Timeline for Short circuit when probing live ATX power supply primary section with voltmeter [closed]
Current License: CC BY-SA 3.0
30 events
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| Feb 5, 2016 at 17:39 | comment | added | Amanda | @Russell McMahon The 2 large filter caps in the primary section are indeed rated for 200V, I measured around 160V DC across them before the fault. The PSU is rated for 230VAC. The exact model is FSP250-60GTV. Unfortunately I could only find the data-sheet, but no schematic diagram. It is based on Power IC KA3511, like the one you linked to in danyk website. Interesting information, thanks. | |
| Feb 3, 2016 at 17:02 | comment | added | Russell McMahon♦ | Many PC power supply ccts here - only 1 appears to be a FSP supply and does not seem to be your one but ccts should be useful. | |
| Feb 3, 2016 at 17:02 | comment | added | Russell McMahon♦ | I'm "worried" by that 470 uF cap which appears to be 200V rated. If it is and depending where it is that suggests it might be a 110 VAC only supply - SO - IS it 230 VAC rated? - if not then it may run for an indefinite period and then self immolate and appear to be related to some action of yours. As you are in UK you'd expect it to be 230 VAC rated. | Your PCB is labelled "FSP Group Inc" - they are a Taiwanese power supply manufacturer. | |
| Feb 3, 2016 at 13:41 | review | Reopen votes | |||
| Feb 8, 2016 at 0:55 | |||||
| Feb 3, 2016 at 9:49 | comment | added | nekomatic | @transistor I would be very interested to hear from anyone who works in a repair workshop on this type of equipment, but I'm going to guess that if their repair workshop stays in business then they know how to make these measurements without damaging either themselves or the equipment under test. | |
| Feb 2, 2016 at 23:23 | vote | accept | Amanda | ||
| Feb 2, 2016 at 22:20 | history | closed |
Ricardo Daniel Grillo PeterJ nidhin Nick Alexeev |
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| Feb 2, 2016 at 19:11 | comment | added | Transistor | Many comments saying that live probing of a mains circuit is dangerous. I don't see any explaining how repair workshops tackle the problem. In many cases the equipment has to be powered up to diagnose a fault - schematic or not. | |
| Feb 2, 2016 at 19:06 | answer | added | Transistor | timeline score: 0 | |
| Feb 2, 2016 at 16:45 | answer | added | Dwayne Reid | timeline score: 1 | |
| Feb 2, 2016 at 16:03 | comment | added | Amanda | @nekomatic I do agree with what you write. And yes, I was holding the two probes with both hands (probing the two pads encircled in red), which is not safe at all. I had spent some time probing around the primary with the meter COM lead at the HOT ground (- of the large filter cap) with no problem at all. The moment I probed those two pads I witnessed the fireworks. I wonder if leaving the COM lead at the hot ground and probing those two pads separately could have prevented the fault. | |
| Feb 2, 2016 at 15:36 | answer | added | WhatRoughBeast | timeline score: 2 | |
| Feb 2, 2016 at 14:57 | comment | added | nekomatic | Also, you describe testing across two points on the PCB - were you holding one probe in each hand to do this? It's much, much, much safer to make a connection to one point using e.g. a test hook or crocodile clip, that will stay where you connected it, before touching the other probe to the other point - so there's no risk of taking a shock across your heart. | |
| Feb 2, 2016 at 14:43 | comment | added | nekomatic | It's not about "courage", "daring" or "exploring": mains-powered switch-mode power supplies contain capacitors charged to high DC voltages and these really can kill you - irrespective of RCD protection, use of an isolation transformer, etc etc. If you want an analogy, would it be "courageous" of a learner driver to head out on the motorway the first time they got behind the wheel? To learn about switch-mode power supplies how about investigating a DC-DC converter. Make your mistakes on something less hazardous. | |
| Feb 2, 2016 at 14:22 | comment | added | Amanda | I posted this request for help because, to me, the mistake I made is not obvious. From some of the judgemental comments I read above my mistake seems to have dared to probe a high voltage area. While I have read books and many interesting posts in this forum about power supplies, how am I supposed to learn if I do not take the courage to experiment? Far from being reckless, I think that the only way to learn is through direct experience. | |
