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Odd wiring in tube ampmschematics
I would post this in the basics group but it seems like there are more
responders here. Anyway, I have been looking at DIY single ended tube amp schematics recently. These are modern schematics using grounded power cords. And several have in common that the power switch is in the neutral line and the fuse in the hot. Wouldn't it be safer to have both the switch and fuse in the hot line? Thanks, Eric |
Odd wiring in tube ampmschematics
On Thu, 6 Dec 2018 11:36:53 -0800, John Robertson
wrote: On 2018/12/06 10:04 AM, wrote: I would post this in the basics group but it seems like there are more responders here. Anyway, I have been looking at DIY single ended tube amp schematics recently. These are modern schematics using grounded power cords. And several have in common that the power switch is in the neutral line and the fuse in the hot. Wouldn't it be safer to have both the switch and fuse in the hot line? Thanks, Eric For a 3 wire power system (with grounded chassis) that is incorrect as you suspect. For a two wire power then it is correct to have the switch on one side of the line and the fuse on the other as you don't know (unless the plug is polarized) which side is hot when plugged in. John :-#)# Ahh, that makes sense. I bet a lot of the designs copied existing older circuits where possible. Thanks, Eric |
Odd wiring in tube ampmschematics
On Thursday, December 6, 2018 at 2:37:02 PM UTC-5, John Robertson wrote:
For a 3 wire power system (with grounded chassis) that is incorrect as you suspect. For a two wire power then it is correct to have the switch on one side of the line and the fuse on the other as you don't know (unless the plug is polarized) which side is hot when plugged in. There is that. I tend to replace line cords with those using polarized plugs, if possible, and then keep the fuse (if any) and switch on the 'hot' line. General, I would not add a fuse to an AA5, but rather use a purpose-made fused box, plugging the radio into that. In such a way, the fuse level could be varied, and the hot will surely be fused in any case. ' The problem with converting old amps to 3-wires is a matter of hum-loops. Just don't do it. Polarizing the plug is fine. There is a very long explanation of why this is so, but "hum loop" should be enough. But, at no time with a repaired/restored amp should power exist on the transformer or chassis with the power switch in the "OFF" position. Full Stop. Peter Wieck Melrose Park, PA |
Odd wiring in tube ampmschematics
On Thursday, 6 December 2018 17:59:08 UTC, wrote:
I would post this in the basics group but it seems like there are more responders here. Anyway, I have been looking at DIY single ended tube amp schematics recently. These are modern schematics using grounded power cords. And several have in common that the power switch is in the neutral line and the fuse in the hot. Wouldn't it be safer to have both the switch and fuse in the hot line? Thanks, Eric You're right, that is obsolete practice from the days of unpolarised ungrounded power cords. I don't think it ever had any advantage from a safety perspective, it was just fractionally easier to terminate the mains cord onto a switch & a fuse. NT |
Odd wiring in tube ampmschematics
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Odd wiring in tube ampmschematics
On Thursday, 6 December 2018 22:03:43 UTC, Ralph Mowery wrote:
In article , says... For a 3 wire power system (with grounded chassis) that is incorrect as you suspect. For a two wire power then it is correct to have the switch on one side of the line and the fuse on the other as you don't know (unless the plug is polarized) which side is hot when plugged in. I am getting into this late. When replacing the line cord on an older 2 wire cord ( no ground) with a 3 wire grounded cord, which is the perferred method ? Go from the hot wire to the switch or the fuse first, then to the other and transfromer , back to neutral ? Of course the grounded pin on the plug goes to the chassis and the 120 VAC is isolated from the chassis by the transformer. Several of us were discussing this the other day, but none of us knew for sure which should come first, switch or fuse in the 3 wire 120 vac equipment. It did seem that in the older ARRL Handbook the 2 wire cords had the fuse on one side and the switch on the other side of the transformer. Fuse & switch should both be on the live side. Fuse should come first, switches do sometimes short. Wires to switches can also come adrift. NT |
Odd wiring in tube ampmschematics
On 6-12-2018 23:03, Ralph Mowery wrote:
In article , says... For a 3 wire power system (with grounded chassis) that is incorrect as you suspect. For a two wire power then it is correct to have the switch on one side of the line and the fuse on the other as you don't know (unless the plug is polarized) which side is hot when plugged in. I am getting into this late. When replacing the line cord on an older 2 wire cord ( no ground) with a 3 wire grounded cord, which is the perferred method ? Go from the hot wire to the switch or the fuse first, then to the other and transfromer , back to neutral ? Of course the grounded pin on the plug goes to the chassis and the 120 VAC is isolated from the chassis by the transformer. Several of us were discussing this the other day, but none of us knew for sure which should come first, switch or fuse in the 3 wire 120 vac equipment. It did seem that in the older ARRL Handbook the 2 wire cords had the fuse on one side and the switch on the other side of the transformer. A 2-pole switch would be the first thing I would add. |
Odd wiring in tube ampmschematics
Maybe your wall plus is not respecting the norm.
