WaynerN
Addicted Member
They are measuring DC voltage, not AC mains......
Three prong vs two.
- Thread starter Zygmo
- Start date
They are measuring DC voltage, not AC mains......
yessssssss, but in most cases, especially one with lights, is not the dc ground the SAME as the transformer center taps. remember when I said that the voltage on the case when properly plugged in will be 3-6ish volts to half the mains...
restorer-john
Addicted Member
Very often polarity is important in vintage gear.
The OP's amplifier (Marantz 1050) in all markets uses a DPST (double pole single throw) switch which disconnects or connects both the active and neutral and according to the service manual.
The OP's tuner (Marantz 2020) however uses a SPST (single pole single throw) switch which the neutral is also connected to earth via a resistor and a US convenience outlet. Polarity is important in this case. One way disconnects the active (as it should), the other way connects the active permanently and trickles current to earth via a high value resistor causing 'tingling' on the front panel metalwork and the power switch failing to do its job in isolating the active from the primary of the transformer. Any and all types of insulation failure/surge etc can then cause a failure resulting in a live casework situation with no return path except through associated components or the person touching the front panel or casework.
Our discussion in the other thread was not a "pissing contest", it was a discussion about standards, safety and the 'old' (and mostly unsafe) way of doing things in the vintage era, vs. correctly double insulated and of course properly earthed gear.
In this thread, Powertech's response is correct, considered and backed up with facts.
The simple fact of the matter is that most vintage 70s gear was poorly wired. It was a wild-west of standards around the world and the US sold gear had non-polarised plugs, single pole switches, death-caps to chassis and very little if any quality insulation or correct air gaps for primary wiring and little or no protection for live-chassis situations.
Thankfully, modern standards have improved out of sight and we can take advantage of that by being vigilant with old gear, repairing and bringing mains wiring up to standard where you have the skills and understanding to rectify poor practices of the past.
restorer-john
Addicted Member
See, it's statements like this one that are uninformed. You have no idea that much HiFi sold in markets other than yours was exactly the same US/military/general stock, unpacked by the distributors, voltage changed and rewired from 2 core single insulated US plugs to 3 core double insulated cable and earthed correctly to the chassis.
I have literally hundreds of pieces of gear from all manufacturers where this happened. Here's a few pics in a thread a while back where I articulate what happened here in Australia with general market gear. roll down to post #89
http://audiokarma.org/forums/index....kes-no-difference.808998/page-5#post-11313889
With the world market (multivoltage) gear floating all over the world now, thanks to eBay, it is essential that people familiarize themselves with what is correct in their country and don't make blanket statements that are misleading.
I have a NOS Pioneer A-717 sitting right here in its brown unmarked Mil box that was brought in by Pioneer Australia voltage switched and rewired from two to three core and earthed and distributed to Douglas HiFi through normal channels.
Properly designed gear doesn't suffer from ground loops.
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US does not have a "earth" system.
Our "ground" and "neutral" are the same path to the ground stake in the ground outside our buildings.
Connecting the "ground" line to the chassis is in effect making it part of the AC main circuit.
You are telling people to connect one of the AC lines to the metal chassis.
When the unit is energized, the chassis will be part of the AC circuit.
Gear that did not have a 3 wire originally was not made to work with 3 wires as the US grid is built.
The re-wired "earthed" system must be using a true separate ground that is not part of the current carrier.
Our "ground" and "neutral" are the same path to the ground stake in the ground outside our buildings.
Connecting the "ground" line to the chassis is in effect making it part of the AC main circuit.
You are telling people to connect one of the AC lines to the metal chassis.
When the unit is energized, the chassis will be part of the AC circuit.
Gear that did not have a 3 wire originally was not made to work with 3 wires as the US grid is built.
The re-wired "earthed" system must be using a true separate ground that is not part of the current carrier.
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You don't understand what you are saying here, or in the other post you referenced. The OP is in the US, and as with most consumer equipment, are not wired to both legs of the line. (not 240v, but 120v) In the US, both the neutral and the ground are bonded by code in the panel. I stand firmly behind what I said, as does UL and NEC. It's why UL approved cords have indexed neutral (larger) and NEMA 5 sockets are made the way they are.
