Grounding old equipment - Page 1
Forum section: electronics / beginners

author: John B
author_rank: Frequent Contributor
timestamp: July 28, 2017, 01:38:10 am
content: Here's a stereo that I am repairing. Looks like 1990's stuff? Anyhow, one thing that surprised me is that the outer shell is metal, yet it only has a 2 prong plug, no ground. As you can see from the picture, the mains wiring sits rather close to part of the metal chassis. The earth on the RCA inputs and the earth on the headphone socket all connect to the chassis, so even if you cannot reach the metal chassis, there's still a few common human contact areas that could be a shock hazard. I get the heebie-jeebies just looking at. Is there a reason why I shouldn't ground the metal chassis with a 3 prong lead, and why wasn't it done by design in the first place?

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: July 28, 2017, 04:04:13 am
content: not it is not very safe. doesn't satisfy class I or class II insulation requirements.see this threadhttps://www.eevblog.com/forum/projects/audio-grounding-xlr/alsohttps://en.wikipedia.org/wiki/Appliance_classesIt would be ok if yougroundconnect the chassis to protective earth but depending on what is connected and how it is connected internally you could end up with ground loops.edit:oops Noticed I had used ambiguous wording.

author: WastelandTek
author_rank: Frequent Contributor
timestamp: July 28, 2017, 04:09:25 am
content: kids these days, we used to run AA5 radios with nonpolarized plugs and we only got shocked once in a while geeezzzyeah, that's pretty ghetto by modern standards

author: Electro Detective
author_rank: Super Contributor
timestamp: July 28, 2017, 06:08:14 am
content: yeah, a lot of 240 volt 50 hz two prong video recorders and DVD players were/are good like that.You get a nice tingle from the metal when moving them about in a cabinet if they are still plugged into the mains and or TV antenna cableOnce they are hooked up with other gear via RCA cords, no tingle, no problem,even if all the gear is 2 prong poweredI assume all those combined 'floating' neutrals and chassis vote they are part of the Neutral/Earth/Ground link at the electrical switchboard, and settle downIf any one of a group of devices does come standard with a earth/ground 3rd prong, all the others connected via RCA cords get magically earth/grounded by the combined RCA shields AFAIKThe main concern with two prong gear is to ensure the Active wire going into the device is connected to the internal FUSE, not the neutral.

author: capt bullshot
author_rank: Super Contributor
timestamp: July 28, 2017, 06:45:10 am
content: Don't ground it.Grounding the chassis places all kind of ground loops on the system, resulting in line frequency hum.These things were designed to work this way and to be safe according to the standards that were active then. They aren't getting unsafe over time, it's the standards that change, if you build such things from scratch today, it would look different, but still won't have a grounded chassis. As long as you do your leakage current and isolation properly, there's no reason to ground a chassis today and wasn't back then. The isolation and leakage was done properly back then is still okay for todays usage.

author: Zero999
author_rank: Super Contributor
timestamp: July 28, 2017, 08:10:26 am
content: Quote from: Electro Detective on July 28, 2017, 06:08:14 amThe appliances that gave you that tingle probably have a switched mode power supply. The leakage across the Y capacitors can give you a tingle. Normally it's not an issue but if several appliances are connected together or their chassis touch, it can become more of a safety hazard, as the leakage currents add together.The device shown in the original post, appears to have mains frequency transformers, which leak far less current than an SMPS with Y capacitors bridging the mains and output.Quote from: HackedFridgeMagnet on July 28, 2017, 04:04:13 amI don't think there's enough information to come to that conclusion. We don't know where the mains tracks are on the other side of the board or the creepage and clearances between them and the case/secondary.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: July 28, 2017, 08:20:31 am
content: Quote from: Hero999 on July 28, 2017, 08:10:26 amWas just going off the fact that there is only one layer of insulation and they put two layers on any two wire mains these days. No doubt to get a compliance badge.That said I probably have an amp done to a similar standard very close to me now and am not about to change it.

author: John B
author_rank: Frequent Contributor
timestamp: July 28, 2017, 09:16:28 am
content: The unit does use a pair of transformers (one switched for low power standby). But before the isolating transformers, the posts that the mains wire are soldered to go through the board and out the other side. So there is about 8mm of clearance between the flimsy, flexible chassis and the wires straight from the wall. I suppose it hasn't killed anyone yet...but still.

author: RGB255_0_0
author_rank: Frequent Contributor
timestamp: July 28, 2017, 10:06:24 am
content: Quote from: John B on July 28, 2017, 09:16:28 amMaybe if it gets dropped or kicked it would be a concern. Maybe have the cable routed underneath but that doesn't look possible to solder that way. As a compromise, put some Kapton tape directly below the mains connection joint.

author: Nusa
author_rank: Super Contributor
timestamp: July 28, 2017, 10:09:43 am
content: The stamped steel I see in the picture is not nearly as flexible or fragile as you imply. You'd literally need to use a hammer or beat the unit against a rock to compromise theassembledcase enough to contact the AC input.

author: RGB255_0_0
author_rank: Frequent Contributor
timestamp: July 28, 2017, 10:12:09 am
content: Delivery drivers have strong boots.In any case, it'd be a couple of minutes to add some kind of insulating sheet there if you were inclined to worry about it.

author: Zero999
author_rank: Super Contributor
timestamp: July 28, 2017, 12:24:41 pm
content: Quote from: HackedFridgeMagnet on July 28, 2017, 08:20:31 amThere are two layers of insulation on the mains cable: the black over jacket on top of the brown and blue insulation on the two cores.

author: b_force
author_rank: Super Contributor
timestamp: July 28, 2017, 12:56:59 pm
content: Quote from: capt bullshot on July 28, 2017, 06:45:10 amI agree with this!Worked on a lot of audio gear and as long as the clearances/creepage is good enough, the product is safe.In fact, most gear from the 80's/90's is totally safe.It's only the super old tube amplifiers which didn't had a isolation transformer.

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 28, 2017, 01:08:32 pm
content: Quote from: capt bullshot on July 28, 2017, 06:45:10 amI disagree with this!If you can't fix a ground loop problem, you don't belong in this forum. But none of us (even the physicians) can fix electrocution.

author: b_force
author_rank: Super Contributor
timestamp: July 28, 2017, 02:00:32 pm
content: Quote from: Richard Crowley on July 28, 2017, 01:08:32 pmSince when is not-grounding equal to electrocution?In fact, as far as I know, most audio gear, especially CD-players etc, are never grounded.

author: RGB255_0_0
author_rank: Frequent Contributor
timestamp: July 28, 2017, 02:13:58 pm
content: As said before though, the likelihood is eventually the ungrounded equipment does end up grounded; via HDMI and so forth to the TV or receiver.What I don't like is figure of eight plugs because you have no control whether the fuse is live or neutral (pedant: yes ok after bridge...). Should move to Mickey Mouse plug and just ground equipment properly.

author: Gyro
author_rank: Super Contributor
timestamp: July 28, 2017, 06:31:22 pm
content: Quote from: Hero999 on July 28, 2017, 12:24:41 pmI'm uncomfortable with what they've done with the mains cable termination, there's obviously been some cost cutting.The normal termination for mains cables in Class II products I've designed is for the cable to be crimped into a touchproof 2 pin socket which plugs onto the header on the PSU. Exposed inner cores (single insulation) are covered in heatshrink to maintain double insulation all the way to the crimps in the connector. The mains cable length inside the case is also minimised so that, in the unlikely event of the connector becoming unplugged, it can't contact secondary side components or chassis.Now if you look at the photo, the mains input header is in place but the inner cores are soldered directly to the pins, there's no secondary insulation on the inner cores and the cable connection point results in quite a lot of cable inside the case. It's pretty unlikely that both cores would become unsoldered - unless maybe a fatigue problem caused by the cable flapping about, or a badly soldered repair, but if it did, then you have the possibility of the live conductor contacting the case. At least the inner core length has been kept to a minimum.I'm not sure, off hand, whether this arrangement would pass approval, but at minimum, I would want to add some mechanical tie-down of the cable to the board. This should be close enough to the termination to prevent the cores touching the chassis on joint failure.The choice of SRBP for the PCB is normally a dodgy one as it is mechanically brittle and can break away at the mounting points. cem-1 is more appropriate. It's forgivable in this case because the heavy components are screwed to the case, providing additional support. It has obviously heen through the value engineering mill though.P.S. It's not the delivery driver's boots you need to worry about, it's the crane driver dropping the shipping container on the dock. I've seen cases where the bottom 2-3 box layers have become 'sacrificial'! It's normal for OEMs to ship 5-10% (negotiated) to distributors for spares.

author: tronde
author_rank: Frequent Contributor
timestamp: July 28, 2017, 06:45:29 pm
content: I never stop being puzzled about electronics people and their fear for mains voltage. We are talking about maximum 250 volts. It's not kilovolts. Some of you do really need to get some realism into this.This is a stereo. It's meant for a normal domestic environment, i.e. no excessive humidity or dust. It is not ment to be mechanically abused as power tools are.According to European regulations, this kind of equipment will need at least4mm of clearanceand at least5mm of creepagebetween mains voltage and "exposed parts". That is basically anything a user can touch.The term "double insulated" does not necessarily mean "two layers of insulation". It means the insulation should give the same level of protection.A normal Class-II equipment is allowed to leak 0.25mA, and if they use Y1 capacitors between each mains wire and 0V out as they often do on smaller chargers, this can be felt as a light shock.The only suspect thing I can see here, is the same as Gyro mention; the mains wires should be tied to the PCB, but this was not normal back then, and it is not a big safety risk when the stereo is used as expected.

author: RGB255_0_0
author_rank: Frequent Contributor
timestamp: July 28, 2017, 06:55:15 pm
content: Quote from: tronde on July 28, 2017, 06:45:29 pmRealism is that 250VAC indiscriminately kills. I think your sentence is dangerous in itself as newcomers may read it and then we're reading another thread about someone dying as a result of ignorance or negligence.

author: Gyro
author_rank: Super Contributor
timestamp: July 28, 2017, 07:00:23 pm
content: Quote from: tronde on July 28, 2017, 06:45:29 pmAs I alluded to in my last post, this type of consumer equipment has a pretty easy life in domestic use. The problem is getting it to the customer still sufficiently safe that it doesn't immediately try to kill him. Also to ensure that it remains safe during it's operational life (thermal, component, insulation degredation etc.)Edit: and yes 240V AC will quite happily kill you under the right circumstances!

author: floobydust
author_rank: Super Contributor
timestamp: July 28, 2017, 07:01:34 pm
content: OP's stereo, I wonder if it has any decent safety approvals in the first place.That mains power cable, I recognize as a chinese special- I've never seen on a product with real safety approvals like UL/CSA.Sure the wire's insulation can have UL/CSA written on it but as a power cable, it's a fail.There are tug, abrasion, crush requirements for mains cables. Look at every one in your house and they have thicker jackets.I saw it once on a Walmart DVD player, which only had "special inspection" stickers for safety agency. This is basically a hi-pot test.

author: tronde
author_rank: Frequent Contributor
timestamp: July 28, 2017, 07:04:44 pm
content: Quote from: RGB255_0_0 on July 28, 2017, 06:55:15 pmNo, people must get realism into this. Confirm the regulations.4mm clearance and 5mm creepage.This is for reinforced insulation. Normal insulation is half of that.4 or 5mm is not much, but the most stringent regulations says it is enough.

author: Gyro
author_rank: Super Contributor
timestamp: July 28, 2017, 07:11:33 pm
content: A self-respecting engineer designs for 8mmminimum. That includes board flex during mechanical shock too. Just because it's consumer doesn't mean that some prat isn't going to drop it while plugged in!EDIT: Another point is that you aren't just designing one item - you are designing many (my highest volume Class II product shipped 60k/month). That really gets one in a million type problems, hamfisted operators... crane drivers stacking up against you.

author: RGB255_0_0
author_rank: Frequent Contributor
timestamp: July 28, 2017, 07:15:23 pm
content: Quote from: tronde on July 28, 2017, 07:04:44 pmIt's not that part I find abrasive. You wrote something I felt as badly worded and could easily be taken out of context.

author: tronde
author_rank: Frequent Contributor
timestamp: July 28, 2017, 07:16:25 pm
content: Quote from: floobydust on July 28, 2017, 07:01:34 pmThe cable is perfectly normal. In Europe it is today usually known as SKX or H03VVH2-F. It is 2 x 0,75 mm².

author: tronde
author_rank: Frequent Contributor
timestamp: July 28, 2017, 07:29:31 pm
content: Quote from: RGB255_0_0 on July 28, 2017, 07:15:23 pmMaybe you find it badly worded, but I do really mean people must get realistic about mains voltages. Some people on this forum seems to believe that mains voltage will jump out of the socket and bite you in your nose. It will not. When people act based on fear, they will make a lot more errors than if they act based on understanding. The absolute worst thing we can do is to scaremonger. Scaremongering will hide the real danger. We give beginners the feeling that they almost will get killed if they dare to look at mains, but we forget to tell them that a charged 12V car battery can be at least as dangerous in real life.The original question was if this amplifier was safe or not. Many of the answers claimed it was dangerous. The only visible error is the one Gyro mentioned; lack of cable ties. The rest is most likely correct according to both prebious and current regulations. That is why I claim some must get realism into this.