So, what you call neutral might the the phase line. To comply to safety rules, manufacturers must protect the phase line, not the neutral (VDE, UV, IEC, ANSI...). a écritÂ*: I would post this in the basics group but it seems like there are more responders here. Anyway, I have been looking at DIY single ended tube amp schematics recently. These are modern schematics using grounded power cords. And several have in common that the power switch is in the neutral line and the fuse in the hot. Wouldn't it be safer to have both the switch and fuse in the hot line? Thanks, Eric |
Odd wiring in tube ampmschematics
Maybe your wall plug is not respecting the norm.
So, what you call neutral should be the phase line. Seen from you, the phase should be on the right, neutral on the left (plug in the wall). It's easy to check, take a voltmeter (scale 500V AC), take one end (barefoot), and put the other one in the plug (each holes, one by one). You have no risk ; if it is the phase line , the meter should move a little. Don't forget that if you put the meter in Amperes, you will reach the cieling. To comply to safety rules, manufacturers must protect the phase line, not the neutral (VDE, UL, IEC, ANSI, ISO...). So your wall plug connexions might be inverted. Look165 a écritÂ*: Maybe your wall plus is not respecting the norm. So, what you call neutral might the the phase line. To comply to safety rules, manufacturers must protect the phase line, not the neutral (VDE, UV, IEC, ANSI...). |
Odd wiring in tube ampmschematics
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Odd wiring in tube ampmschematics
I said with a voltmeter 500 VAC (some 1MOhms) in between you and the phase,
The measure should show about 5-10 VAC if you don't come from the shower but barefoot. The neutral is easy to check ; around 5-10VAC betweent neutral and ground (a water pipe for instance or a heater in case of collective heating). Fox's Mercantile a écritÂ*: On 12/6/18 12:04 PM, wrote: I would post this in the basics group but it seems like there are more responders here. Anyway, I have been looking at DIY single ended tube amp schematics recently. These are modern schematics using grounded power cords. And several have in common that the power switch is in the neutral line and the fuse in the hot. Wouldn't it be safer to have both the switch and fuse in the hot line? Thanks, Eric Almost all of those projects aren't done by engineers. They're done by people parroting one another. Back in the "good old days" of two wire non-polarized line cords, the standard procedure was one side went to the fuse, if it had one, the other side went to the switch. There was no engineering behind that decision, it was strictly manufacturing, "We need one less tie point." Look at it as a series loop. It doesn't matter the sequence that anything is connected in. Three wire line cords: Hot, to fuse holder (The point at the far end of the fuse) then to the power switch. Not that you should rely on an open fuse to keep your fingers off the hot side of a line inside a chassis. |
Odd wiring in tube ampmschematics
On Friday, December 7, 2018 at 8:47:44 AM UTC-5, Look165 wrote:
I said with a voltmeter 500 VAC (some 1MOhms) in between you and the phase, The measure should show about 5-10 VAC if you don't come from the shower but barefoot. The neutral is easy to check ; around 5-10VAC betweent neutral and ground (a water pipe for instance or a heater in case of collective heating). If you are seeing an actual 5 - 10 VAC on the meter between neutral and ground in a household system, and the wiring is otherwise to-code (US NEC), something is wrong. Peter Wieck Melrose Park, PA |
Odd wiring in tube ampmschematics
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Odd wiring in tube ampmschematics
On Friday, December 7, 2018 at 12:49:02 PM UTC-5, Fox's Mercantile wrote:
Probably under sized wiring, or a bad connection somewhere along the neutral line. A couple of volts is normal due to the normal voltage drop in a conductor. Maybe so. But that is enough to play havoc with such unimportant items as pacemakers, not to mention what it might do to audio and video equipment. Peter Wieck Melrose Park, PA |
Odd wiring in tube ampmschematics
On Friday, 7 December 2018 18:13:16 UTC, wrote:
On Friday, December 7, 2018 at 12:49:02 PM UTC-5, Fox's Mercantile wrote: Probably under sized wiring, or a bad connection somewhere along the neutral line. A couple of volts is normal due to the normal voltage drop in a conductor. Maybe so. But that is enough to play havoc with such unimportant items as pacemakers, not to mention what it might do to audio and video equipment. Peter Wieck Melrose Park, PA how would a couple of volts mains drop have an effect on pacemakers? NT |
Odd wiring in tube ampmschematics
"If you are seeing an actual 5 - 10 VAC on the meter between neutral and ground in a household system, and the wiring is otherwise to-code (US NEC), something is wrong. "