| Feb 2, 2016 at 14:20 | comment | added | Amanda | @Russell McMahon. The meter was on high range volts DC and it's still working fine (as very little current is drawn owing to the high input impedance, if I am not mistaken). It's a Brymen BM257 (1kV cat II, 300V cat IV). I'm in the UK, so mains is 230VAC. While I am no expert, I am very conscious of the beginner's fatal mistakes when using a DMM to probe mains. What do you mean by "orientation of the parts"? | |
| Feb 2, 2016 at 13:25 | comment | added | Russell McMahon♦ | Is your meter still working? Was it on ACV or DCV on a suitably high range. What was its certified working voltage? I assume you are using 110 VAC mains as large cap is labelled 200V 470 uF. IF meter broke down it can cause short and excitement but this would usually be obvious afterwards. If meter was not on HV Volts or if eg positive lead was in 10A socket "things can happen". No obvious action NOT caused by a fault condition applied by you seems likely. | |
| Feb 2, 2016 at 13:18 | comment | added | Russell McMahon♦ | It is almost certain that you caused a short circuit. You do not say what the orientation of the parts was - maybe as shown, maybe not. Sometimes it is possible to nudge something unconnected while making a measurement with interesting results. The white/black wiring and choke suggest that that has AC mains on it . Ignore the rude comments. Learn from any good advice - whether from rude people or others :-) | |
| Feb 2, 2016 at 12:31 | comment | added | Ecnerwal | "Hi-pot" means the part passed high voltage potential testing - it is not a part label. | |
| Feb 2, 2016 at 12:25 | comment | added | Ecnerwal | Courage is handy for getting dead, especially when fortified by ignorance and blended with high voltage. Recognizing when you are a user or not (in the "no user servicable parts inside" sense) is one of those things that helps to keep you alive - or not. | |
| Feb 2, 2016 at 12:05 | comment | added | user98732 | [Hate that length limit...] I have much more respect for someone who goes exploring without a map than someone who only goes where they are "supposed" to go, and who attacks others for having the courage they lack. | |
| Feb 2, 2016 at 12:04 | comment | added | Passerby | If we assume you didn't short something out with your probes, maybe you caused an unforseen feedback failure, and instead of failing safe, it overloaded the part by attempting to over correct what it saw as a short. | |
| Feb 2, 2016 at 12:04 | comment | added | user98732 | @Andyaka, I won't say quite the same thing to you, because I don't think you've been quite so rude in your approach, but I will say that I think you are very wrong in your attitude and in your conclusion. There is much to be gained by poking around. There is even much to be learned by blowing things up, as long as you live to benefit from the knowledge. Speaking of the old days of vivisection, my experience is that there was much more danger in working around many hundred volt B+ supplies in vacuum tube equipment than even today's line-powered computer supplies. | |
| Feb 2, 2016 at 11:57 | answer | added | user98732 | timeline score: 2 | |
| Feb 2, 2016 at 11:56 | comment | added | Andy aka | @Entropivore then you are going to have to say the same to me. No schematic, no understanding, no recognition of what certain components do = nothing to be gained by poking around. This type of poking around may have been useful in the early days of vivisection but there was little risk of electrocution. | |
| Feb 2, 2016 at 11:40 | review | Close votes | |||
| Feb 2, 2016 at 22:20 | |||||
| Feb 2, 2016 at 11:34 | comment | added | user98732 | @FakeMoustache, telling someone not to try to fix a piece of equipment is not a useful response and just contributes to the "just leave it to the experts" mentality of ignorance and helplessness. Your comment, "...a power supply you should not even be poking around in..." is rude and patronizing. I would encourage the OP to pay no attention to you. | |
| Feb 2, 2016 at 11:12 | comment | added | Bimpelrekkie | You ask questions about an ATX power supply. You poke around in it while it is LIVE. Then it goes BANG and you're surprised ???? Geez ! If you need to ask questions about a power supply you should not even be poking around in it let alone a LIVE one. First educate yourself then so you would learn why not to open them. And yes of course you made a short, you were obviously not careful enough despite what you write. | |
| Feb 2, 2016 at 11:05 | review | First posts | |||
| Feb 2, 2016 at 11:27 | |||||
| Feb 2, 2016 at 11:03 | history | asked | Amanda | CC BY-SA 3.0 |