author: hermit
author_rank: Frequent Contributor
timestamp: July 28, 2017, 10:48:25 pm
content: If you alter the design and something happens then it is ON YOU. Be very careful about altering a manufactures design. You may be right that it was poorly done. Doesn't matter. You alter it, the blame falls on you when something goes wrong. You need a legal staff better than the manufactures (if they are even still in business) to prove otherwise. Remember, there is right, wrong and legal. All very different things.

author: Electro Detective
author_rank: Super Contributor
timestamp: July 28, 2017, 11:10:12 pm
content: I'm with hermit and Tronde on this,too much freaking outthat one dumbass numbskull amongst billionsis going to score a unit that has been squashed flat by a shipping container mishap, or a lead foot delivery clown,ignore the tell tale obvious signs of damage,plug into the mains and switch it on with bare feet standing on a concrete floor,grasp the unit tightly, and zap themselves into Hi-Fi HadesFWIW, I've opened and serviced hundreds, no.. thousands of domestic A/V (and professional) units like this, mostly constructed the same or very similarBesides the usual PSU repair, dry/dead pot n switch snafus,and those intermittent ball breakers we all love,IIRC none have ever been or had a power related safety concern.Up till a few years ago that 'thin' 2 core mains cable was/is usually flexible high quality copper,the nylon/plastic retainer gland on the chassis does its job well, and difficult to remove 'by accident' that's for sure.Yes, an internal cable tie wouldn't hurt, been doing that for years, and doesn't send the tech to the poor houseIf you're really freaked about it, or the unit is to be moved about regularly,put some electrical tape under the board across the 240 volt solder points, slide some heatshrink or scrap tubing over the 2 posts,and source clear fuse covers,fill the entire unit with a few tubes of silicone rubberand so forthi.e. I wouldn't bother mate, check the solder points and cable tie the cord down if you like, close it up,"Nurse, send in the next sick patient please..."

author: b_force
author_rank: Super Contributor
timestamp: July 29, 2017, 12:17:48 am
content: Quote from: Gyro on July 28, 2017, 07:00:23 pmSo does a 9V battery!!!!!!!Like the post before, all this equipment past the proper safety tests.That's end of the story.I really don't get this extremely absurd anxious fear horror stories, based on anything except logical sense and science.Go read on papers, mains power doesn't kill an human being on normal conditions.It may hurt, yes. But that's absolutely not close to actually killing someone.People say that it does, simply don't base their arguments on science.And more, don't understand a little thing about clearance, creapage and likeliness of risk.If you're so super weird about safety, simply add a plastic sheet between the boards with mains on it.Than you even are pretty much equal to call your device "double insulated"(Because that's how 90% of the TV's nowadays are made)

author: b_force
author_rank: Super Contributor
timestamp: July 29, 2017, 12:26:44 am
content: Quote from: tronde on July 28, 2017, 07:29:31 pmThis reply should be a sticky, with capital letters and send to everyone on a daily basis

author: tpowell1830
author_rank: Frequent Contributor
timestamp: July 29, 2017, 01:14:45 am
content: The unit has been around since 1990 and is still in one piece... just saying.

author: Electro Detective
author_rank: Super Contributor
timestamp: July 29, 2017, 02:59:57 am
content: Quote from: tpowell1830 on July 29, 2017, 01:14:45 amSame deal for the owner/s of posted unit, and their pets

author: Gyro
author_rank: Super Contributor
timestamp: July 29, 2017, 10:07:26 am
content: @Electro Detective, b-force,I suspect some of that was aimed at me. I was simply looking at that mains termination from a volume manufacturing [Edit:perspective]. I was (and still am) unsure whether that would pass approval, it may well have been a cost reduction introduced some time after the golden sample was submitted. I wasn't saying that this particular sample was about to kill the OP or his cousin - although I would check the condition of the solder joints and ensure that the ends of the wires haven't fatigued as a result of solder wicking up the strands, combined with flapping about over the years.@Electro Detective:When designing volume products (especially consumer!), yes you do unfortunately need to be a little paranoid about killing idiots (even if you would rather like to target a few). It's not the same as repairing them. If the shit hits the fan then it's you, as the design authority that gets it in the neck. Apart from that, designing stuff that flies too close to the wind may result in a compliance fail in some country, requiring design changes, re-submission, lost time and sales revenue. It's just not worth it not to do it to the letter. If the shit does hit the fan, it's the phone charge in the bath dumbass or whatever, those are the stories that make the news, then the nay-sayers will be the first to condemn you, that's just going with the flow of mob mentality. Speaking of which...@b-force:I sugest you go back and re-read your post and look at the incoherent drivel you wrote!... "So does a 9V battery!!!!!!!" - WTF? "It may hurt, yes. But that's absolutely not close to actually killing someone. " - Moron! The only vaguely inteligent thing you said was "plastic sheet" which is often employed my manufacturers to reinforce insulation when space is too tight for straight clearance. The purpose of posting on technical forums is to add value. If you can't say anything coherent, or add any value then it's best that you don't polute threads.

author: b_force
author_rank: Super Contributor
timestamp: July 29, 2017, 11:22:36 am
content: Quote from: Gyro on July 29, 2017, 10:07:26 amBack to physics class maybe?Yes, a 9V battery CAN kill people.It's about the current people, not the voltage.And with all the respect, but I am trying to add some sense to people liketrondedid in his reply.Because the whole useless response about that people are getting killed and safety is really getting on my nerves.That is information not based on any scientific evidence but just some bizarre anxious fear about absolutely nothing.Once again, mains power doesn't kill anyone under normal conditions (unless you really have a weak heart or some other problems).On top of that you need to hit this amplifier with an hammer to even get direct contact to the mains or magically the wires would come off all of a sudden.Guess some people never worked here with older (tube) amplifiers and never dived into papers how safety regulations have been evolved.

author: Gyro
author_rank: Super Contributor
timestamp: July 29, 2017, 11:41:00 am
content: So you're arguing that"Yes, a 9V battery CAN kill people."at the same time as stating"It may hurt, yes. But that's absolutely not close to actually killing someone."about 240V AC mains.What kind of perverse argument is that? Yes of course it's the current that kills, You're going to have a hell of a lot more trouble forcing a lethal current through a human body with a 9V battery supply than with a 240V mains supply. [Edit: Also consider that AC is way more likely to cause cardiac fibrilation than DC.]To take a common exaple here - people complaining that they get a small shock when the plug a connector into an SMPS powered equipment due to minimal Y cap leakage. Now try the same thing with a faulty actually live chassis, a grounded metal RCA jack, in a confined space in an A/V cabinet, with the resulting slightly sweaty hands. A common situation and quite likely to produce a fatal, across the chest, shock if the cabinet becomes live. Now compare that with your 9V battery!You are doing absolutely nothing to make me revise my opinion of your comments!...and yes I have designed and built a valve amp.

author: b_force
author_rank: Super Contributor
timestamp: July 29, 2017, 12:04:20 pm
content: Quote from: Gyro on July 29, 2017, 11:41:00 amNo, what I am doing is that people actually respond with reasonable examples and context.Just saying that by default something is lethal (the post I responded to with the battery) is totally useless without context.Therefor I say, a 9V battery can also be lethal. Just depends on the situation.So this example of yours actually adds a lot more information to all of this.Although, I still find it very unlikely that this situation would be seriously fatal, unless you're laying with your naked chest on the chassis and are bare feet.I also don't see how this would be perverse?You can kill or injure yourself a lot easier with an hammer or chisel.And yes, sometimes that happens, it hurts no big deal.But if we follow the same (illogical) ideas, are we gonna prohibit and ban these tools as well?In fact if I follow the thoughts of some people on this forum, these tools would be straight out of hell and it would be more than irresponsible to even use them.Only used by sick minded people, even looking at them even is dangerous.

author: Zero999
author_rank: Super Contributor
timestamp: July 29, 2017, 12:06:02 pm
content: Yes, a 9V battery can kill you, if you stick needles into your chest, near the heart, and connect them to either terminal of the battery, or if you connect it to a boost converter and charge a large capacitor to hundreds of volts.There's even a bullshit story somewhere online about someone dying because they were playing the sharp probes on an old meter and got electrocuted. It's nonsense. There's no proof that it really happened.

author: Gyro
author_rank: Super Contributor
timestamp: July 29, 2017, 12:25:00 pm
content: Quote from: b_force on July 29, 2017, 12:04:20 pmIf you check back to the actual phrase that you quoted and responded to so incoherently to in your post, it was:QuoteI don't call that a default statement that something is lethal and it certainly doesn't justify your:QuoteAs I advised you, you need to go back and read the drivel that you wrote.

author: ebastler
author_rank: Super Contributor
timestamp: July 29, 2017, 12:27:07 pm
content: Quote from: b_force on July 29, 2017, 12:17:48 amI don't think I have seen it mentioned elsewhere in this thread:Looking at the OP's photo in the first post, isn't that a sheet of black plastic, attached right below the mains-carrying PCB?So all is well: There is an ample air gap plus an insulating layer. No need to modify the equipment, in my book.https://www.eevblog.com/forum/beginners/grounding-old-equipment/?action=dlattach;attach=335835;image

author: RGB255_0_0
author_rank: Frequent Contributor
timestamp: July 29, 2017, 12:32:00 pm
content: I seemed to have started, or helped start, an argument.My quarrel was with the "I never stop being puzzled about electronics people and their fear for mains voltage." It's like saying you can have a lackadaisical attitude to mains.I fear with comments like that people googling and finding this forum as a newbie should be comfortable playing with it. "She'll be alright". That's not an example we should set.

author: RGB255_0_0
author_rank: Frequent Contributor
timestamp: July 29, 2017, 12:33:03 pm
content: Quote from: ebastler on July 29, 2017, 12:27:07 pmLooks like shadow to me.

author: Gyro
author_rank: Super Contributor
timestamp: July 29, 2017, 12:35:33 pm
content: Quote from: ebastler on July 29, 2017, 12:27:07 pmI agree (although I'm not confident that I can see the plastic sheet). The clearances look fine to me. As I mentioned earlier, I would simply check that the mains lead connections are still secure and haven't fatigued due to solder wicking.

author: ebastler
author_rank: Super Contributor
timestamp: July 29, 2017, 12:42:29 pm
content: Quote from: RGB255_0_0 on July 29, 2017, 12:33:03 pmHmm, you might be right, although I don't see such sharp shadows elsewhere in the photo. Also, looking in the area near the "bump" in the baseplate which supports the PCB, it looks more like a sheet being pressed a bit closer to the PCB vs. a shadow following the contours of the bump?From my expereince with audio equipment from the 80s I would expect to see a plastic sheet there. Maybe the OP can check and comment?

author: RGB255_0_0
author_rank: Frequent Contributor
timestamp: July 29, 2017, 12:46:07 pm
content: The shadow matches the angle of the cables, particularly the white one. The light is probably directly above.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 29, 2017, 12:47:56 pm
content: At enough speed a 9 V battery and even a AAA cell can kill, but just from the electricity it is hard. The lowest voltage electrocution I heard of was with a 12 V (14 V) car battery. Even with 240 V most shocks don't kill, but they can.Today with GFIs on most outlets even touching mains wires is usually not deadly, but there is still a small chance and it definitely hurts.Usually the bigger danger with electricity is from causing a fire than from electrocution. So the 115 V in the US also have a downside. So the good thing is there seem to be fuses inside.With audio equipment class II insulation is common. However the amplifier shown does not look like it fully conforms the current regulations. The cable looks like only soldered to the board and would need some kind of cable tie. Also the board might flex on external forces or just slightly dropping it. So some extra insulation toward the case might be a good idea. I don't like the relatively heavy transformer on the what looks like phenolic board - this could break earlier than expected and unnoticed from the outside.

author: Gyro
author_rank: Super Contributor
timestamp: July 29, 2017, 12:55:20 pm
content: Just to complete my response...Quote from: b_force on July 29, 2017, 12:04:20 pmI disagree, live case grasped in one hand with earthed connector grasped in the other. Muscle contraction caused by AC current preventing relase of grip. Confined space. I think there is a significant [Edit: not definite] chance of a fatal shock.QuoteThe big difference is that if you injure yourself with a hammer and chisel, then you did it to yourself by your own stupidty and it is probably non-fatal. There is all the difference in the world between this and being electrocuted by a piece of manufactured consumer equipment whilst innocently performing a task. This is where you are reliant on the designer and the manufacturing line having done the right thing and designed to mitigate risk - call that paranoid if you wish, I call it responsible engineering!QuoteOnly sick minded people deny risk where quantifiable risk exists. Health minded people are aware of risks and mitigate them - be it in designing consumer equipment or using hand tools!

