Security: even with gainclones an important issue!
As we (most) connect our gainclones to the mains, we should be very good informed about the professional security rules and norms.
At least, we should be aware of them. Some members from this forum are very knowledgeable in this topic, others, like me, are absolutely no professionals and have some personal opinions, what could be dangerous. I remarked already very valuable statements about security and norms from Upupa Epops, in this forum. Maybe, it is a good advice for amateurs like me, to read his statements (they will follow soon).
Here, I beginn with the main part: the primary connection of my experimental amp in the actual status (bad example, dangerous!!!).
Must be a good start, to list the rules how to make a cabling like this safe.
For a long and secure life!
Franz
P.S.
Don't hesitate to show your "problem", solution and "bad" examples, like I do!
As we (most) connect our gainclones to the mains, we should be very good informed about the professional security rules and norms.
At least, we should be aware of them. Some members from this forum are very knowledgeable in this topic, others, like me, are absolutely no professionals and have some personal opinions, what could be dangerous. I remarked already very valuable statements about security and norms from Upupa Epops, in this forum. Maybe, it is a good advice for amateurs like me, to read his statements (they will follow soon).
Here, I beginn with the main part: the primary connection of my experimental amp in the actual status (bad example, dangerous!!!).
An externally hosted image should be here but it was not working when we last tested it.
Must be a good start, to list the rules how to make a cabling like this safe.
For a long and secure life!
Franz
P.S.
Don't hesitate to show your "problem", solution and "bad" examples, like I do!
Al
Yes, feel free to choose the best title for this topic. Why not change it to a permanent "top" topic?
It would be worth, for safety of every cloner, their families and future owners!
Beginners dont search for security, they have the head filled of other dreams! So, it would be very good to see not just valve amps have some security issues. Right in the top of this forum.
Franz
Yes, feel free to choose the best title for this topic. Why not change it to a permanent "top" topic?
It would be worth, for safety of every cloner, their families and future owners!
Beginners dont search for security, they have the head filled of other dreams! So, it would be very good to see not just valve amps have some security issues. Right in the top of this forum.
Franz
While having no qualifications (I’m currently a young engineering student) to legally work with mains power in my country, I do so none the less
Now in your pic, if would have heat shrink tubing covering all the bare wires plus hot melt glue around where the solder tabs enter the plug where the tubing doesn’t quite cover as I’ve once still been shocked by a switch where I managed to touch a tiny bit of the bare tab in there and it scares the life out of you (and literally if your unlucky)
So personally if it’s all covered up with adequate insulation and won’t come off easily (and electrical tape usualy does, i'd only use it for temporary use) then its safe in my opinion
Now in your pic, if would have heat shrink tubing covering all the bare wires plus hot melt glue around where the solder tabs enter the plug where the tubing doesn’t quite cover as I’ve once still been shocked by a switch where I managed to touch a tiny bit of the bare tab in there and it scares the life out of you (and literally if your unlucky)
So personally if it’s all covered up with adequate insulation and won’t come off easily (and electrical tape usualy does, i'd only use it for temporary use) then its safe in my opinion
The second topic in after primary/mains connection should be: the output side:
When and why should output connectors be isolated, so they cannot be touched?
Every reader would agree with me, it makes no sense to set a rule and then selling amps with removable isolation like this:
A bad joke, isn't it? As you cannot use the amp, without removing them!
Franz
When and why should output connectors be isolated, so they cannot be touched?
Every reader would agree with me, it makes no sense to set a rule and then selling amps with removable isolation like this:
An externally hosted image should be here but it was not working when we last tested it.
A bad joke, isn't it? As you cannot use the amp, without removing them!
Franz
And last, but not least, a very important part:
The central grounding of the box. Here my version:
Franz
The central grounding of the box. Here my version:
An externally hosted image should be here but it was not working when we last tested it.
Franz
YES excellent thread Franz!
I'll add a topic if I may.
Some people have the PSU in a separate box/case/chassis. The argument then is that there is no need to earth/ground the amplifier case as there is only the rail voltages inside.
But I was once told that it is possible to still get a mains voltage into the amplifier case, one example being suggested was in the case of a short across the primary and secondary coils of the transformer.
So, could somebody knowledgeable on this either confirm or correct the above?
I'll add a topic if I may.
Some people have the PSU in a separate box/case/chassis. The argument then is that there is no need to earth/ground the amplifier case as there is only the rail voltages inside.
But I was once told that it is possible to still get a mains voltage into the amplifier case, one example being suggested was in the case of a short across the primary and secondary coils of the transformer.
So, could somebody knowledgeable on this either confirm or correct the above?
Please, for security reasons, let the answers in this thread for really good informed people (maybe you are) but don't stop to ask safety questions here.
