Hi,
Presumably you mean that there is voltage relative to earth.
This is one of my pet subjects, and one I've been meaning to expound on for some time.
There are 2 classes of equipment, known differently in different world area's, but nevertheless the classes remain the same:
Class 1: Equipment that can have conductive exterior, and single insulation. Any conductive surfaces must be connected to earth.
Class 2: Equipment that has double insulation and needs no earth. It may, in special cases, have limited conductive exterior parts.
In the case of valve amplifiers, it is hard to make one that conforms to Class 2*, so they must fall into Class 1.
*This is because even if full insulation is provided, the input and output connectors are a potential hazzard.
Also, there are many possibilities for faults developing that may cause the chassis to rise to a hazardous voltage.
In the UK and many country's, all mains outlets are provided with a safety earth. Where provided, this can be used to ensure safety.
However there are some European countries (and possibly others elsewhere) where no safety earth is available in the rooms where equipment is used.
It is my professional opinion that use of valve (tube) equipment in these places is potentially unsafe. My reasoning is this:
A fault. capacitive coupling, or leakage can cause the chassis or external parts to rise to a hazardous potential. Although the area might be designated as an earth free area, there are always earths. Examples are aerial (antenna) connections, central heating radiators, general plumbing, metal windows.
Bearing the above paragraph in mind, I would caution against the use of any high voltage equipment, valve/tube or SS unless a reliable earthing system can be guaranteed.
Right. I've said my piece
Have a snigger, but it IS important.
Anyway, Eduard: check the earthing...
Cheers,
Presumably you mean that there is voltage relative to earth.
This is one of my pet subjects, and one I've been meaning to expound on for some time.
There are 2 classes of equipment, known differently in different world area's, but nevertheless the classes remain the same:
Class 1: Equipment that can have conductive exterior, and single insulation. Any conductive surfaces must be connected to earth.
Class 2: Equipment that has double insulation and needs no earth. It may, in special cases, have limited conductive exterior parts.
In the case of valve amplifiers, it is hard to make one that conforms to Class 2*, so they must fall into Class 1.
*This is because even if full insulation is provided, the input and output connectors are a potential hazzard.
Also, there are many possibilities for faults developing that may cause the chassis to rise to a hazardous voltage.
In the UK and many country's, all mains outlets are provided with a safety earth. Where provided, this can be used to ensure safety.
However there are some European countries (and possibly others elsewhere) where no safety earth is available in the rooms where equipment is used.
It is my professional opinion that use of valve (tube) equipment in these places is potentially unsafe. My reasoning is this:
A fault. capacitive coupling, or leakage can cause the chassis or external parts to rise to a hazardous potential. Although the area might be designated as an earth free area, there are always earths. Examples are aerial (antenna) connections, central heating radiators, general plumbing, metal windows.
Bearing the above paragraph in mind, I would caution against the use of any high voltage equipment, valve/tube or SS unless a reliable earthing system can be guaranteed.
Right. I've said my piece
Have a snigger, but it IS important.Anyway, Eduard: check the earthing...
Cheers,
Hi,
As much as I hate to say it...most continental European countries only have dedicated earthing in kitchens or other places where washing machines and such are kept.
Living rooms in buildings older than, say, 20 years often don't have any three pronged earthed outlets.
Easy enough to solve as you pointed out.
And lucky me has split phase mains for free as does the better part of Belgium it would seem.
Ed,
The reason why it dissapears when measuring is probably because the meter itself drains it to earth.
As a little tweak, once you have a dedicated earth, you should remeasure the residual potential on the chassis referenced to earth with nothing else connected to that mains spur.
Compare residual chassis voltage depending on plug polarity and mark the plug for the lowest leakage current.
This is best done at the persons' home since mains polarity isn't necessarily the same.
Repeat for all the gear in the audio chain, one by one and enjoy the free lunch.
Cheers,
As much as I hate to say it...most continental European countries only have dedicated earthing in kitchens or other places where washing machines and such are kept.