author: Zero999
author_rank: Super Contributor
timestamp: July 29, 2017, 12:59:56 pm
content: Yes, it looks more like a shadow, than a piece of plastic on the case. There might be a piece of plastic fixed to the underside of the board.There's nearly always a flame war, when the subject of safety is raised. Regulations vary over the world and everyone has differing views on what level of risk is acceptable.

author: BBBbbb
author_rank: Unknown
timestamp: July 29, 2017, 01:30:21 pm
content: People bath with the extension cord floating, and you are arguing if there is a chance that this might hurt someone from the general public. Why not ban the electricity all together, we cannot save them from themselves anyway.

author: ebastler
author_rank: Super Contributor
timestamp: July 29, 2017, 02:30:54 pm
content: Quote from: BBBbbb on July 29, 2017, 01:30:21 pmNothing better than a measured, well-balanced response to steer this thread back on track...

author: b_force
author_rank: Super Contributor
timestamp: July 29, 2017, 03:57:03 pm
content: Quote from: RGB255_0_0 on July 29, 2017, 12:32:00 pmOnes again, it's about the context.Newbies should understand the WHOLE context.People don't learn anything from bald statements, that's why I gave the example about tools.Mains power under normal conditions isn't deadly lethal, that's a simple fact, everyone who works with power supplies, amplifiers or electricity can confirm that.(otherwise me and a lot of my colleagues, friends and other people I know would be already dead for half a billion times)Just dive into how many people per year get a shock and how many people die from it.I am 100% sure that crossing the street is far more dangerous (and that's also something I don't have control over if you want to use that argument)The message should be, if you're not confident working with these kind of voltages and/or current levels,simply don't.The second message is, respect nature laws. Which means, if the conditions are right (or wrong rather), you may cause a potential dangerous situation.Although it's not very likely, there could be some fatal risks involved.Third, electronics and water together is a very bad idea.Fourth, make sure you always have a way out/a way to get to a safe distance, safe switch etc when things go wrong.In addition to that, most fatal injuries with electricity areNOTabout the shock itself, but the scare reactions/reflexes so people fall off a ladder, kick their equipment away or do other weird stuff.I am sorry, but ALL examples people gave me so far (over the last 20 or so years) are far fetched and far from normal conditions.Normal working conditions are that some equipment (like the amplifier) is just standing in the TV stand.The ONLY risks of live wire getting contact with the chassis is when the wires will break off or when the chassis is heavily damaged (dented).In the last case, the user isn't allowed to use the product anymore (and shouldn't)The first case is EXTREMELY unlikely if you look how the live wires are wrapped AND soldered on the board.Also, this amp passed a reasonable safety test. Yes, it's a little old, but back than the rules were pretty ok.So, with all the respect, but with all my knowledge and experience I really don't see all the paranoia.That's the last thing I am going to say about it.

author: tronde
author_rank: Frequent Contributor
timestamp: July 29, 2017, 04:02:53 pm
content: Quote from: RGB255_0_0 on July 29, 2017, 12:32:00 pmSince this obviously is aimed at me:No, I don't have that attitude to mains. I do really respect mains, but I do not fear it as so many other on this forum seems to do because I understand what can be dangerous, and what is not. I have formal education and work traing to say so, and I am allowed to work on this kind of equipment according to Norwegan law which actually has specific requirements for skills.Itisahugedifference between 250 volts and kilovolts. When people talk about electrocution because this stereo lacks grounding, they need to be told the truth, namely that 250 volt is a completely different beast than anything in the kilovolt-domain. There is a very good reason why the European low voltage directive ends at 1000V ac, and that a normal electrician is not allowed touch wiring above that.When people keep on talking about mains as something extremely dangerous regardless of the setting, they cause more harm than good to beginners. Any person above 8-10 years old, and living in a country with mains will know that mainscanbe dangerous. If we treat it with common sense it is safe.The fact that any properly designed and built USB charger with no more than 4mm clearance and 5mm creepage is perfectly safe according to both IEC and all European safety agencies should ring a lot of bells. But, unfortunately, people controlled by fear does not get it. They keep on with scaremongering that will hide the real danger electricity can cause.Many people seems to believe that low voltage is safe.The European regulations are based on that no current above 30mA shall pass through a person's heart, because 30mA will not cause severe harm to anormalperson. Based on statistics, they found that a normal person will have a skin resistance that will give no more than 30mA if exposed to 50V ac. This is not the same as anything below 50V ac is safe. This is the reason why some types of environment will require 24V or even 12V SELV equipment. When in a bath tube for instance, anything above 12V is considered dangerous.Even if you don't get a cardiac arrest by 30mA, a current below that can cause severe harm, given the rigt conditions.Some years ago, the most important cause for death among Norwegan electricians was not electrocution. It was the combination of a tall ladder, a light shock and an unfriendly meeting with the concrete floor...If you care that much about beginners googling around, you should not discuss anything related to mains. You will always find someone that will do silly things. If you find it difficult that I write something thatistrue, because somebody can misunderstand it, we are heading in a completely wrong direction. The only way we can interact safely with electricity, is when we act based on understanding.Maybe you should add a couple of lines to your signature telling beginners to stay away from mains until they have got enough understanding tho handle it in a safe way?

author: b_force
author_rank: Super Contributor
timestamp: July 29, 2017, 04:19:57 pm
content: Quote from: tronde on July 29, 2017, 04:02:53 pmThank you

author: Specmaster
author_rank: Super Contributor
timestamp: July 29, 2017, 04:38:04 pm
content: Personally I would go ahead and ground the chassis anyway and then worry about and hum loops later if and when any are produced. I suspect that its going to be unlikely as most audio I have seen normally only take one end of a screen cable to ground to minimise any risk of hum being induced. Its easier to fix hum loops then fix a person who has received a fatal shock thats for sure.. just ground it and be done with it. Unless its a real piece of hi-fi quality audio, any slight hum is unlikely to be heard anyway as 50hz is pretty low frequency and some of the so called audio gear would struggle to reproduce that level of sound anyway.

author: Gyro
author_rank: Super Contributor
timestamp: July 29, 2017, 05:03:12 pm
content: A couple of corrections guys...Quote from: b_force on July 29, 2017, 03:57:03 pmThere are several ways that the chassis can become live in Class II consumer gear, you mentioned two of them. There is also failure of fixings, inappropriate choice of board materials. Some may visibly evident, some may require vigorous shaking, some may have no outward signs. That's where defensive design, proper testing and certification come in. In addition I would always take a sample unit into the car park and drop it from head height a few times as a 'belt and braces' sure it will break but will it break safely. Slavishly clearance figures doesn't do it.Quote from: tronde on July 29, 2017, 04:02:53 pmThat's Body, not heart. It takes way less than 30mA directly through the heart to cause fibrillation. The 30mA figure, assuming limb to limb is designed to ensure prevent the heart, shunted by other body tissues, won't go into fibrilation.

author: tronde
author_rank: Frequent Contributor
timestamp: July 29, 2017, 05:04:03 pm
content: You don't need to fix any person.You really must stop these claims. They are WRONG. Please tell us why you must fix a person with this stereo, but not with a legal USB charger designed without any earth or several layers of insulation. Please tell us. You must obviously know someting neither the IEC nor any of the European safety agencies are aware of.The best you can hope for with the charger is 4mm clearance and 5mm creepage. It does not kill you. Why do you think it is different with this stereo? It was designed to be safe as it is, and it is still safe that way. If the stereo is marked as "double insulated" as it would have been in Europe, it is illegal to add any PE, regardless of your feeling for "safe" or "unsafe".

author: Zero999
author_rank: Super Contributor
timestamp: July 29, 2017, 05:11:11 pm
content: Quote from: Specmaster on July 29, 2017, 04:38:04 pmWhilst that probably wouldn't do any harm, I see little point in connecting the chassis to earth. Do it if it will make you feel better but if you're really worried about safety, there are other things you can do which are much more effective, such as:Adding a cable tie to secure the power cord.Covering the connection from the mains to the PCB with heat shrink or acid free silicone (don't use the stuff which emits acetic acid when curing, it can cause corrosion and make it worse)Putting some flame retardant insulating material, such as kapton tape on the case below the PCB.QuoteIt isn't 50Hz which causes most of the mains hum because, as you've correctly state, 50Hz isn't very audible, but the harmonics which can be quite loud.

author: tronde
author_rank: Frequent Contributor
timestamp: July 29, 2017, 05:11:29 pm
content: Quote from: Gyro on July 29, 2017, 05:03:12 pmDoes this change the reason for the choice of 50V? No?Does it make voltages below 50V safe? No?

author: Specmaster
author_rank: Super Contributor
timestamp: July 29, 2017, 05:58:56 pm
content: Quote from: tronde on July 29, 2017, 05:11:29 pmYou're right, it depends on where the shock is received and also on the person state of health as well as the actual conditions in how the shock was received, could be standing in deep flood water and unplugging the equipment. A shock in conditions like that could well be fatal. I believe I'm right, but not positive about this but I think a current of less than 10ma flowing across the heart is enough.

author: Gyro
author_rank: Super Contributor
timestamp: July 29, 2017, 06:19:55 pm
content: Quote from: tronde on July 29, 2017, 05:04:03 pmI don't know where you've dragged the USB charger up from, we were talking about metal cased class II consumer equipment. Metal cased Class II is a lot more difficult to get right than a USB charger.I think one of the reasons that we're talking as cross purposes is that I'm talking from the equipment designer's perspective. I've already said that the OP's unit looks safe [EDIT:from what I can see within the limits of the photo!], after a basic check of the condition of the end of the mains lead.My point is that, when designing equipment of this type, there are so many other things to be taken into account than meeting a basic creepage and clearance spec. There are many external factors such as handling shocks, aging, the old incontinent old cat finding a warm place to sleep! There are so many thing to consider to produce a consistently safe product...- PCB material strenght and brittleness under shock - I've seen badly designed equipment where all four corners of the SMPS PCB have snapped off!- Lengths of wiring assemblies - not just the mains lead if it becomes disconnected, it's also the length of internal secondary side wiring looms - can they become disconnected and touch components on the primary side of the power supply?- Can fixings become loose?- .... It's a long listMaybe I am guilty of trying to insert some education into this thread. What I am saying is that creepage and clearance are thevery startof the design process, not an assurance that, if met, then everything will be fine on every unit. That's just not acceptable for a volume product. After all, a designer has to be able to sleep at night!Even when meeting all appropriate regulations I still have reservations about what they permit. For instance allowing ventilation holes to be slots. They will quite happlly pass the EU 3mm finger probe test but will still allow a small child to post metal paperclips into the enclosure and bridge the safety clearances. Such possibilitiess can be a worry in the early hours despite your best efforts.Just one other thing, it can't be illegal to ground a Class II product. Unless it has zero external interfaces, it must be able to tolerate any / all of their shields being grounded and through them, the case itself. Itisillegal to modify the case in any way however (To clarify, that includes fitting a ground lead connection under a fixing screw).

author: John B
author_rank: Frequent Contributor
timestamp: July 29, 2017, 10:31:18 pm
content: Well this was a bit of a hornet's nest. To clarify a few things:-Its a Sony HST V202R for anyone curious.- There is no insulation under the mains PCB, probably just a shadow from the camera flash. The posts that the mains wiring connect to go straight through the board and are exposed underneath the board.- The big transformer in the photo is bolted to the sheet metal base, the same thing that the mains PCB is bolted to.- The photo might be a bit confusing. I have to lay the unit on its side because the whole thing is actually quite flimsy.- This unit will probably operate as a floating system. It has an external vinyl record player which is powered through this unit, and also has passive speakers. The only potential grounding point is if its connected to a grounded CD player through the RCA jacks, or if the headphone jack is utilised. Then you have to rely on the piddly earth shield of an audio cable as the grounding cable.This thing is probably over 20 years old. That could mean many things depending on your perspective. It could mean that it's proven to be safe, or it could mean that the chances of something NOT going wrong are diminishing over time. I think of it like my car: its over 20 years old, but I have done lots of modernisation with areas such as the suspension and brakes. Old stuff can benefit from a modern perspective.As an aside, I am repairing cracked solder joints due to mechanical fatigue over time. So the flexible nature of the chassis is now manifesting itself in at least some mechanical failures.At the very least I will explain my concern to the person who owns the unit. They are a friend and so I can talk to them easily. Would you not point out your concern?

author: Specmaster
author_rank: Super Contributor
timestamp: July 30, 2017, 12:08:16 am
content: Looking at the spec for this, any hum loops will be heard seeing as freq response goes down down to 17Hz so they could be quite deep in their sound. If you have the speakers to hand, I'd be inclined personally to ground the chassis on a 3 core lead for safety sake and then test the unit and deal with any hum pick-up while you have the unit. It is far better to do that now then wait until such time as your friend adds a newer and grounded CD player for instance and then discovers hum loops and then you have to go through it again.It is also far safer especially as you pointed out, the headphone jack is connected to the chassis anyway and I'd personally rather have earth potential near my head than line potential for very obvious reasons.

