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Author Topic: NCV testing positive on IEC cables  (Read 2030 times)

dave briar

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Re: NCV testing positive on IEC cables
« Reply #10 on: April 10, 2020, 03:00:52 pm »

Being reverse wired usually isn't a problem. An AC load doesn't care which line is hot and which is neutral

If the power cord is directly supplying a power switch that only interrupts the "hot" line, leaving the neutral connected, or if it somehow references chassis ground to neutral, or if it has a circuit breaker or fuse that interrupts only one line, then reverse wired could be a problem. If the switch or circuit breaker interrupts both lines, a reverse-wired cord isn't unsafe.
Right, and to whit, the five monitors all worked fine for a few years until one day one didn’t. Just went inert. My “helper” at the time went to the stage and upon disconnecting the power cord (terminated with a True1 connector) noticed that the connector was loose on the cable and so twisted it almost 180 degrees to demonstrate it to me — while it was still plugged in no less.  Sparks and a blown breaker were the result. It was while replacing the True1 connector that I discovered the reversed hot and neutral. I asked the FBT repair guy whether based on his knowledge of the internals of the monitor that might have been in any way related to the monitor dying.  He didn’t think so right off but would take a closer look and let me know. Nope was his reply an hour later, just a coincidence that both issues occurred on the same monitor. Still, I rewired the two other cables so that the hot wire connected to the “L”ine terminal on the True1. All five monitors are still working fine.
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Daniel Levi

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Re: NCV testing positive on IEC cables
« Reply #11 on: April 10, 2020, 03:18:06 pm »

Being reverse wired usually isn't a problem. An AC load doesn't care which line is hot and which is neutral

If the power cord is directly supplying a power switch that only interrupts the "hot" line, leaving the neutral connected, or if it somehow references chassis ground to neutral, or if it has a circuit breaker or fuse that interrupts only one line, then reverse wired could be a problem. If the switch or circuit breaker interrupts both lines, a reverse-wired cord isn't unsafe.

And, of course, in Europe Schuko, Italian or un-earthed 2 pin plugs will go in either way, it's only earthed French/Danish/Swiss/UK plugs that are polarised (although I believe originally France had no standard as regards to polarity), plus anything with a "figure-8" connector will also have random polarisation.
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Robert Lofgren

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Re: NCV testing positive on IEC cables
« Reply #12 on: April 11, 2020, 10:01:45 am »

Here is an interesting video explaining why leds glows even when turned off. It is kind of related to this issue...

https://www.youtube.com/watch?v=jqTOrSDFVg0
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Ivan Beaver

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Re: NCV testing positive on IEC cables
« Reply #13 on: April 15, 2020, 03:40:56 pm »

Being reverse wired usually isn't a problem. An AC load doesn't care which line is hot and which is neutral

If the power cord is directly supplying a power switch that only interrupts the "hot" line, leaving the neutral connected, or if it somehow references chassis ground to neutral, or if it has a circuit breaker or fuse that interrupts only one line, then reverse wired could be a problem. If the switch or circuit breaker interrupts both lines, a reverse-wired cord isn't unsafe.
Yes, the gear may "work" fine, but does it sound fine? with the polarity of the AC line reversed?

Just ask any true hifi guy who can "hear" when the power company changes the polarity of the AC.  It makes their systems unlistenable.  So they have to wait until the power company flips the polarity back to the "correct" position in order to listen to their music.

NO, I do NOT make this stuff up-----------------------
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
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PHYSICS- NOT FADS!

Jonathan Johnson

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Re: NCV testing positive on IEC cables
« Reply #14 on: April 15, 2020, 05:34:01 pm »

Yes, the gear may "work" fine, but does it sound fine? with the polarity of the AC line reversed?

Just ask any true hifi guy who can "hear" when the power company changes the polarity of the AC.  It makes their systems unlistenable.  So they have to wait until the power company flips the polarity back to the "correct" position in order to listen to their music.

NO, I do NOT make this stuff up-----------------------

Do they use audiophile batteries in their IR remote controllers, too?
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Ivan Beaver

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Re: NCV testing positive on IEC cables
« Reply #15 on: April 15, 2020, 08:44:10 pm »

Do they use audiophile batteries in their IR remote controllers, too?
Nothing digital for those guys.  Pure analog baby!!!!!!!

The fewer the controls the better.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

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Jonathan Johnson

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Re: NCV testing positive on IEC cables
« Reply #16 on: April 15, 2020, 08:56:06 pm »

Nothing digital for those guys.  Pure analog baby!!!!!!!

The fewer the controls the better.

So you're saying they'd cut off their fingers to spite their ears?
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Kemper Watson

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Re: NCV testing positive on IEC cables
« Reply #17 on: May 02, 2020, 10:30:59 am »

Yes, the gear may "work" fine, but does it sound fine? with the polarity of the AC line reversed?

Just ask any true hifi guy who can "hear" when the power company changes the polarity of the AC.  It makes their systems unlistenable.  So they have to wait until the power company flips the polarity back to the "correct" position in order to listen to their music.

NO, I do NOT make this stuff up-----------------------

 How and why I knew it was reversed? Every time I plugged into the drop snakes with the PA muted there was a small pop. Less than phantom power but enough to know something wasn't right. DMX was run down snake lines. When I unplugged the DMX lines popping quit. I have these plugs that glow red when the hot/ neutral is reverse. I used this to chase down the issue . Once the reversed cable was found and removed the popping quit.
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John Roberts {JR}

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Re: NCV testing positive on IEC cables
« Reply #18 on: May 02, 2020, 11:54:09 am »

Yes, the gear may "work" fine, but does it sound fine? with the polarity of the AC line reversed?

Just ask any true hifi guy who can "hear" when the power company changes the polarity of the AC.  It makes their systems unlistenable.  So they have to wait until the power company flips the polarity back to the "correct" position in order to listen to their music.

NO, I do NOT make this stuff up-----------------------
some semi-pro (code for not pro) 2 wire line cord gear, grabs a psuedo ground from the nuetral (that should be 0V and grounded at the service drop).

These not pro SKUs sometimes capacitor couple neutral to chassis ground to provide some shielding. Of course reversed line and neutral is now dumping AC current into the chassis shield. These caps are sized to avoid creating a safety hazard, but can corrupt audio integrity.

I have encountered audio issues last century trying to pass audio through prosumer/semi-pro gear using two wire line cords.

JR
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Re: NCV testing positive on IEC cables
« Reply #18 on: May 02, 2020, 11:54:09 am »


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