Grounding old equipment

[tronde]

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.

Realism 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.

No, 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.

It's not that part I find abrasive. You wrote something I felt as badly worded and could easily be taken out of context.

Maybe 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.

[hermit]

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.

[Electro Detective]

I'm with hermit and Tronde on this,   

too much freaking out     that one dumbass numbskull amongst billions
is 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 Hades 


FWIW, I've opened and serviced hundreds, no.. thousands of domestic A/V (and professional) units like this, mostly constructed the same or very similar

Besides 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 house


If 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 rubber     
and so forth   


i.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..."   

[b_force]

Edit: and yes 240V AC will quite happily kill you under the right circumstances!

So 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)

[b_force]

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.

Realism 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.

No, 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.

It's not that part I find abrasive. You wrote something I felt as badly worded and could easily be taken out of context.

Maybe 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.

This reply should be a sticky, with capital letters and send to everyone on a daily basis
 

[tpowell1830]

The unit has been around since 1990 and is still in one piece... just  saying.

[Electro Detective]

The unit has been around since 1990 and is still in one piece... just  saying.

Same deal for the owner/s of posted unit, and their pets   

[Gyro]

@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. 

[b_force]

@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. 

Back 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 like tronde did 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.

[Gyro]

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.

[b_force]

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.

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.

No, 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. 

[Zero999]

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.

[Gyro]

No, 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.

If you check back to the actual phrase that you quoted and responded to so incoherently to in your post, it was:

Edit: and yes 240V AC will quite happily kill you under the right circumstances!

I don't call that a default statement that something is lethal and it certainly doesn't justify your:

So does a 9V battery!!!!!!!

As I advised you, you need to go back and read the drivel that you wrote.

[ebastler]

... 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)

I 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

[RGB255_0_0]

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.

[RGB255_0_0]

... 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)

I 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

Looks like shadow to me.

[Gyro]

... 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)

I 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

I 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.

[ebastler]

Looks like shadow to me.

Hmm, 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?

[RGB255_0_0]

The shadow matches the angle of the cables, particularly the white one. The light is probably directly above.

[Kleinstein]

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.

[Gyro]

Just to complete my response...

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 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.

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.

The 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!

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. 

Only 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!

[Zero999]

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.

[BBBbbb]

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.

[ebastler]

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.

Nothing better than a measured, well-balanced response to steer this thread back on track... 

[b_force]

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.

Ones 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 are NOT about 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.