author: floobydust
author_rank: Super Contributor
timestamp: July 30, 2017, 01:42:09 am
content: John B, as you can see there's a lot of speculation, emotion and opinion regarding safety on older gear.Why don't you do a hi-pot test, this is standard procedure on something like this. Unless we all want to speculate about the mains transformer construction tooI don't see the product being dangerous, as much as you are scaring the owner into throwing it in the garbage.It was designed with the method of protection as reinforced/double-insulated (floating) which is commonplace in AV equipment, power tools, hair dryers, fans, lamps etc.The mains PCB is not supposed to move around, it's not a portable product. Sony sheet metal is flimsier when the cover is off.I do not like the mains cord, SKX cable not used in North America yet. I think the tug test is tougher here.

author: Electro Detective
author_rank: Super Contributor
timestamp: July 30, 2017, 03:03:55 am
content: yep, a poor man's hi-pot test(if conducted properly without trashing DUT)using a basic insulation/megger/megohm tester at 250v and 500vsoon decides the 'safety' condition of the deviceWarning:"Don't try this at home"if not familiar with an insulation tester,you may zap components and get bitten by it !

author: Cubdriver
author_rank: Unknown
timestamp: July 30, 2017, 06:43:48 am
content: Quote from: John B on July 29, 2017, 10:31:18 pmOne question is where are the cracked solder joints you're repairing? Are they in the line side of the power supply circuit, or elsewhere? If in the AC section, I might be at least somewhat concerned, but that would depend on their location and nature. If somewhere other than the power supply, then I see much less of an issue.The fact that it's around 20 years old and is a consumer product likely built in the tens of thousands (along with additional tens of thousands of other, similar models of similar construction) leads me to believe that it's likely quite safe - if it were not, by now there would have been some sort of a ruckus raised about people being electrocuted by them, and lawsuits would have flown.If it makes you more comfortable, then put a piece of fish paper on the chassis under the board, and/or put a dollop of electronics grade RTV on the exposed pins, as others have suggested. If the cabinet flexes enough for the board clearance to be an issue, I suspect that it will be the result of having taken heavy physical damage, and at that point anyone foolish enough to plug it in almost deserves to get lit up - at some point one must exercise a tiny bit of common sense and be smart enough to realize that if the piece of gear looks like it was run over by a bulldozer that they should NOT plug it in and attempt to turn it on.I agree with what was posted earlier that people need to be less freaked out about AC mains. Please note that this is not a digital condition where "less freaked out" = "completely care free, let's down a fifth of Jack Daniel's finest Tennessee Whiskey and go work on the breaker panel". Think linear - by less freaked out, I mean not getting nervous because the device built by the thousands that has worked for 10 or 20 or 30 or more years doesn't meet today's safety specs. If, for instance, 6mm of clearance was the spec when it was built, and 6mm has been fine for 20 years, it's unlikely to begin arcing over tomorrow because the new spec now says 8mm. AC Mains must be respected, and worked on with care, but if due care is taken they are not terribly dangerous to work on. The key is to read up and learn about the dangers, and act accordingly.-Pat

author: Gyro
author_rank: Super Contributor
timestamp: July 30, 2017, 10:15:59 am
content: Quote from: John B on July 29, 2017, 10:31:18 pmAh, good. Back to practicalities.I have the same question as Pat - if the joints you're having to rework are on that power board(?) then you might want to add a bit of belt and braces sheet insulation, otherwise, I wouldn't bother. I've already mentioned checking the mains lead.Looking at the construction, you have bits screwed to the base and the rear panel - Sony were obviously aware of the issue of differential movement - you can see that by the length of the wire jumpers between the base PCB, the main transformer PCB and the transformer (creating a production nightmare for themselves in the process). As long as those aren't the joints that you're having to repair then I wouldn't be too concerned.There's no inherent reason why a 20 year old bit of kit would be any less safe than a modern one - it might actually be safer in some respects due to the nice chunky linear supply and Japanese design / components. SRBP boards don't age that well, track adhesion isn't that great and they become more brittlewith age but there are no obvious cracks (the main board might be a different story of course).Probably the best advice I can give is complete your repairs as quickly as possible and get the lid screwed back on. Those cabinets rely heavily on the lid to provide rigidity. The longer you have the lid off, the more joint failures you're likely to have to fix.Chris

author: Specmaster
author_rank: Super Contributor
timestamp: July 30, 2017, 05:00:30 pm
content: Quote from: floobydust on July 30, 2017, 01:42:09 amIsn't double insulated only applicable when the equipment is constructed out of a non-conducting material, such as fans, hair dryers power drills etc are, find an industrial fan for instance and they will be made out of metal and fitted with a 3 core cable, 3 pin plug so that the exposed metal can earthed or grounded so as to protect the user from a shock in event of problem occurring which allows the metal to become live. Yes it shouldn't do in a well designed product but there is always that chance. Granted, the current standards were not in force when it was made, but there was a reason why modern standards were introduced so if the old standard was perfectly safe, then why did the authorities feel the need to write new standards?

author: Vtile
author_rank: Super Contributor
timestamp: July 30, 2017, 05:04:44 pm
content: There is always the insurance, politics and lawyer lobbying fear factors.

author: Gyro
author_rank: Super Contributor
timestamp: July 30, 2017, 06:00:39 pm
content: Quote from: Specmaster on July 30, 2017, 05:00:30 pmNope, it's fully applicable to (appropriately designed of course) metal cased equipment too. Specifically, in the case of consumer A/V equipment the requirements are covered under EN60065 (it also covers things like fire risk). The latest version is EN60065:2014. Before that 2011 and, I think 2002.Note that things like USB chargers get an easier ride by coming under the IT equipment safety standard EN60950. Jammy gits.It's the nature of standards to evolve with time, otherwise what would the standards committees have to lunch on. <cynical emoticon missing>. Real life experience and changes in technology (eg widespread SMPSs) do result improved standards, that remain relevant over time, however.P.S. Those are the European specs, there are equivalent specs for other parts of the world. The British Standards spec was harmonized into the European spec as BS-EN60065.

author: tronde
author_rank: Frequent Contributor
timestamp: July 30, 2017, 06:49:30 pm
content: Quote from: Gyro on July 29, 2017, 06:19:55 pmThe reason is becuase most people can relate to them.When they are considered as safe with 4mm clearance and 5mm creepage it does not make any sense to talk about electrocution because the stereo is in an ungrounded metal case.It does not matter whether the enclosure is plastic as in the charger or metal as in the stereo. The imortant thing is if the product has any "exposed parts" that can come in contact with live voltage. The size of the exposed part does not matter. The charger will usually be in a plastic enclosure, but the USB contact and the 5V out is "exposed", and it is only separated from the danger by 4 and 5mm.People tend to misunderstand the term "double insulated". It does not necessarily mean "two layers of wrapping". It does mean that the insulation shall provide the same level of protection as two layers. In the standards they list clearance and creepage distances. Those listed as "reinforced" is meant to give the same level of safety as two layers of insulation material.You are of course correct when you say that we should opt for more than the bare minimum when we design something. You suggest 8mm. That is in fact the creepage distance normally used in medical equipment, so it will give a very high level of insulation.You are also right about mechanical stress. They test for mechanical stability if you do a certification test, so it is obviously important.My intention with the first post was, and is, that people must get a realistic view on electrical safety and danger.250V is the normal upper limit for domestic mains. It is of course dangerous if you touch bare wires, but it is not like higher voltages that will easily flash over several milimeters as many seems to believe the mains will do too.You say in a later post that the USB charger is subject to a lighter standard. Not necessarily. You can choose to certify and test some types of"multi media equipment" to the same standard.The intended use and environment plays a big role in the design and certification process. Equipment meant to be used in a normal office / living room environment is subject to lighter regulations than something meant for use in the kitchen or outdoors or as toys for instance.Edit: Some of the typos.

author: Specmaster
author_rank: Super Contributor
timestamp: July 30, 2017, 07:38:59 pm
content: Quote from: Gyro on July 30, 2017, 06:00:39 pmOh, so are you telling me then that when I buy up old test equipment like signal generators, Heathkit Valve Voltmeters and the like that were originally wired up with 2 core cable and I rewire them with 3 core and 13A plug suitably fused that I shouldn't do that but leave them as they were?

author: ebastler
author_rank: Super Contributor
timestamp: July 30, 2017, 07:57:21 pm
content: Quote from: Specmaster on July 30, 2017, 07:38:59 pmNo, actually Gyro was telling you that "double insulated" is a category that is also applicable to devices with metal enclosures. He corrected your false conjecture, and gave specific references.How about acknowledging that you were mistaken, and thanking Gyro for the correction? Why do you need to react with an exaggeration and (presumably intentional) misinterpretation of his further comments?

author: Gyro
author_rank: Super Contributor
timestamp: July 30, 2017, 07:58:45 pm
content: Quote from: Specmaster on July 30, 2017, 07:38:59 pmI'm not telling you anything of the sort.I'm telling you what the current standards are for Consumer A/V equipment, the question you seemed to be asking. The OPs A/V equipment was built to a Class II double insulated standard.None of the stuff you just mentioned is anything of the sort. Don't blame me if you've bought a bunch of old test equipment that needs making safe!P.S. Thank you ebastler.

author: Gyro
author_rank: Super Contributor
timestamp: July 30, 2017, 08:00:20 pm
content: Quote from: tronde on July 30, 2017, 06:49:30 pmI'm sorry tronde, we wasted a lot of OT time on this yesterday, I really don't want to get into it again but I'll try to summarise some points.The reason I called you on USB chargers is because they are covered by a completely different safety standard to consumer A/V equipment that the OP was talking about - In Europe, EN60950 versus EN60065 as I indicated in my last post. It doesn't matter if people can relate to them or not, different equipment type, different safety standard.I didn't want to further complicate things yesterday but you keep quoting your 4mm clearance 5mm creepage and all will be well with the world. You've clearly not designed high volume consumer (I have). You need to understand that different safety standards have different requirements, for instance the magic figure of 8mm rears it's head in EN60065 (in fact Ithinkthe 2014 edition increased the standoff requirement for a primary voltage PCB from 8mm above the chassis to 10mm without an intervening insulating layer, ie. air insulation only. I can't say for sure, I don't have a copy, it's thankfully after my time). The standards also clearly define what is meant by reinforced, double layer etc. in the context of that equipment type (yes there is overlap between standards.Different safety standards take into consideration different usage and environmental conditions - for instance buildup of household dust, risk of foreign object introduction, the previously mentioned incontinent cat pee (happens a lot more often than you might think). The EN60950 IT equipment spec is quite lenient in comparison - it was born out of nice clean filtered computer rooms. It has since been stretched like a piece of elastic to cover Home PCs cheap, nasty, USB chargers (assuming that they have been manufactured to standard in the first place) - It has even been stretched to cover portable music players for heavens sake!I am just waiting for the day when some manufacturer manages to get his Smart TV certified as IT equipment rather than Consumer A/V, nothing would surprise me these days. Just to give a taste of recent EN60950 changes...http://ewh.ieee.org/r6/ocs/pses/EN60950.pdfI can't find an equivalent off hand for EN60065.If you want to see and compare the various standards then you have to buy them. They're not cheap either as they're intended for manufacturers...https://shop.bsigroup.com/ProductDetail/?pid=000000000030254244I fully understand that you want to take the 'fear' out of electrical safety, and I agree with you. You, in turn, must understand that every clause in every safety standard is there for a good reason, it's not open to discussion. It must be complied with, regardless of any 'percieved' risk. If a death happens, then it is the design authority for the equipment who is responsible, he can't argue that 'mains isn't really as dangerous as people think'.I really hope that this clarifies.

author: Zero999
author_rank: Super Contributor
timestamp: July 30, 2017, 08:14:45 pm
content: Quote from: Specmaster on July 30, 2017, 07:38:59 pmAs far as modifying old equipment is concerned. I'd go on a case by case basis. In some cases using three core cable would make it more dangerous and wouldn't consider that, unless it's necessary.

author: Specmaster
author_rank: Super Contributor
timestamp: July 30, 2017, 08:17:11 pm
content: Quote from: ebastler on July 30, 2017, 07:57:21 pmNo, I was not misinterpreting his comments intentionally at all, merely asking the question because from where I'm sitting, I could not see any difference between test gear in metal cases that was unearthed and audio gear in metal cases that was also unearthed. In both cases the user has to interact with the equipment and while everything is working as intended, no problems. The moment a problem does occur then the user could potentially be touching the full line voltage which here in the UK is 240v

author: Gyro
author_rank: Super Contributor
timestamp: July 30, 2017, 08:27:27 pm
content: The difference is that metal cased Class II consumer equipment is designed to entirely different and much stricter standards in terms of primary to secondary insulation, pcb clearances, safety critical component specifications, clearances from chassis metalwork etc. compared to the stuff you mentioned.