Living rooms in buildings older than, say, 20 years often don't have any three pronged earthed outlets.
Easy enough to solve as you pointed out.
And lucky me has split phase mains for free as does the better part of Belgium it would seem.
Ed,
The reason why it dissapears when measuring is probably because the meter itself drains it to earth.
As a little tweak, once you have a dedicated earth, you should remeasure the residual potential on the chassis referenced to earth with nothing else connected to that mains spur.
Compare residual chassis voltage depending on plug polarity and mark the plug for the lowest leakage current.
This is best done at the persons' home since mains polarity isn't necessarily the same.
Repeat for all the gear in the audio chain, one by one and enjoy the free lunch.
Cheers,
Hi,
That is one way to determine the polarity of the mains.
Now, it could very well be that the polarity at the powerXformer primary side is reversed.
Other causes could be leaky caps inside the amps amongst other things.
Ed, I remember you brought this same problem up about a year ago. Could you be more specific on how much voltage/current is measured with respect to ground?
Regards,
That is one way to determine the polarity of the mains.
Now, it could very well be that the polarity at the powerXformer primary side is reversed.
Other causes could be leaky caps inside the amps amongst other things.
Ed, I remember you brought this same problem up about a year ago. Could you be more specific on how much voltage/current is measured with respect to ground?
Regards,
Hallo Frank,
I don't remember asking it on this forum. I will ask my friend if he can measure the tension but i remember he did tell me it is really high. He uses a Hiraga 20 watt transistor amp and a Croft tube preamp. I think the problem is caused by the electrical system in his house. We will see. Maybe it is a good idea to connect everything in somebody's else house? Thanks so far. Ed P.s. maybe i will try to use some panasonic foil caps in my 600 hertz filter. I have enough others in stock to combine it to this value but i think it is better to use only one and not a combination.
I don't remember asking it on this forum. I will ask my friend if he can measure the tension but i remember he did tell me it is really high. He uses a Hiraga 20 watt transistor amp and a Croft tube preamp. I think the problem is caused by the electrical system in his house. We will see. Maybe it is a good idea to connect everything in somebody's else house? Thanks so far. Ed P.s. maybe i will try to use some panasonic foil caps in my 600 hertz filter. I have enough others in stock to combine it to this value but i think it is better to use only one and not a combination.
eduard said:
Typically when one sees voltage on the neutral at the plug it is an indication of a floating Neutral. The bond is lost between neutral and ground at the pole transformer which causes the voltage to chase the load throughout the house. This can lead to backfeeding through the 2 pole devices in the home with dimming lights and fans running super fast or agonizingly slow. Have your friend seek a competent electrician to rectify this problem.
Hi Frank;
>>>...Now, it could very well be that the polarity at the powerXformer primary side is reversed...<<<
FWIW I had that happen with my last (in both senses of the word) storebought amp. And yes, that chassis would drift up quite a ways. The polarity of the cord was reversed; so much for quality control.
All the best,
Morse
>>>...Now, it could very well be that the polarity at the powerXformer primary side is reversed...<<<
FWIW I had that happen with my last (in both senses of the word) storebought amp. And yes, that chassis would drift up quite a ways. The polarity of the cord was reversed; so much for quality control.
All the best,
Morse
Mains polarity...
This should not be an issue. There should be equal insulation on both terminals, and the chassis should not be allowed to drift to any potential. Otherwise, what happens in installations where there are 2 pin reversable mains connectors?
I am sure no one would use an un-earthed electrical appliance in their kitchen. Well an un-earthed amplifier chassis is potentially much more dangerous. It's true that 2 pin outlets are generally fitted in "earth free" areas, but few will live up to that name nowdays.
I would seriously urge you to get a 3 pin outlet fitted, for safety reasons. There may well be sonic improvements to be had too
This should not be an issue. There should be equal insulation on both terminals, and the chassis should not be allowed to drift to any potential. Otherwise, what happens in installations where there are 2 pin reversable mains connectors?