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JP
7480 74111110101115
Ground doesn't carry current. Lots of material available on this.
WaynerN
Addicted Member
New home construction does not have the neutrals strapped to the ground any more. They are kept totally separate. Things change, Standards change.
biscuithead
Me likes the eargasm retroplasm...
So very wrong with this statement, if you are talking about the U.S.
Neutral is always bonded at first means of disconnect.
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yes it does. it absolutely does. even more material on that. starting the first day of class of EE curriculum. I recall day 1 of class: the prof ask, true or false, current follows the shortest path to ground
the answer, which incidentally I got right as I understood this from age 12 was false, it follows ALL paths to ground. (I repeat this over and over today and I could prolly count on one hand the number of people who get this right or even understand it) because everything has resistance (and hence the futile search for the perfect super conductor) there is current, no matter how small in every conductor
I know the argument was intended to be, that the ground is not meant to be current carrying and certainly not lethal, but there is current. heck, there is current in the ground simply because there is current in the hot and neutral (wrap your heads around that one.)
And no offense, but please peeps, try to understand ground loops and how and why they spring up. if I were to design something as ground loop free as I could make it using materials known to man, it would be the size and weight of a bank vault....that may not fit in your rack....just sayin
at some point, after your local step down transformer, center tape of your 220v is tied to the ground. standards do change, whoo boy do they and the standard is now *MORE THAN 1* bonding. since most gas lines are plastic and ditto water lines, you no longer have jaws to clamp on pipes. the means to produce a stable neutral earth bond are harder than ever.
recall if you will, how power plants are actually constructed, as they build it they excavate hundreds of acres and bury thick copper mesh and the Po-plant only transmits hot thru the wire. but but but, how does current return to the plant? is it magic? IT literally does use the ground, hence, the NAME.
mhardy6647
Lunatic Member
actually, there are perfect superconductors... the second law of thermodynamics limits their practicality (i.e., they're not really perpetual motion devices), but not their existence.
http://www-rjn.physics.ox.ac.uk/lectures/superconnotes10.pdf
http://www-rjn.physics.ox.ac.uk/lectures/superconnotes10.pdf
JP
7480 74111110101115
This is my thinking: Starting simply, assume chassis to ground (PE) and a transformer primary across hot and neutral. Minute leakage aside, there is no circuit between ground and the mains in the branch AC circuit.
Sure, but the return path from the load is via neutral to your panel (assuming one), not the ground.
pskaudio
No user serviceable parts inside me...
Okay, so these were not US market pieces. If you haven't had ground loop hum or other problems and wire internally as it's supposed to be, you're fine.
that is true, the return current path, within the house and ONLY within the house is via the white wire.
however at the panel, or in cases of mobile home at the pole, neutral and ground are tied. in fact, there is no concept of neutral w.r.t you house UNTIL you get to the 220v step down at your pole or a pole close to the house. take a set of binocs or a rifle scope (with no rifle so people dont call the cops saying you are shooting transformers) and trace out from the safety of the ground, the wires. note, that the derived neutral and the earthing system is well tied together
the age of our grid components is 'n' in the US so its hard to state with certainty WHAT you have arriving at your house, but as it gets replaced, hot, of various phases and/or voltages is sent on the crossbars and the earth-copy is sent on the insulator just below that. At my house in the woods, I have exactly 2 wires, the upper hot at >1kv and ground. at every pole, the ground is repeated AND run to earth with at least a #4 conductor and in most cases the guy wire. locally, YMMV
JP
7480 74111110101115
...and the C.T. is connected where the main filter capacitors are grounded... wait, we are talking about power transformers in amplifiers, right?
No, this side-bar is in regard to service entrance to my residence.
Yes, but in this case it's the service-side neutral. I may be butchering terms here.
I LIKE MUSIC
Super Member
Back on the farm, we always argued about 2 prong versus 3 prong.
The frog legs tasted good either way...
The frog legs tasted good either way...