author: Specmaster
author_rank: Super Contributor
timestamp: July 30, 2017, 08:33:37 pm
content: Quote from: Gyro on July 30, 2017, 07:58:45 pmI'm really struggling to see the difference here, just how would anyone be able to differentiate between an item then like "old test gear" that needs making safe and "A/V gear built to class II double insulated standard". Does it carry some sort of sticker that states it conforms, modern stuff has the square in a square symbol to indicate that it is double insulated. In fact in the early days I often came across early valve radios and indeed TV chassis which were directly connected to the live supply, especially American equipment which had 2 pin plugs which could be plugged in either way round. In fact there are YouTube channels featuring repair shops where they come across this even today, 12voltvids is a typical channel that I watch and this cropped up lots of times on it.

author: ebastler
author_rank: Super Contributor
timestamp: July 30, 2017, 08:37:43 pm
content: Quote from: Specmaster on July 30, 2017, 08:17:11 pmAs already stated by Gyro, the difference is that the modern Class II equipmentis double insulated. That means that, if the outer enclosure is metal, there actually isredundantinsulation of all mains-carrying parts inside. This can take various shapes and forms -- extra large clearances, two layers of insulation around cables, etc..Another way to put it, "a problem" (as in "a single problem") doesnotcause any danger in properly designed Class II equipment. The double insulation is one incarnation of the "single fault tolerance" paradigm, which is a guiding principle in many safety standards.

author: Zero999
author_rank: Super Contributor
timestamp: July 30, 2017, 08:39:43 pm
content: There's also a big difference between audio/video and test equipment. They're used for different applications. Test equipment will be designed to more stringent standards than audio equipment.

author: floobydust
author_rank: Super Contributor
timestamp: July 30, 2017, 08:43:13 pm
content: How many decades is "old"?For this Sony, the safety standards changed little since the 1990's. Aside from protective insulation aging and cracking, the construction is not entirely unsafe.Silicon Chip Magazine antique tube radio restorations: add a fuse and proper strain relief, ground the chassis, new mains cord. Antique equipment had weak or non-existent safety standards. Makes sense to bring it up to something that won't kill or burn the house down, like a lot of antique gear could do.

author: ebastler
author_rank: Super Contributor
timestamp: July 30, 2017, 08:50:39 pm
content: Quote from: Hero999 on July 30, 2017, 08:39:43 pmRight. But the rationale is not that the life of a test engineer deserves more protection than the life of a consumer using an audio amplifier.Rather, for test equipment one can construe additional "single fault scenarios" that the user needs to be protected against.For example, the mains power supply is not the only source of potentially dangerous voltages in a piece of test equipment. If you measure a high voltage with your bench DMM or oscilloscope, a faulty test lead or coax cable (which is not double insulated) or a user error may cause that voltage to reach your test equipment's GND connectors (and its metal enclosure if applicable). Hence, these need to be connected to protective earth for safety! Just protecting them from the test equipment's built-in power supply via double insulation is not enough to keep you safe.

author: Gyro
author_rank: Super Contributor
timestamp: July 30, 2017, 09:06:29 pm
content: Quote from: Specmaster on July 30, 2017, 08:33:37 pmTo answer the easy question first, yes, double insulated items are marked with the 'Square within a Square' symbol - not a sticker, it's a requirement that it is permanently marked, silk screen or whatever.Early TVs were indeed often live chassis. If you think back though, their knobs and controls were plastic - even the ones with metal trim had plastic inners / shafts. Their aerial sockets weren't directly connected to the chassis - they included series RF capacitors in both the centre and shield paths (trust me). SCART and Headphone connectors didn't come in until after grounded chassis. Where TVs were the 'modern' pushthrough style (rather that recessed behind glass), the Implosion/fixing band around the screen was connected to chassis via a high voltage (~20Meg) resistor with parallel small value ceramic capacitor. That was just in case someone slipped something down the side. Those old TVs could be loosely regarded as 'reinforced' insulation in modern language, not bad, even if the back was fibreboard with coin slot fasteners. Cabinets were of course wood / plastic, not metal.Test gear is a whole bag of worms, I remember a Japanese signal generator I had with a 2 core cable, metal case and definitely wasn't safe internally. A lot of cheap US origin too with dodgy looking transformer insulation (manufacturers more used to working with 110V?). It's difficult to lump them together. As ebastler said, treat each one as an individual case and act accordingly.Quote from: Hero999 on July 30, 2017, 08:39:43 pmI think I have to disagree with you in safety terms. Consumer AV is manufactured to go in a domestic environment (kids) and in such high volumes that in safety terms there is no room for compromise. Test equipment components and operation will be obviously be, well, test equipment quality, there's no reason to argue that it is built to more stringent standards with regard to safety.

author: Gyro
author_rank: Super Contributor
timestamp: July 30, 2017, 09:17:51 pm
content: So much for a quiet night watching/ listening (via the RCA connectors on my double insulated TV and my grounded chassis valve amp and Tannoys!) to the Proms!P.S.Quote from: floobydust on July 30, 2017, 08:43:13 pmYoung enough.Agreed, particularly for a linear power supply model like that. No Y-cap spec changes to worry about etc. An insurance company might actually argue that modifying it by adding extra insulation is an unauthorized change from its approved state and has potentially changed its flamability characteristics. But then, insurance companies will argue anything if it avoids paying out.

author: Specmaster
author_rank: Super Contributor
timestamp: July 30, 2017, 09:37:36 pm
content: Thank you for providing some illumination on the subject, it is a bit clearer now

author: Specmaster
author_rank: Super Contributor
timestamp: July 30, 2017, 09:43:33 pm
content: Quote from: ebastler on July 30, 2017, 08:50:39 pmThank you some enlightenment but what about in the instance where either the DUT or the test equipment is connected via an isolation transformer? Also in an example of say using an oscilloscope to probe about in a DUT, where should the isolation transformer be, on the scope or the DUT?

author: ebastler
author_rank: Super Contributor
timestamp: July 30, 2017, 10:02:19 pm
content: Quote from: Specmaster on July 30, 2017, 09:43:33 pmIn my understanding, the scope should always remain connected to PE. (So you can be sure that its metal parts are safe to touch.) Connect the DUT via an isolation transformer if you want extra protection while probing it; especially if it is one of those "chassis at high potential" contraptions.

author: tronde
author_rank: Frequent Contributor
timestamp: July 30, 2017, 10:26:08 pm
content: Quote from: Gyro on July 30, 2017, 08:00:20 pmWell, some multimedia equipment is allowed to be tested to 60950, so not so wrong as you indicate.The origin of the discussion was the claim of being killed. I said, no killing here, and I used the charger as an example because it clearly shows that even small distances are safe in a domestic environment. Else it would have been illegal to sell and use.The 4 and 5mm is more relevant to the discussion than "being electrocuted" because it shows clearly that you will not be killed by those distances in a domestic setting. This applies regardless of the product being a charger, a TV or a stereo. I have also always made clear that the environment is part of the danger. As I wrote in my previous post, the expected environment plays a big part. That is why some multimedia equipment is allowed to be tested to 60950, and some not. The danger does notnecessarilychange by type of product, but more often by how the product is used and in which environment.It was you that complicated everything by talking about how a product could be improved by changing the design to allow for problem-free manufacturing of thousands of units. This is nice for the manufacturer, but it does not does not matter in this spesific discussion about what can be considered safe or not, so blame yourself on that.No, I have not designed high-volume consumer stuff, but I have done a lot of layouts for high-volume light-equipment. All tested and certified by NEMKO without problem, so I am not that far-out, I think.No need to elaborate more. I guess we agree one the most important; that the stereo in question does not appear to be unsafe by design as claimed by some.

author: Specmaster
author_rank: Super Contributor
timestamp: July 30, 2017, 10:46:14 pm
content: Quote from: ebastler on July 30, 2017, 10:02:19 pmWell I like to obtain old scopes and try and rescue them becoming landfill so you would always have the scope being used as the test instrument connected to PE and isolation on the other under test, OK.

author: tronde
author_rank: Frequent Contributor
timestamp: July 31, 2017, 01:22:29 am
content: This thread has diverted into two different problems.A:Guy finds old equipent and wonder whether it is safe or not.1:Open enclosure, and find out if it looks mechanically sound and without any obvious signs of electrical faults.2:If sound, measure actual clearance and creepage from anything mains to exposed parts. If clearance > 4mm and creepage > 5mmandintended use is normal office or living room environment you will most likely have no reason to wet your pants.B:This is what Gyro mixed in to the discussion.Guy gets a great idea for a product that will sell in huge numbers.1:Shell out a lot of money to IEC for all relevant standards.2:Spend a lot of time trying to figure out what is important.3:Implement what you think is important as best you can.4:Shell out a lot of money for a certification test.5:Repeat #3 and #4 and maybe #1 and #2 because you forgot something.OR as we didFind out what to sell1:Make an agreement with for instance NEMKO and pay something upfront.2:Tell them what you intend to make.3:Let them tell you what they would like to see.4:Implement what they asked for.5:Shell out a lot of money for a certification test.6:Be happy. If you didn't fail on EMC then, but that is a different case.

author: Electro Detective
author_rank: Super Contributor
timestamp: July 31, 2017, 04:41:28 am
content: LOL, you'd have to be rich or bonkers to stuff about modifying a formerly approved two core mains device to a 3 core question mark,with the possibility of anUNRELATED to the modmishap,beingsued to oblivionby some arrogant opportunistic pr!ck (no shortage of those todaythat must believe a well deserved visit to hospital on life support payback isn't going to happen sometime in the future)and being allowed back on the street with only your jocks left,classed as an un-seizable assetLeave the gadget as is, it worked then, it works now, move on

author: Vtile
author_rank: Super Contributor
timestamp: July 31, 2017, 08:01:25 am
content: Quote from: Gyro on July 30, 2017, 09:06:29 pmIf I add a bit more air around the scenery..One must remember that the distribution wiring scheme is also changed and so is building materials and techniques to some extend. Lets take the log cabin with wooden floor as a example. It does have one building material and it is a wood, which is a rather good insulator while its moisture content is typical what we typically call dry. As it is a log cabin it doesn't have running water or other metal stuctures. It does have one mains socket (110 or 240 V). Now the only socket is used to power the only electronic device in the cabin, which were old tuberadio with only 2 lead power cord. The chassis is all shiny bare metal (for sake of the story) and the other line of the cord is attached directly to the metal chassis. At the morning while mr.Mears were dry cleaning his living room with brucetwigs he removed the socket and didn't notice that he put it back at wrong way around. Now the chassis became to mains potential (voltage) and poor mr.Mears is toasted, isn't he?? Nope, because the archaic environment didn't have any path for the fault current to form. The wooden floor were insulator and all the other surfaces in the cabin except the radio chassis. So the user were still insulated (from ground at this case) and were like a bird sitting on the power line.Since then the environment have drastically changed, with electronics top of each other and more conductive surfaces in houses (water pipes and so forth). This leads to environment that more often than not is always dangerous for the user if the person touch a mains potential.This applies in some extend to test gear also. The routine to use of them might have been dramatically different than todays rather liberal "poke around culture" and so were often the environment where it were used.Edit. some typos and idiomics.

author: Gyro
author_rank: Super Contributor
timestamp: July 31, 2017, 09:14:37 am
content: @Vtile:QuoteYou have taken this thread way OT (again!) with your fanciful conjectures of why exposure to mains voltage isn't dangerous (is that 'at all' by now?). I'm not sure at this point whether you are deliberately trolling, or just have difficulty with estabished facts.The OP was asking specific questions about an item of Class II Consumer A/V equipment. I have gone to some length providing relevant details, spec references etc. and have provided my own (for what it's worth) clear opinion on the specific item.I don't care if Log cabins swept with spruce twigs, or any other domestic environment are envolved. Equipment is designed to strict an binding safety specifications where they have no latitude for fanciful stories.EDIT: The following quote from tronde, not Vtile (My apologies to Vtile):QuoteNobody (I certainly wouldn't, and I've designed several high volume consumer Class II A/V products) would get an idea for such a Class II product and go ahead and develop it without purchasing the relevant safety spec - which is actually very cheap in comparison with other costs for "a product that will sell in huge numbers". Yes, of course he would need to spend considerable time designing to meet the full requirenments of that safety spec. Yes, of course you take advice if something is unclear to you, either from an internal specialist or an external authority. Run several prototypes to finalise the design this is needed regardless for a product of any complexity. Submit a 'golden sample' to an acredited test house, together with full supporting documentation, which includes things like copies of safety body approval certificates from the manufacturers of all safety critical components. Then, be prepared the cost of rework and re-test of any issues of non compliance that the test house identifies. Without all of those steps it would be completely unsafe - and illegal to take a Class II product to market.... All of this is what real manufactuctures of Metal cased Class II eqiupment do, every day. It's not 'Amateurs night at the Circus'If you want to develop products by shortcut means, then put them in safety grounded enclosures or use an already approved external power brick.You go ahead and add as much "air" to the thread as you want. As far as I am concerned this thread has run its useful course and I'm not wasting any more time on it. I hope the OP has gained the information he needs and maybe others may have gained some value from it.Finallystopquoting your 4mm and 5mm mantra as the only safety metric, that advice isdangerousfor other people! I am sure that NEMKO would take a very dim view of you doing it on a public forum! It may be applicable to something that you have done, but the only figures that are relevant are the ones stated in the safety standards for that specific product category. It certainly isn't applicable to Metal cased Class II consumer!I'm not going provide you care and feeding any more. I'm out of here.