Statements like this are not what I want in this important thread:
... as most of us are already knowing. Sorry!
Every answer in this thread should be from an expert, because it concerns safety.
Upupa Epops, for example, will be back in a few hours and then begin (sorry, when I cause you some work, Upupa) I am quite sure, he will present us a basic list to start discussion.
Don't hurry, be safe! Lets build up this thread slowly, mainly with open questions, please.
Franz
Statements like this are not what I want in this important thread:
... as most of us are already knowing. Sorry!
Every answer in this thread should be from an expert, because it concerns safety.
Upupa Epops, for example, will be back in a few hours and then begin (sorry, when I cause you some work, Upupa
) I am quite sure, he will present us a basic list to start discussion.Don't hurry, be safe! Lets build up this thread slowly, mainly with open questions, please.
Franz
Nuuk
Anything that is not double insulated should be connected to mains ground. It is not mandatory for items with separate PSUs, at least in Europe, but devices that are made this way do have to pass certification to get the CE mark and be built in an electrically safe manner. As we, as diy'ers, don't have this independant checking system, then I would go for earthing everything on a matter of principle.
Franz
Excellent use of star washers and suchlike, but diyAudio regulars will tell you about my phobia of using solder joints for safety critical applications. Crimps rule in my book!
As for the output side, EU regulations state that you should not be able to come into contact with potential differences of more than 48V. With a standard audio amp this is easily possible across the output terminals.
The plugs in the ends of the binding posts are, I believe, to stop people from 110V countries pugging in mains plugs that have the same pin spacing. However, I could be wrong!
Anything that is not double insulated should be connected to mains ground. It is not mandatory for items with separate PSUs, at least in Europe, but devices that are made this way do have to pass certification to get the CE mark and be built in an electrically safe manner. As we, as diy'ers, don't have this independant checking system, then I would go for earthing everything on a matter of principle.
Franz
Excellent use of star washers and suchlike, but diyAudio regulars will tell you about my phobia of using solder joints for safety critical applications. Crimps rule in my book!
As for the output side, EU regulations state that you should not be able to come into contact with potential differences of more than 48V. With a standard audio amp this is easily possible across the output terminals.
The plugs in the ends of the binding posts are, I believe, to stop people from 110V countries pugging in mains plugs that have the same pin spacing. However, I could be wrong!
Be sure to discharge large (e.g. reservoir) capacitors before working. Very large or high voltage ones can easily store enough energy to set something alight, or give you a shock, or destroy a precious chip. Not a good idea to use a screwdriver for this, as it could damage the cap. A small, high power resistor is ideal.
Tie down long cables, especially one carrying mains voltage, so that if they should be chance become disconnected, they can't short with anything.
Tie down long cables, especially one carrying mains voltage, so that if they should be chance become disconnected, they can't short with anything.
I will update my "list", of course
You're welcome, to this list!Dont understand me wrong: I hope, Upupa (or you first?) will present us some kind of "checklist" (not just one point) about this first three topics, regarding safety.
From tube amps, with higher voltages, I am used, to insert resistors at every needed point, to discharge the caps after power off.
Franz
i see this advice a lot, but people seldom offer a suggestion for the resistor's ohm/watt value. what is "small"? what is "high power"? a beginner who doesn't yet know to discharge a cap, will also not know what "small, high power" means yet; everything is still too new for them to make a good guess here.
for advice like this in the thread, it would be very helpful to give an example value to make the meaning clear.
I am curious about using high quality glass in the chassis making process. For example when I study the boards of Peter and Brian's gainclone or the Pass diy amps or Pavel's PCB's I admire the fusion of both the internal design and construction techniques. Safety of course is paramount but when done correctly as I have noticed valve amplifiers will sometimes do they show the best of both worlds and was curious why we do not see more "SS" done this way. . Also, I heard that a enclosed "metal" chassis helps blocking interference, but I had just finished reading a thread that stated "completely enclosing the PS and amp is not as important as the proper balanceing and grounding techniques". I'm a bit new at this but studying hard, also getting ready to start my first project and I have been visualizing a glass enclosure on top of the alum chassis that shows off the construction as well. Any pitfalls here??? - Best.
I find that many projects do not earth their enclosure properly. Many will paint the enclosure walls before putting it together, then set their central earth point on the base of the enclosure. The paint between the heatsinks, front, top, sides isolates the main earth from these panels and creates a very poorly earthed enclosure. If a 240v wire rests on these unearthed components it won't blow the fuse, it'll just sit there until the user creates the path to earth.
- The correct earthing method is that the enclosure should be earthed on each removable section. At the very least make sure they are screwed together with bare metal touching.