Not true. If one side is loaded heavily that's what happens. One house, window AC units, for example had 25 volts on the neutral because all the A/C units were on one side of the line. In that house it was because the job wasn't planned right. It was code but a **** job. And nothing wrong. This can also happen in some older houses when the main neutral coming in is a smaller gauge than the hots. Even if not. If you put too much load on one side it happens. Then if you blow the neutral fuse, which should not be there logically, it can throw 240 volts into everything on the lightly loaded side. Many houses around here are older. They did not anticipate all the load we have these days. I have had to change the lead in from the meter more than once, otherwise I would have had to put in like a 50 amp main or the job wouldn't be code. I got them ready for the service upgrade to 100 amps. Actually 100 amps is not all that much these days. Not enough if you have a hot tub/jacuzzi or an electric furnace. If you have both, double it to 200 amps. (then they will probably put in a peak load meter to pick your pocket more effectively) |
Odd wiring in tube ampmschematics
"how would a couple of volts mains drop have an effect on pacemakers? "
It won't. It also should not affect any audio or other equipment that is designed right. The only POSSIBLE problem might be turntable hum but even then... |
Odd wiring in tube ampmschematics
On Saturday, 8 December 2018 03:57:57 UTC, wrote:
"how would a couple of volts mains drop have an effect on pacemakers? " It won't. It also should not affect any audio or other equipment that is designed right. The only POSSIBLE problem might be turntable hum but even then... All domestic mains current loads are balanced, ie live & neutral carry the same & opposite current, resulting in nearly zero magnetic field. Pacemakers, like any life-critical medical equipment, are designed & tested to meet harsh real-world conditions & keep going. NT |
Odd wiring in tube ampmschematics
Ralph Mowery wrote:
I am getting into this late. When replacing the line cord on an older 2 wire cord ( no ground) with a 3 wire grounded cord, which is the perferred method ? Go from the hot wire to the switch or the fuse first, then to the other and transfromer , back to neutral ? Of course the grounded pin on the plug goes to the chassis and the 120 VAC is isolated from the chassis by the transformer. Several of us were discussing this the other day, but none of us knew for sure which should come first, switch or fuse in the 3 wire 120 vac equipment. ** I would opt for switch first, then fuse. This is for the benefit of silly owners who like to swap back panel AC fuses while the item is plugged in - relying on the switch to isolate both ends contacts on the fuse holder. Something that needs to be checked, cos only some fuse holders do this. |
Odd wiring in tube ampmschematics
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Odd wiring in tube ampmschematics
says... All domestic mains current loads are balanced, ie live & neutral carry the same & opposite current, resulting in nearly zero magnetic field. Pacemakers, like any life-critical medical equipment, are designed & tested to meet harsh real-world conditions & keep going. Nope: The neutral carries the "difference current" in the legs of a split phase system. It can be 180 or -180 out of phase (Said for ease of understanding).. It can also be zero, but not likely, The "difference current" is more accurate. While voltage is usually sinusoidal, current doesn't have to be. Voltage is what's regulated. inductive loads are one matter, but laptop switching power supplies is another. |
Odd wiring in tube ampmschematics
Ron D. wrote:
All domestic mains current loads are balanced, ie live & neutral carry the same & opposite current, resulting in nearly zero magnetic field. Pacemakers, like any life-critical medical equipment, are designed & tested to meet harsh real-world conditions & keep going. Nope: ** Fraid it is a yep. Any mains appliance returns the same current down the neutral conductor it drew from the active. This mean very little mag field is generated by the appliance's own lead, assuming the two wires are closely paired or twisted. .... Phil |
Odd wiring in tube ampmschematics
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Odd wiring in tube ampmschematics
On 12/9/18 3:14 PM, Ralph Mowery wrote:
One is thinking of a 240 volt system with 2 hots and the neutral, whrere the neutral can have almost any ammount of current on it up to being equal to what one side of the hot is using (120 volt devices). This is one of fallacies here in Ranger. Around here, the thought is the Neutral to the breaker panel from the meter can be smaller because it's not going to carry ALL of the current because there will be an offsetting current from the other hot leg. They also tend to under size everything, because, you know, copper is expensive. For example, my house has a 200 Amp service. That should be #000 on all three legs and #4 for the ground. When I got here, it was two #4 on the hots, #6 on the neutral and #10 for the ground. That was one of the first things I fixed. -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