author: Vtile
author_rank: Super Contributor
timestamp: July 31, 2017, 09:42:15 am
content: Quote from: Gyro on July 31, 2017, 09:14:37 amNo, the OT were already antique radios and antique test equipments. Yes the exposure to mains voltage is relative as the voltage is a potential difference of two points. If you have only one point of contact there is no potential difference (except through non-galvanic paths) and no current flow and no energy to do the harm. Indeed I look this through electrical(power) engineering glasses not electronicsengineering glasses.PS. The 'fanciful story' and the next chapter after it hopefully gives some more understanding for random reader what is happening with the mains. It is not directed to you or not written as any sort of design instruction.

author: ebastler
author_rank: Super Contributor
timestamp: July 31, 2017, 10:53:39 am
content: Quote from: Vtile on July 31, 2017, 09:42:15 amUmm, no?!Look, the original post is still here for your convenience:https://www.eevblog.com/forum/beginners/grounding-old-equipment/And is is worded pretty clearly, and talks about one specific piece of stereo gear (only).

author: hermit
author_rank: Frequent Contributor
timestamp: July 31, 2017, 11:02:31 am
content: I had a customer that said every time she closed the refrigerator door it blew her house fuse. Cause? Her "electrician" had decided since neutral and ground were the same he would ground the socket by tying them together. Problem? He tied ground and hot. There most not have been a good earth ground in this place because it didn't blow the fuse until she shut the door and it contacted the register duct. This thing was right next to the sink where she did dishes. Can you imagine if she decided to reach over and get a cold drink?Again, you add something that wasn't there and you become a potential target. Yes the fault would REALLY be with the socket. You want to go to court and prove that? You charge enough for that repair to cover the legal costs if they arise? Some of my old stereo equipment came with a ground screw on the back. Of course back them most house receptacles were 2 wire. I lived in one place where they ran wire up through the old gas light pipe. But I digress. But then again, so has this thread.

author: Vtile
author_rank: Super Contributor
timestamp: July 31, 2017, 11:27:51 am
content: Quote from: ebastler on July 31, 2017, 10:53:39 amWell, I were indeed wrong about post #81 it is drifted to antique TVs and antique test instruments. Not antique radios and test gear. Good catch. Anything else?It is good that Gyro and some others have bring the specific information what current standards have to say on the subject, since those aren't accessible to general public due the huge $$$ of cost related to get a representive set of publications (while given some of the properties of the law) and the ever increasing update cycle (ripping off).

author: ebastler
author_rank: Super Contributor
timestamp: July 31, 2017, 11:51:01 am
content: Quote from: Vtile on July 31, 2017, 11:27:51 amI think there is a difference between (a) repeatedly trying to reel the thread back in, by pointing out why references to old test equipment etc. arenot relevantto the OP's question, due to differences in the safety requirements and standards, and (b) telling anecdotes about log cabins.Now excuse me while I look for the icon depicting "beating a pop-corn eating smart-alec"...

author: Vtile
author_rank: Super Contributor
timestamp: July 31, 2017, 12:01:04 pm
content: It definedly is not my fault if it is too much to ask to understand the anecdote, which by the way is pretty close to the typical imaginary excercises (like the story hermit shared) used in introduction level electrician training by many teachers.

author: tronde
author_rank: Frequent Contributor
timestamp: July 31, 2017, 04:35:01 pm
content: Quote from: Gyro on July 31, 2017, 09:14:37 amGyro, you must learn to READ.I have never claimed 4 and 5mm as theonlysafety metric. I have always mentioned that the environment must be considered.Already in my first post I wrote:"This is a stereo. It's meant for anormal domestic environment, i.e. no excessive humidity or dust. It is not ment to be mechanically abused as power tools are."I have also written:"The intended use and environment plays a big role in the design and certification process. Equipment meant to be used in a normal office / living room environment is subject to lighter regulations than something meant for use in the kitchen or outdoors or as toys for instance."But you prefer to be blind for this. Only you can tell why.Electrical safetyhas nothing to do with words written on a paper.Legal safetyhas something to do with words on paper.No product will become safe because of words, and no product will become unsafe because we call the product something else.What makes a product safe depends on the environment and physics. 4 and 5mmwillprovide the clearances necessary for normal mains voltages in anormaloffice or living room environment, regardless of what is written on any paper or what we prefer to call the product.The reason the standards increases this distances for certain products is not because we call the product someting else than computer or fax or monitor. The reason they demand more clearance for some products is because they know that those products probably will be exposed to a more demanding environment, for instance people acting stupid. They increase the safetymargin.Not necessarily because the product itself needs it, but because of the expected environment. They don't make a separate standard for every product imaginable. They try to group them according to expected use and environment.Your computer monitor with 4/5mm distances is considered perfectly safe when you use it as a monitor for your computer in your living room. This monitor will not become unsafe just because you hang it on the wall in the same living room and uses it as a TV together with a TV dongle. According to words written on paper, it is now a TV and should be tested as a TV to be conform with a more demanding standard. Because of this it islegally unsafe.It is stillelectrically safebecause it is still used in the environment it was designed for. If you move it to the kitchen or outdoors, you can find it to be both electricall and legally unsafe because the environment is too different from what it was designed for regardless of being used as a TV or a monitor.But - I don't think you ever will get it.It seems like it is impossible for you to see the difference between how to find out if anexisting productcan be considered as safe to use, and the design process needed to create a new product that will have to follow all legal requirement in today's legislation.

author: Zero999
author_rank: Super Contributor
timestamp: July 31, 2017, 05:28:12 pm
content: The standards are overkill in many respects, because they've been developed to cater for the worst case scenario and ageing. 4mm clearance and 5mm creepage are around an order of magnitude higher than what's necessary to insulate something at mains voltages. You could design a PCB with 0.5mm creapage between the mains and tracks exposed parts and it wouldn't shock anyone 99% of the time. It wouldn't pass the safety standards but it would still have more than adequate insulation for 230VAC.So why don't the standards just say 0.4mm clearance and 0.5mm creepage? Why 4mm and 5mm? Because the mains can have high voltage transients on it, which will easily arc across a 0.5mm gap and have enough energy to hurt someone. Even if the transient itself isn't enough to kill, the conductive plasma will connect the metal case to the live parts, causing mains current to flow to the user. To address this the standards take into account the expected peak voltage of the transients, how often they occur and the potential for injury when the insulation is breached. This is why the minimum distances are greater for an industrial, than a domestic environment and are greater reinforced insulation than single insulation, which is greater than functional insulation and that's dependant on whether it's before or after a fuse/circuit breaker.

author: Specmaster
author_rank: Super Contributor
timestamp: July 31, 2017, 05:39:32 pm
content: Quote from: hermit on July 31, 2017, 11:02:31 amWas this fridge wired up on a 2 pin plug by any chance? If so then it just highlights the issues I mentioned before and the fitting of a 3 pin plug and the introduction of an earth connection to the external metal work should really be belt and braces and not introduce any additional risk or problems surely?

author: floobydust
author_rank: Super Contributor
timestamp: July 31, 2017, 05:51:54 pm
content: Appliances, like refrigerators are PE grounded, 3-pin plug as you call it.It's cheaper than double-insulation for the compressor motor, defrost heater etc.

author: Gyro
author_rank: Super Contributor
timestamp: July 31, 2017, 06:00:23 pm
content: Quote from: tronde on July 31, 2017, 04:35:01 pmSigh, ok you've provoked me into final comments1. I could go on at length about degree of contamination - often old consumer equipment isverydusty inside, in a smoker's homeMUCHworse.2. As Hero999 states, the mains supply is subject to transients. Scores of pages are spent in the Test equipment section on the safety of DMMs which might very occasionally be connected to the mains by unwise people. Most of those have creepage and clearances greater than 4/5mm but they lack the additional surge withstanding components to withstand possible transients. AV equipment is normally permanently plugged into the mains.I could go on but since you have chosen to differentiate your definition of electrical safety from the Legal definition of safety.... and since this is theBEGINNERSsection of the forum...Which definition of safety will an Insurance Company or Court base it's judgement on in case of death or injury through Electrocution or Fire? The LEGAL definition of safety or the trondeTMdefinition of safety?

author: Specmaster
author_rank: Super Contributor
timestamp: July 31, 2017, 06:14:29 pm
content: Quote from: floobydust on July 31, 2017, 05:51:54 pmThey should be I agree, but the post by hermit sort of suggested that maybe the 3 pin plug had been removed and a 2 pin one fitted in order to fit an existing 2 pin socket otherwise why would the "electrician" feel the need to tie earth and neutral together? As he said there was a very bad earth (ground connection in the house anyway) and it was only when the fridge actually touched a duct. So if it was a 2 pin plug, incorrectly inserted in the socket then it would not blow the fuse until the live metal of the fridge physically came into contact with a good ground such as the duct?

author: hermit
author_rank: Frequent Contributor
timestamp: July 31, 2017, 06:39:03 pm
content: Quote from: Specmaster on July 31, 2017, 05:39:32 pmThe fridge was new so it was three pronged. It was an old house so there were only 2 wires to the receptacle. That's why the "electrician" got the bright idea to run a wire between the ground and neutral on the new socket. In theory I guess that is better than leaving the ground disconnected.Quick edit to clarify something in a post after the one I'm answering. The house was old so it was a 2 wire system. I have no idea how the heating register ended up being ground.Off topic, but hey does that matter at this point, I had one instance where someone ran 240V to their garage and terminated it with a 120V outlet. Then they sold the house and the new owner had no idea. I was trying to figure out how they blew every motor in the machine. As I was getting back into the truck it struck me the light bulb seemed awfully bright. I got back out and went back to measure the voltage. Consumers can be so much fun. In this case it was the repair technician put at risk by the customer.

author: Specmaster
author_rank: Super Contributor
timestamp: July 31, 2017, 07:06:33 pm
content: Quote from: hermit on July 31, 2017, 06:39:03 pmOh OK that answers that question nicely then it was one of those "Electricians" who can't tell live from neutral.

author: Gyro
author_rank: Super Contributor
timestamp: July 31, 2017, 07:11:26 pm
content: Quote from: Vtile on July 31, 2017, 12:01:04 pm@Vtile,I'm sorry. I have realised that I accidentally attributed some of tronde's comments to you in my post earlier today. I have gone back and added a clarification. Please accept my sincere apologies, I should have been more careful - and more gentle towards you as a result.Chris

author: floobydust
author_rank: Super Contributor
timestamp: July 31, 2017, 08:04:18 pm
content: I have seen electricians connect an outlet's GND to NEUTRAL instead of leaving it floating, with old (1950's and earlier) houses in North America, that have 2-prong outlets.The reasoning for this - cutting off the (fridge's) 3rd-pin (GND) it's more dangerous leaving it floating.Since NEUTRAL is bonded to earth-ground in the breaker panel, it ends up being a ground connection.This isn't my idea, it doesn't meet electrical codes. The alternative is to update the outlet by ripping up walls and stringing a GND wire, do it right.Too bad that electrician connected to HOT and didn't check.

author: Vtile
author_rank: Super Contributor
timestamp: July 31, 2017, 09:02:34 pm
content: Quote from: Gyro on July 31, 2017, 07:11:26 pmWell, like wisely said by Hero (pun intented) the subject usually ends up in some form of depate between - I suppose - people with different backgrounds.

