problem is. > That would indicate a faulty GPO, Not necessarily. > which is easy enough to test with a meter. Not necessarily with the more subtle faults that fool the power supply short detection. > Didn't the OP say that he tried this? Yes, but he clearly doesnt realise that it isnt a definitive test. Look at it the other way, if there is no fault specific to the mains in the house, why does it work fine away from the house, but fails in the house ? Its just a tad unlikely that the problem is bad Fung Shui etc.
From: Doug Jewell on 14 Feb 2010 04:11 Marts wrote: > Rod Speed wrote... > >> Then I bet its something about the grounding that is fooling the short detection. > > How does this work? The chassis of a computer is grounded to earth, and also connected to 0V of the DC supply. So when earth is at a different potential to neutral, currents start to flow in ways they aren't supposed to. The PSU will detect this and shutdown. When a PC triggers an RCD protector, it is often because of a faulty earth in the building, rather than a fault in the PC. > >> Since you get the same result with an UPS, I'd try with the ground wire cut >> in an extension cord with nothing plugged into the PC at all and fully insulated >> from any metal bench etc. Bet it does work fine in that config, and then you >> can move on from that to work out where the grounding problem is. > > That would indicate a faulty GPO, which is easy enough to test with a meter. > > Didn't the OP say that he tried this? I'm not familiar with the specific tester he used, but a lot of the plug-in type testers just use neon's to indicate faults like swapped A-N. Being Neon, they generally won't show an N-E fault unless it is more than about 90V, and in that scenario will often trigger an RCD anyway. Also, under load, the N-E voltage will probably drop anyway. A high-impedance DMM is much more effective for measuring this type of fault. > > -- What is the difference between a duck?
From: Marts on 16 Feb 2010 15:12
Rod Speed wrote... > > If the issue here is whether or not the GPO has a good earth connection, > > That is just one posssibility. What are others? What are we missing here? > > which, going by your guys' views on the PS having a faulty earth detection issue, > > No one ever said that. What, that there is a fault with earth leakage detection? > > then testing voltage from Active to Earth using a > > Fluke or similar quality meter should prove this. > > Pity about the other possibilitys. Which are? > > If it trips the RCD then you know that it's working. > > You dont know that there is one. If it's a new house as the OP implied then it will have one. |