- We also actually have to have the earth pin with a lock nut (2 nuts).
Theres loads more but I forgot most of my regulations because I'm no longer a 'practicing' A grade electrician but I would not ask for experts, I would ask for all opinions, so many people die from electric shock, often after 10 years that the product was purchased, do all DIY people think that far into the future?
My old teacher used to exclaim "no knickers!".... meaning always use an appropriate cable stripper otherwise 'knicked' cables will break and cause a fault situation.
Anyway - good thread, I don't think people realise how dangerous things can get sometimes.
- The correct earthing method is that the enclosure should be earthed on each removable section. At the very least make sure they are screwed together with bare metal touching.
- We also actually have to have the earth pin with a lock nut (2 nuts).
Theres loads more but I forgot most of my regulations because I'm no longer a 'practicing' A grade electrician but I would not ask for experts, I would ask for all opinions, so many people die from electric shock, often after 10 years that the product was purchased, do all DIY people think that far into the future?
My old teacher used to exclaim "no knickers!".... meaning always use an appropriate cable stripper otherwise 'knicked' cables will break and cause a fault situation.
Anyway - good thread, I don't think people realise how dangerous things can get sometimes.
since many beginners will read this thread, it may be helpful to link to a few detailed resourses.
http://www.ibiblio.org/obp/electricCircuits/DC/DC_3.html
http://sound.westhost.com/earthing.htm
http://www.bottlehead.com/loosep/Safety.htm
http://www.ibiblio.org/obp/electricCircuits/DC/DC_3.html
http://sound.westhost.com/earthing.htm
http://www.bottlehead.com/loosep/Safety.htm
Zen Light used light bulbs instead of power resistors, and they work as a replacement in other applications as well. I use a 60W/240V light bulb to discharge my poweramp capacitors. They have the advantage to give an indication of the discharging process.
Franz was declared me as " expert of safety ", but I am not specialist in this field. Electronic is my hobby, but job too, so I must know safety norms as all people which make the same
I also remeber you chiming in when people proudly presented their project pics and safety problems were visible to the forum members. Maybe that's why he thought of you.
Normally all the electrical safety rules are available in local libraries.
One thing that comes to mind when I see many of the finished projects here, is that people do not use proper wire for the high power connections. I have seen anything from speaker cable to "something from the parts box" of unknown origin.
Wire is not a big expense and it's available anywhere. It's a VERY bad place to save 5 USD.
Such approach is very dangerous, as quite a number of thick wires are not approved for mains, though they look reliable, and even less for 10-15A DC. To look reliable dosn't quite make it in such an application.
Make sure you know what type of wire you are using, and make very sure it's well within it's rating ( I usually multiply by a safety factor of at least 2). Personally I rarely use anything but glass or PTFE (teflon) insulated wire, if pushed hard silicone would be considered as well. PTFE and glass is mechanically very strong, and both are reasonably heat resistant (especially glass). With such types of wire there is a somewhat bigger safety margin than with the usual PVC mains installation wire.
Another mistake I have seen often is that people don't keep wires out of reach of sharp edges, as for instance I've seen a guy that just drilled a hole in the rear panel of an amp and pulled the mains wire through, without even an eyelet, leave alone stress relieve of some kind.
As allready mentioned earlier, mains joints must be crimped, as solder melts at 260C, that's not far enough from what you would see in an overload situation. This is also true for high power DC connections. In this case I have learned that high power means 2-3A.
I can't come up with more at this point, but I'm sure there is something I've forgotten.
Magura
Wire is not a big expense and it's available anywhere. It's a VERY bad place to save 5 USD.
Such approach is very dangerous, as quite a number of thick wires are not approved for mains, though they look reliable, and even less for 10-15A DC. To look reliable dosn't quite make it in such an application.
Make sure you know what type of wire you are using, and make very sure it's well within it's rating ( I usually multiply by a safety factor of at least 2). Personally I rarely use anything but glass or PTFE (teflon) insulated wire, if pushed hard silicone would be considered as well. PTFE and glass is mechanically very strong, and both are reasonably heat resistant (especially glass). With such types of wire there is a somewhat bigger safety margin than with the usual PVC mains installation wire.
Another mistake I have seen often is that people don't keep wires out of reach of sharp edges, as for instance I've seen a guy that just drilled a hole in the rear panel of an amp and pulled the mains wire through, without even an eyelet, leave alone stress relieve of some kind.
As allready mentioned earlier, mains joints must be crimped, as solder melts at 260C, that's not far enough from what you would see in an overload situation. This is also true for high power DC connections. In this case I have learned that high power means 2-3A.
I can't come up with more at this point, but I'm sure there is something I've forgotten.
Magura
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