I am sure no one would use an un-earthed electrical appliance in their kitchen. Well an un-earthed amplifier chassis is potentially much more dangerous. It's true that 2 pin outlets are generally fitted in "earth free" areas, but few will live up to that name nowdays.
I would seriously urge you to get a 3 pin outlet fitted, for safety reasons. There may well be sonic improvements to be had too
Hi John;
Good point. I'd been happy enough to fix the cord and leave it at that but I should check the chassis earth - it MUST be poor to nonexistant for that to have happened. Embarrassed that I didn't think of that at the time. That amp was always a tad noisy anyway, not that I use it much now. It's on the 'spares rack'.
Good advice as always.
Thanks and all the best,
Morse
Good point. I'd been happy enough to fix the cord and leave it at that but I should check the chassis earth - it MUST be poor to nonexistant for that to have happened. Embarrassed that I didn't think of that at the time. That amp was always a tad noisy anyway, not that I use it much now. It's on the 'spares rack'.
Good advice as always.
Thanks and all the best,
Morse
Hi,
The reason I brought this up was not out of safety concern but rather as a tip for getting better performance at the cost of going to the polarity test procedure and wire everything up with correct mains polarity.
This assumes a power arrangement of Live (x VAC)- Neutral (0 VAC) and Earth (True ground).
In Eds' friend case something else is probably wrong since the difference in current through the chassis with correct or incorrect mains polarity is only a few tens of mA at best.
Cheers,
The reason I brought this up was not out of safety concern but rather as a tip for getting better performance at the cost of going to the polarity test procedure and wire everything up with correct mains polarity.
This assumes a power arrangement of Live (x VAC)- Neutral (0 VAC) and Earth (True ground).
In Eds' friend case something else is probably wrong since the difference in current through the chassis with correct or incorrect mains polarity is only a few tens of mA at best.
Cheers,
Mains voltage w.r.t. earth
Agreed, the insulation to chassis should be adequate from both terminals, but the stray capacitance is often different. Mains transformers are usually wound primary first, then secondary on top. This means that one end of the primary is close to the core, and the other remote. This difference in capacitances to chassis is why some Philips CD players sounded better when the the two pin mains plug was plugged in one way round rather than the other.
dhaen said:
Agreed, the insulation to chassis should be adequate from both terminals, but the stray capacitance is often different. Mains transformers are usually wound primary first, then secondary on top. This means that one end of the primary is close to the core, and the other remote. This difference in capacitances to chassis is why some Philips CD players sounded better when the the two pin mains plug was plugged in one way round rather than the other.
Who are "you fellows"?fdegrove said:Hi,
And that holds true for anything really, quite often, even with three pronged plugs, the leakage current will be higher one way or another.
It's worthwhile to check for this.
I'm a little surprised you fellows seem unaware of this.
Cheers,
The leakage due to transformer capacitance should be miniscule.
Hi EC8010;
>>>....the stray capacitance is often different...<<<
Thanks for explaining it! It really was bugging me, since I couldn't see any reason for that behaviour in that amp. The darn thing really did drift up quite a ways with that reverse wired cord (perhaps the connection to earth was a bit seedy in that cord as well...). Anyway, the info is much appreciated!
Hi frank;
>>>...I'm a little surprised you fellows seem unaware of this...<<<
I guess it just goes to show that no matter how much you know there's always something else out there to learn. The other explanation for my lapse would be the early onset of senility, so I think I shall choose the first explanation instead!!
All the best,
Morse
>>>....the stray capacitance is often different...<<<
Thanks for explaining it! It really was bugging me, since I couldn't see any reason for that behaviour in that amp. The darn thing really did drift up quite a ways with that reverse wired cord (perhaps the connection to earth was a bit seedy in that cord as well...). Anyway, the info is much appreciated!
Hi frank;
>>>...I'm a little surprised you fellows seem unaware of this...<<<
I guess it just goes to show that no matter how much you know there's always something else out there to learn. The other explanation for my lapse would be the early onset of senility, so I think I shall choose the first explanation instead!!
All the best,
Morse
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