author: Specmaster
author_rank: Super Contributor
timestamp: July 31, 2017, 10:46:01 pm
content: Quote from: Vtile on July 31, 2017, 09:02:34 pmI love it when a discussion takes multiple routes like this, its good to promote healthy debate and it can be very educational as well so wheres the harm. We are no different to other so called experts, some of whom cannot even agree on the correct way to make a cup of tea. There is always at least 2 sides to every storey and it is nice to see other peoples view on something and respect their views and experience, no man knows it all.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: July 31, 2017, 11:08:53 pm
content: pls Don't be rude to others in the thread, there is no need.I actually agree that there often is a difference between what is safe and what is legal. But for ease of effort and ease of mind I just normal go as close to the letter and spirit of the laws as possible.Sometimes it's not easy.In this case what is the law? And here's a clue, it's not an international standard. Though no doubt it will be close.I haven't seen anyone quote the relevant standard or even better post that section up. What is legal in your countries may not be legal in whatever state of Australia the OP lives in.The relevant standards are probably found within these publications.AS/NZS 60335.1:2002 , AS/NZS 5762:2005, AS/NZS 5761:2011 , AS/NZS 3760:2010These all cost money (they should be free!) so for a small repair such as the OP was talking about it's isn't feasible to thoroughly research this.So then you have to fall back on having a guess at what is legal.IMO this equipment would fail test and tag as is(AS/NZS 3760:2010), but would pass if it had an extra layer of insulation of the 'live' parts.This is why I said it wasn't safe, and so for a customer or friend I would go the extra yard and put the insulation in.That said if you left it as is, it is still probably safer than crossing the road, which is perfectly legal.

author: Nusa
author_rank: Super Contributor
timestamp: July 31, 2017, 11:31:38 pm
content: Except all of those standards you quote are probably too new. If it's from the 1990's, it only has to meet the standards in force at the time of manufacture.

author: Specmaster
author_rank: Super Contributor
timestamp: July 31, 2017, 11:40:24 pm
content: Does not mean that it can't or shouldn't be upgraded to the newest standard or indeed improved if its not possible to reach the latest standard does it.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: July 31, 2017, 11:47:57 pm
content: Quote from: Nusa on July 31, 2017, 11:31:38 pmYeah good point, but these standards apply now, and in them they probably mention that if the equipment was made under an older standard then the equipment would still be ok if considered 'safe'.('Safe' is deliberately a loose term. ) At least that is what happens in one standard AS/NZ3000.But there is also an issue depending on the customer.If the customer is a business or organisation then it must be tested and tagged tocurrentstandards at regular intervals.IIRC in the OPs case it is a friend.So I guess for small jobs we are back to make it as safe and legal as is reasonably possible.

author: Nusa
author_rank: Super Contributor
timestamp: July 31, 2017, 11:52:06 pm
content: Quote from: Specmaster on July 31, 2017, 11:40:24 pmUnless you are willing to take personal liability when you certify it safe without a certification process, upgrading it may legally be a very bad idea.

author: Specmaster
author_rank: Super Contributor
timestamp: August 01, 2017, 12:24:36 am
content: Quote from: Nusa on July 31, 2017, 11:52:06 pmWell in the UK all extraneous metal should be grounded then under those conditions, if the metalwork is accessible by the user without the need for any tools being used then yes, my interpretation is that it ought to be grounded. If it is not touchable under the normal operation then no, leave it.

author: Zero999
author_rank: Super Contributor
timestamp: August 01, 2017, 08:01:59 am
content: Quote from: Specmaster on August 01, 2017, 12:24:36 amNow you're confusing metal cased class 2 equipment, with the fixed electrical installation.

author: Specmaster
author_rank: Super Contributor
timestamp: August 01, 2017, 08:35:04 am
content: Quote from: Hero999 on August 01, 2017, 08:01:59 amIf the metal case is nothing more then that, a case that surrounds the equipment to keep people from coming into contact with live parts and also forms a cosmetic function, then whats the harm in grounding it?A cable going to it or another A/V unit or similar could be in contact with the casing and have compromised sheathing, an exposed live conductor could come into contact with the metal work and adjacent to the unit could also be for arguments sake, metal gas fire which must be earthed if the user was to be touching the gas fire and the A/V unit a shock would be the end result???

author: Gyro
author_rank: Super Contributor
timestamp: August 01, 2017, 08:59:09 am
content: Quote from: Nusa on July 31, 2017, 11:31:38 pmLuckily for the OP, EN60065 was already in place in the 1990s so his Sony equipment (as a responsible manufacturer) would clearly have been adhered to. The creepage and Clearances will already be well in excess of the figures tronde keeps quoting. Some liberties have been taken with the mains cable termination, either as a slightly dodgy cost reduction or possibly (given that the wires are soldered to a plug header!) somebody has already been in there and replaced (lengthened?) the mains lead. The original crimped cable socket would have been practically impossible to remove - the inserts are very well fitted in the housing (for obvious reasons) and there are no exposed metal tabs (also for obvious reasons).Quote from: Nusa on July 31, 2017, 11:52:06 pmThat my friend isTHE VERY CORE OF THE ISSUE, It is the reason for myRedwarning to tronde - It is alegalissue.If you modify the equipment in any way (you can probably justify repairing dry joints or replacing non safety critical components - as long as you re-assemble it in exactly the same way), then you take over the legal responsibilty for its safety.Companies carry significant public liability insurance - that is not to say that the Design authority and Directors are immune from individual legal liability. If you are repairing stuff for friends then you won't have this insurance. You may be the best of friends, but their home insurance company will most certainly not be your friend if the worst happens.This is the reason that I restrict the favours I do for friends an neighbors these days to 'taking a look' ("no, sorry, that's not safely repairable") and basic non-critical repairs. I know this specific standard but it's still not worth the risk.Your point about modification is very well made.In legal terms, you are not competent to make judgements on modifications. As I mentioned in a previous post, even adding additional insulating material, blobbing silicone etc. is changing the flamability characteristics of the product. It could come back to bite you.My advice to the OP (I think I'm repeating myself here), leave the product exactly as it is. If there was a safety issue in modern terms,then Sony would have recalled it. If you are confident in your abilities, restrict your repair the failed solder joints if they are in a non-safety area (not just the live section, but also anything related to fusible resistors protecting internal rails from overload too). Basically avoid anything with an 'exclamation mark inside a triangle' in the service manual. Otherwise you could compromise it's flamability characteristics. Then put everything back exactly as you found it. Most service manuals these days include insulation measurements to be carried out on completion of service.While I have some sympath with tronde's points about breakdown voltage and the laws of physics (which of course I agree with), the concept of [Edit: "legally unsafe"] but still "electrically safe" cannot be allowed to stand. The consequences of anything you do in opening and repairing the unit can only beLegal.I hope this clarifies the issue a little better.

author: Zero999
author_rank: Super Contributor
timestamp: August 01, 2017, 09:59:30 am
content: Quote from: Specmaster on August 01, 2017, 08:35:04 amThere's no harm in grounding it, just that it's unnecessary.QuoteThe gas fire should be earthed, if it's not a class 2 appliance but that's totally irrelevant. It's a different piece of equipment, creating a hazard. One could also argue that earthing a metal chassis can make it more dangerous in certain circumstances, because it will provide a return path for current from a neighbouring piece of equipment who's chassis has become live due to a fault. Touch the earthed chassis and live chassis, on the faulty equipment and receive a potentially fatal shock, if there's no RCD/GFCI to save you. Had the chassis not been earthed, the person would have less chance of a fatal shock, because the current would be much lower.The above is all irrelevant to the discussion because it involves a fault somewhere else, which is nothing to do with metal cased, class 2 audio equipment.

author: Specmaster
author_rank: Super Contributor
timestamp: August 01, 2017, 10:27:50 am
content: I think that where a lot of confusion comes from is the fact that this forum is of an international nature and what may be applicable in one country is not in another and then of course the various countries wiring regulations also disagree with each other in certain countries and these also muddy the waters to an extent.My point about grounding extraneous metalwork and connecting that metal case of the said Sony (agreed they are a responsible manufacturer) equipment stems from the same argument. In the case of a window it is perfectly feasible for someone to run a power cable via an open window to feed say a lawn mower. The cable could have a damaged sheath with a exposed live cable that could come into contact with an un grounded window frame even as a result of the window being closed onto and cutting into the cable, so someone could then touch at the same time the window frame and something else that was grounded and a possible fatal shock could be received as a result.Audio and visual gear such as hi-fi separates for example are designed to be stacked on top of each other, each having its own power cable and the way that some of these are connected together can be a right mess, I know from personal experience. It is also conceivable that one or more of these power cables could be routed between the units in some cases and if the cable was in a poor state with the outer sheath compromised and also an damaged secondary sheath on the live core, touching the metal case would mean that at least one piece the A/V equipment would have a case that was at supply potential.That in its own right, under most conditions is not as dangerous as it sounds until the operator also touches simultaneously say a grounded radiator, or as some else had mentioned, introduces for example a grounded CD player and they happen to be touching that at the same as adjusting volume on the compromised amplifier unit then they could once again receive a nasty shock as a result.My argument has never in the main been about a fault occurring internally within the equipment, more of an artificially imported one, often by way of something that the owner has done. Sometimes you have to protect the general public from their own actions as in the two incidences I have highlighted the end result should be that the circuit protective device should operate to protect the people in these circumstances.

author: hermit
author_rank: Frequent Contributor
timestamp: August 01, 2017, 05:45:17 pm
content: Quote from: Hero999 on August 01, 2017, 09:59:30 amAnd if the end consumer wishes to then there is probably an existing screw that can be backed out and used. A grounding screw was actually provided on some of this two pronged stuff.

author: Specmaster
author_rank: Super Contributor
timestamp: August 01, 2017, 06:21:45 pm
content: Quote from: hermit on August 01, 2017, 05:45:17 pmWell that was my understanding as well and in which case you're back at the same location as I was at earlier in this thread with effectively replacing the 2 core with a 3 core cable and grounding the case. I suppose the difference is that by using the external screw your not modifying the manufacturer's internal connections or their means of entry? Where I have done this myself, I have always replaced the makers cable grommet/gland/clamp assembly with a new one to accept larger OD cable, thus essentially not really modifying their product in a way thats not going to compromise anyone or put anyone at risk.

author: Zero999
author_rank: Super Contributor
timestamp: August 01, 2017, 06:24:17 pm
content: Quote from: hermit on August 01, 2017, 05:45:17 pmThat grounding point is a place to connect the shields of screened cable, more than anything else. It's not a protective earth terminal. It's there for EMC purposes.

author: Specmaster
author_rank: Super Contributor
timestamp: August 01, 2017, 06:37:39 pm
content: Quote from: Hero999 on August 01, 2017, 06:24:17 pmHow would you do that then? The cables all come pre terminated with suitable plugs, ie., RCA phono or DIN plugs and the shields are already soldered into the plugs?

author: tronde
author_rank: Frequent Contributor
timestamp: August 01, 2017, 08:11:33 pm
content: Quote from: Gyro on July 31, 2017, 06:00:23 pmYou don't get it Gyro, You really don't get it.You don't want to understand what I say, and you do whatever you can to twist it as much as possible. Only you can tell why.I HAVE been very specific about the prerequisite for when we can use the 4/5mm as aguidewhen weevaluatethe risk for danger.I HAVE been very specific about the impact the environment will have on safety. I even gave an example for how small changes can change everything.I have NEVER claimed that these distances can be used as a guideline for new producs.I have used them as an EXAMPLE for why normal mains voltages are usually not extremely dangerous as many seems to believe.No need to tell me about contamination. I made a living out of repairing TVs long time ago. Heavy smokers without knowledge of vacuum cleaners are no strangers to me. But, I do really think I mentioned dustfree environment as a prerequisite, didn't I? Yes, I do really think I did so. Don't know why you bring it up again.When it comes to transients: Yes, they exist. They have even considered them when they made the standards. The funny thing is that both office equipment and AV-equipment is meant to be used in the same category-II overvoltage environment. That is what you have in an office or a normal home, so the transients will be the same. Both types of equipment are usually permanently connected to mains as well. I guess you are aware of this?The real difference between those two types of equipment, is the environment. This is why they increased the safety margins on AV-equipment. This is not the same as office equipment, or anything following that standard, is close to unsafe when used in theintendedenvironment. I have said it several times, but again, you prefer to twist it as much as possible.*This is about Europe, but it seems like most countries follow this route when they upgrade their laws.In Europe, safety for most electrical equipment is regulated by the Low Voltage Directive. The LVD is "the law" about this here.The LVD says very little about specific technical things. The LVD is based on "function" instead of details. The LVD lists some "functions" that are vital for a product. Most important is (in free wording) "not cause damage to any person", "not cause any damage to animals" and "not cause any damage to buildings". Then, they say, it's up to you to figure out how to give these "functions" to your product.They know this can be difficult, so they reach out an helping hand. They tell you that if you build your product in accordance to what is known as "harmonised standards" (those with a name beginning with EN), you will most likely get it right, and be OK.If you want to sell in the EU, you must prove that your product is safe. That is why you must sign a "declaration of conformity."When you sign this declaration, you don't sign for being compliant with a standard, as many believe. You sign for being compliant with the LVD.The funny thing about this, is that it is usually possible to be legally in compliance with a directivewithoutany relation between the product and any standard.When you sign this "declaration of conformity" you must also tell why you think you are OK. This is why you will have to list the relavant standards you have used. But, it is possible to skip standards in most instances. Then you must prove your product is safe in another way. It is sometimes done, but mostly for other directives than the LVD becaude of the cost and difficulties involved.Because the LVD is based on "function", it is sometimes possible to "cherry-pick" standards without being caught for wrong-doing. They do so on AV-equipment and office equipment for instance.I have got some spoken info on parts of the upcoming combined standard for AV and office equipment. It is not the final version, so it can be something different in the final version. I was told that they have shaved off 1 mm on each of the 4 / 5 mm distances that has created so much noise...