Odd wiring in tube ampmschematics
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Odd wiring in tube ampmschematics
On 10/12/18 8:14 am, Ralph Mowery wrote:
In article , says... All domestic mains current loads are balanced, ie live & neutral carry the same & opposite current, resulting in nearly zero magnetic field. Pacemakers, like any life-critical medical equipment, are designed & tested to meet harsh real-world conditions & keep going. Nope: ** Fraid it is a yep. Any mains appliance returns the same current down the neutral conductor it drew from the active. This mean very little mag field is generated by the appliance's own lead, assuming the two wires are closely paired or twisted. I think you all are compairing apples and oranges. One is thinking of a 240 volt system with 2 hots and the neutral, whrere the neutral can have almost any ammount of current on it up to being equal to what one side of the hot is using (120 volt devices). Phil and the other are probably talking about a 120 volt device that has only a hot and neutral. Which in that case the neutral must have the same ammount of cuttent as the hot wire, unless there is a problem. Phil lives in Sydney. We use 240V single phase wiring, with a single hot and a single neutral grounded at the panel. The RCD protection trips if the currents on hot and neutral differ, even by milliamps for milliseconds. Some (few) buildings have two separate 240V phases wired to different circuits inside the house, but nothing gets connected between the phases. Clifford Heath. |
Odd wiring in tube ampmschematics
Ralph Mowery wrote:
Nope: ** Fraid it is a yep. Any mains appliance returns the same current down the neutral conductor it drew from the active. This mean very little mag field is generated by the appliance's own lead, assuming the two wires are closely paired or twisted. I think you all are compairing apples and oranges. One is thinking of a 240 volt system with 2 hots and the neutral, whrere the neutral can have almost any ammount of current on it up to being equal to what one side of the hot is using (120 volt devices). ** If a 240V load is connected across the two phases, then the current is each wire is the same. The principle is simple: a current carrying loop that is closed down on itself ( ie the wires are paralleled) or twisted cannot radiate a mag field. ..... Phil |
Odd wiring in tube ampmschematics
On Sunday, 9 December 2018 19:14:44 UTC, Ron D. wrote:
tabby says... All domestic mains current loads are balanced, ie live & neutral carry the same & opposite current, resulting in nearly zero magnetic field. Pacemakers, like any life-critical medical equipment, are designed & tested to meet harsh real-world conditions & keep going. Nope: The neutral carries the "difference current" in the legs of a split phase system. It can be 180 or -180 out of phase (Said for ease of understanding). It can also be zero, but not likely, The "difference current" is more accurate. While voltage is usually sinusoidal, current doesn't have to be. Voltage is what's regulated. inductive loads are one matter, but laptop switching power supplies is another. I think you'll find house sockets are wired single phase. NT |
Odd wiring in tube ampmschematics
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Odd wiring in tube ampmschematics
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Odd wiring in tube ampmschematics
On Monday, 10 December 2018 11:42:17 UTC, Fox's Mercantile wrote:
On 12/10/18 4:04 AM, tabbypurr wrote: On Sunday, 9 December 2018 19:14:44 UTC, Ron D. wrote: tabby says... All domestic mains current loads are balanced, ie live & neutral carry the same & opposite current, resulting in nearly zero magnetic field. Pacemakers, like any life-critical medical equipment, are designed & tested to meet harsh real-world conditions & keep going. Nope: The neutral carries the "difference current" in the legs of a split phase system. It can be 180 or -180 out of phase (Said for ease of understanding). It can also be zero, but not likely, The "difference current" is more accurate. While voltage is usually sinusoidal, current doesn't have to be. Voltage is what's regulated. inductive loads are one matter, but laptop switching power supplies is another. I think you'll find house sockets are wired single phase. NT Actually, the term "Split Phase" is accurate. The source is a center tapped 240 volt winding. -180 0 +180 degrees. Either side to center (neutral) is 120v, and across both sides (hot) is 240v. The usual problem is when people insist on calling it 2-phase due to the +/- nature of it. It is not, the primary is single phase. 3 phase has an angle between each phase of 360/3 = 120 degrees. 2 phase has an angle between each phase of 360/2 = 180 degrees. And that's what you have with the US domestic 120/240 system. The real problem occurs in a 3-phase Wye system. A-N, B-N and C-N are each 120 volts. Until someone who doesn't know how it works, takes A-B and tells the consumer it's 240v. And then typically table saws go up in flames, because they REALLY do no like running at 208 volts with a 120 instead of 180 phase shift across the windings. Naturally some people don't understand some things, nothing new there. NT |