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: August 01, 2017, 09:06:31 pm
content: I think you'll find a metal case is OK standardswise provided that all mains wiring is double insulated. That is, the normal wiring insulation plus a boot or sheath of some kind. Looks like this has some parts that are not even single insulated though, so I doubt if it would get approval.Actually the electrical standards situation in the EU is a mess. Each country has its own rules, and even where an item meets the spec of one country it may have to be retested for sale in another. This is a deliberate policy to try to block imports from other EU members.Audio separates should be grounded at one point in the stack, but not multiply grounded because doing so effectively creates a one-turn transformer which picks up hum. Safest solution here though, is a stout grounding wire on the case. I'd also think about some heatshrink or a boot over those open live connections.

author: hermit
author_rank: Frequent Contributor
timestamp: August 01, 2017, 09:22:01 pm
content: Quote from: IanMacdonald on August 01, 2017, 09:06:31 pmAt first glance I read mental case. I think this thread is getting to me.

author: Specmaster
author_rank: Super Contributor
timestamp: August 01, 2017, 11:48:36 pm
content: Wow, this thread has generated some discussion and raised some interesting points along the way and basically as I see it, taking away people's different interpretation of the rules and guidelines people who like me have come from the electrical faction want to see the case grounded and those from the electronics faction say that it not designed to be grounded and I for one can see both sides of the discussion. It really makes some interesting reading and that is the good thing about this forum is that there is a healthy participation in most threads and the trick is to keep an open mind and be prepared to have your own stance on issues altered as a result of the sometimes overwhelming evidence in support of one view or another.

author: Electro Detective
author_rank: Super Contributor
timestamp: August 02, 2017, 01:39:01 am
content: It's been a great threadIMVHO: Once you join that component in it's stock form (unmodified) with the RCA connectors to the rest of the system,it should satisfy electric and electronic minded concerned people and just work as it was designed to.No shocks, no tingle, no hum,...and no freaking out

author: John B
author_rank: Frequent Contributor
timestamp: August 02, 2017, 03:04:21 am
content: Quote from: Specmaster on August 01, 2017, 11:48:36 pmIndeed, in the beginning I was fairly adamant that I would ground the device. Now, I think Ill leave the unit sitting on a metal pedestal that just so happens to be grounded.

author: Unknown
author_rank: Unknown
timestamp: August 02, 2017, 04:10:50 am
content: Quote from: Specmaster on August 01, 2017, 06:37:39 pmTypically the turntable will have a separate EMC/signal "earth" wire, or even separate "earth" & "ground" connections (). You also occasionally see the same on cassette decks, etc (I've even got an early CD player that came with one).

author: jh15
author_rank: Frequent Contributor
timestamp: August 02, 2017, 05:21:31 am
content: * jh15 again throws water on the mating dogs.

author: Specmaster
author_rank: Super Contributor
timestamp: August 02, 2017, 08:17:15 am
content: Quote from: jh15 on August 02, 2017, 05:21:31 amDon't want any more puppies...

author: Gyro
author_rank: Super Contributor
timestamp: August 02, 2017, 10:39:27 am
content: Quote from: tronde on August 01, 2017, 08:11:33 pmActually tronde, I think we are actually in violentagreementon many things, certainly some items in your post above. It's a shame that you didn't respond to my second email yesteray regarding the Legal aspect as this really is the crux of the matter from my perspective, I think you might have agreed with quite a lot of that.I really do understand that you meant your 4/5mm is a "guide", I just don't think it helps with theLegalissues surrounding repair of the type of equipment this thread is about.It seems clear that we are approaching this from different directions, me from the manufacturing background and you from the repairer(?). It seems unlikely that we will ever fully agree on this, I guess we will have to live with that.You are correct that, in Europe, the Low voltage directiveis the 'blanket' safety requirement (let's not forget the EMC directive too), but it does rely to on equipment having met its specific prescribed EN safety standard. I amveryfamiliar with the signing of the Declaration of Conformity. You sign implicitly for LVD (and EMC) conformity, but that Declarationdoesalso explicitely specifiy the specific ENxxxx standards that the product complies with (and preferably has been independently tested against). [EDIT: See example in the attached link for reference:http://www.conformance.co.uk/info/declarationofcon.php#]As an aside, many countries outside the EU will also accept compliance to ENxxxx standards as an assurance of EMC / Safety performance. We shipped many products to the Middle East for instance and even some to Australia, also the Far East (manufactured there). North America of course is a different matter. Thankfully a market that was not of interest.I think we both agree that metal cased or metal chassis Class II consumer is a 'special case' it is for me at least. You won't find its like in Industrial or, medical. Most IT equipment is also grounded metal case, either that or separate mains adaptor.Being in a domestic environment makes it much more susceptible to foreign object insertion, liquid spills, other forms of contamination, as previously mentioned. To tell the truth, I have always been a little uncomfortable with them, even after designing them, however you must compete in the market. I have had frighting experiences of what can go wrong. As I mentioned, I have seen cases of all four mountings of an SMPS breaking off under mecanical shock (thankfully in prototype, but also seen in partial failures in other products). I have an innate distrust of SRBP board material being permitted in these products. I am uncomfortable with enlarged clearances being acceptable in place of intervening solid insulation. I am uncomfortable with the ventilation slot allowances, which can allow both introduction of slim (paperclips etc) conductive objects and airborn contaminants.Such concerns probably make me very sensitive to people suggesting smaller clearances as "guides" to electical safely, especially in a thread where the OP is talking about this category of product. I agree with you completely about the physics of electrical breakdown for the dimensions you stated... just not in the specific context of this thread.This (I think) just brings us to the Legal aspect of repair of this type of equipment. I think I stated my position very clearly in my last post. I don't think I need to add anything further. Maybe you have some comments on that post, maybe not. I can't see any possibility of compromising on that position. If you have a different angle on this then I think we must agree to differ.I hope that this goes some way towards clearing the air, or at least understanding between us, as this argument is counterproductive.

author: Specmaster
author_rank: Super Contributor
timestamp: August 02, 2017, 12:07:54 pm
content: I think I summed it up very nicely when I said in post #109 "We are no different to other so called experts, some of whom cannot even agree on the correct way to make a cup of tea."We see examples of that often on TV and in the newspapers and is especially true in the medical profession when 2 or more extremely well qualified doctors have differences of opinion on certain topics and this thread is no different.My own personal preference is that if the metal enclosure contains voltages that are derived from being connected to the ac supply, irrespective of the line voltage, unless that power source is via a wall wart, (power supply unit) that converts it to DC at a lower voltage nominally 24v or less, is that the metal should be grounded.I have over the years seen many examples of equipment from some respected makers around the world who presumably had designed their equipment to class II standards where the supply passes through nothing more than a rubber grommet to gain entry to the interior of the the item. Two names that spring to mind are Tech of Japan and Heathkit of USA, their kit is always in a metal case and not grounded. Tech as far as I'm aware only made electronic test gear such as signal generators and a lot of Heathkits products were aimed directly at the electronics world with much of their products being test gear as well. I have always automatically grounded these as a matter of my own personal safety if nothing else.

author: ebastler
author_rank: Super Contributor
timestamp: August 02, 2017, 12:18:42 pm
content: Quote from: Specmaster on August 02, 2017, 12:07:54 pmNo, I think this thread is worse. We have several "experts" who insist on discussing how to brew coffee, how to serve tea in a public restaurant, or whatever.Seriously, the present discussion is one of the most erratic ones I have seen on this forum yet -- not sure why.

author: Gyro
author_rank: Super Contributor
timestamp: August 02, 2017, 12:22:50 pm
content: Well I'm open to suggestions!

author: Nusa
author_rank: Super Contributor
timestamp: August 02, 2017, 01:24:22 pm
content: That bit about Heathkit isn't quite fair. Heathkit started making kits in 1947. Three-prong plugs in the US didn't exist until the 1960's. They weren't mandated until about 1970 (with old 2-prong installs grandfathered forever), which of course covers the real heydey of Heathkit. Many of the more modern kits WERE designed with 3-prong plugs. And then Heathkit got out of the kit business, so any US standards more recent than 1990 are irrelevant if you're pointing at them.Also, many of their more consumer-oriented kits had wood cases/cabinets with plastic knobs. The TV's, Organs, Stereos, and Clocks in particular.

author: Specmaster
author_rank: Super Contributor
timestamp: August 02, 2017, 01:52:14 pm
content: Quote from: Nusa on August 02, 2017, 01:24:22 pmOops sorry, I wasn't implying that they were of the 2 pin era at all, this I just don't know, their kits that were destined for the UK market as far as I know were also of 2 core wiring and we have had 3 pin plugs for years now, in fact the earliest 3 pin plug and socket was made by A. P. Lundberg & Sons of London around 1911 and in 1934 the 10th Edition of the IEE’s “Regulations for the Electrical Equipment of Buildings” introduced the requirement for all sockets to have an earth contact.

author: Specmaster
author_rank: Super Contributor
timestamp: August 02, 2017, 01:59:46 pm
content: Quote from: ebastler on August 02, 2017, 12:18:42 pmI think actually that we are in agreement here aren't we?Quote from: ebastler on August 02, 2017, 12:18:42 pmThats because everyone is passionate about their beliefs and thats is to be applauded surely?

author: tronde
author_rank: Frequent Contributor
timestamp: August 02, 2017, 05:39:52 pm
content: Quote from: Gyro on August 02, 2017, 10:39:27 amI think I understand why you made so many words out of many of my prevous posts, Gyro.Please spend some time reading this post before you reach for your keybord.When I read your latest long comment some dots join together.How I see this evolving over time:I wrote something.You started to read, and when my text gave some meaning, you just dropped the rest of the text I wrote.I say this, because what you write about differences in environment is almost exactly the same as I always have said. I wrote about many things that would invalidate the 4/5mm from being considered "safe", maybe I should have called it "not probably very dangerous" instead.It just seems like you never readthatpart of what I wrote. Regardless of how I tried to express myself, It was just as those words never existed to you. This is how I feel it.I must also say, that I don't think you deliberately dropped reading some parts of my text.To me, it seems like you sometimes face some problems with reading text when it has extra words that can modify the meaning of the first part of it.This is well known today, and it is believed that some 10-20% of male adults in the West thave some difficulties with this.I don't write this to upset you, Gyro. I have since long time ago felt that you are a nice guy, and that you want to be nice to people around you.I write this because I really feel you wold benefit from paying attention to your reading strategies. Reading strategies are usually not something we think about, they "just are there".But, sometimes it can be beneficial to spend some time on them. Many people are not aware of them at all, and many do not see that they can improve their reading.Since you seemed to misinterpret so much of what I wrote, and it caused so much noise, I do scincerely feel you should spend some time and see if some of this can have an origin in how you interpret text.< peace >You mention email(s ?). I have not got any emails about this. I never check the "allow send emails to me" button on forums, so I would not expect it to be possible sending some to me via the forum?

author: Gyro
author_rank: Super Contributor
timestamp: August 03, 2017, 08:59:59 am
content: Hi tronde,Thanks for your reply. Be assured that I read it thoroughly.I've taken some time re-reading this thread in its entirety, and then couple of times more! I really recommend doing the same exercise. It has certainly taken an interesting andwide rangingpath from the OP's specific question. I defy anyone to fully track who was disagreeing with who by the time it got to page 2! (singling out no names).There was also a very large diversion into the subject of shock and safety risk associated with 240V mains in general. That one is probably worth a thread all of it's own, though one that I would probably give a wide berth.I did indeed find your qualifications to the 4/5mm figures on page 1 but they rapidly became lost beside the large font of the figures themselves in subsquent disagreements. That is until you put them in highlighted quotes on page 4 .I certainly take on board your observations about my failing to fully read (maybe even being partially blind to) every detail of that you wrote. I will try to do better in future. I must get back into the habit of individually quoting particular points and phrases, both to ensure and demonstrate that I have read them. It's more effort but worth it to break up wall of text replies.Re-reading the thread fully, without the emotion, it actually doesn't look as bad as I had feared. It has certainly dragged out more specific and detailed information than might have otherwise been the case. Hopefully of benefit to any who have the patience to read through in future.Anyway, to the main order of business: <peace>Yes sorry, I actually meant posts when I wrote emails - a slip of the brain! I haven't tried to email or PM you.Chris

author: Specmaster
author_rank: Super Contributor
timestamp: August 03, 2017, 11:34:01 am
content: Hooray, peace is breaking out between these two gentlemenAll joking aside, personally I have learned a lot from these gentleman and I dare say, no doubt so have many others reading and maybe even contributing to this thread so it has not been in vain