Odd wiring in tube ampmschematics
On 12/10/18 6:01 AM, Look165 wrote:
120*(3^^0.5) gives 207V, not 240. 207.84 or commonly called 208. I said uneducated electricians THINK that two 120v phases running 120 degrees instead of 180 degrees apart equals 240 volts. As a service manager in a tool store, I had to explain that running a 5 HP table saw motor on 208 volts was NOT covered under warranty and they should make their "electrician" pay for the repairs. -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
Odd wiring in tube ampmschematics
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Odd wiring in tube ampmschematics
On Monday, 10 December 2018 16:58:22 UTC, Fox's Mercantile wrote:
On 12/10/18 6:22 AM, tabbypurr wrote: On Monday, 10 December 2018 11:42:17 UTC, Fox's Mercantile wrote: Actually, the term "Split Phase" is accurate. The source is a center tapped 240 volt winding. -180 0 +180 degrees. Either side to center (neutral) is 120v, and across both sides (hot) is 240v. The usual problem is when people insist on calling it 2-phase due to the ± nature of it. It is not, the primary is single phase. 3 phase has an angle between each phase of 360/3 = 120 degrees. Correct. 2 phase has an angle between each phase of 360/2 = 180 degrees. And that's what you have with the US domestic 120/240 system. Absolutely NOT. That is center tapped single phase. It's one of the 3 phase distribution system's phases, centre tapped, that is its source. That does not change the fact that it's 2 phase. In the early days of electrical generation, there was 2-phase, but the two phases were offset by 90 degrees. I've read various times of 2 phase systems with 180 degree offset, but not seen 90 degrees. NT |
Odd wiring in tube ampmschematics
OK - I am in an unique position he I actually have worked with true 2-phase power, developed in the 1920s before 3-phase was well-established, as a means to provide off-set to start motors. Also pretty much confined to Philadelphia and Baltimore, being the two major cities in what became the PMJ Interconnect.
From PECO Tariffs: Two-phase power is where the two phases are 90° apart. This is a four (4) wire system, and the neutral currents do not cancel even if the system is in balance. Hence the need for four (4) wires. I am surprised that so many went after the remark of audio and pacemakers. But here goes: Pacemakers will accept all sorts of RF and other interference today - a vast improvement from the days when merely walking past a vintage microwave (in operation) would cause troubles. But the modern pacemaker/defibrillators do not like stray currents in the body, as they may be taken as an event. If there is as much as a few volts difference between the NEUTRAL and the GROUND, and an individual so-equipped steps into that difference, that could be enough to trip the defib-function. Not (usually)fatal, but quite painful. Just ask the guy up on the 10th floor designing temporary artificial hearts - between restoring vintage Porsches. He will talk the paint off a board if given a chance - and I am sufficiently intrigued by what he does to give him those chances. And, of course, there are hum-loops caused by stray currents. Peter Wieck Melrose Park, PA |
Odd wiring in tube ampmschematics
In article ,
says... 3 phase has an angle between each phase of 360/3 = 120 degrees. 2 phase has an angle between each phase of 360/2 = 180 degrees. And that's what you have with the US domestic 120/240 system. The real problem occurs in a 3-phase Wye system. A-N, B-N and C-N are each 120 volts. Until someone who doesn't know how it works, takes A-B and tells the consumer it's 240v. And then typically table saws go up in flames, because they REALLY do no like running at 208 volts with a 120 instead of 180 phase shift across the windings. Naturally some people don't understand some things, nothing new there. Some do not understand that by definition and the way it is generated, 2 phase power is 90 deg out of phase, not 180. There for in the US the common feed of 240 and 120 volts can not be 2 phase. https://en.wikipedia.org/wiki/Two-phase_electric_power |
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