Do they make polarity reversing plugs or cords?


Old 02-12-14, 09:00 AM
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Do they make polarity reversing plugs or cords?

I am using a Mr DJ PSC400 to provide separately switched powered for a number of attached items. I noticed that a UPS plugged into it indicated a wiring fault. I know the outlet is fine, and when I connected the UPS directly to an outlet to test it didn't indicate the fault. A little googling found a review on Amazon that stated that the similar PSC200 reversed hot and neutral.

Rather than try to take apart the PSC400 and fix the issue, if I could find a "cheater plug" that reverses polarity instead of not connecting ground I could fix the issue.

Has anyone ever heard of such a thing? It seems like one of those things someone has to make, but figuring out what exactly it would be called would be the key to finding it. Googling "polarity reversing plug" just gets me a lot of content having to do with people finding hot/neutral is swapped in their outlets and how to correct it.
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Old 02-12-14, 10:50 AM
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You've had a lot of trouble finding what you're looking for because no one makes them. It would be a band-aid to fix something that's already not wired correctly.

If all you're running are incandescent lights, the hot/neutral swap shouldn't matter.

You could make your own 'cheater cord' with a cord and plug, but it seems to me like it's a lot of patch work. Or get one that sounds like it's better made and hopefully UL listed. I can't imagine this one is.
Old 02-12-14, 10:50 AM
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Return it.

Call the company and tell them what you've found. Is it UL listed? It doesn't sound like it.

A "cheater" plug would not be to code.
Old 02-13-14, 06:15 AM
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It would be easier and faster to just open it up and swap the wires if it was wired backwards. It's just a cheepo plug strip with no other circuitry.
Old 02-13-14, 07:39 AM
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VERY strange that a power strip marketed for use with stage equipment would have hot & neutral reversed. With all the different devices & varied power sources found on a typical stage an error like that can get someone killed.
Just sayin...
Old 02-13-14, 08:19 AM
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And the proposed adapter could get someone killed so it should not be made.
Old 02-18-14, 02:44 AM
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I powered everything down and opened it up hoping to reverse the polarity inside it, but everything is soldered. I don't own a soldering iron or know how to use one even if I did. So unless I can find the type of plug I'm looking for I guess I'm out of luck for making this thing work properly.

I realize it "shouldn't be made" because it is unsafe if used improperly, but the same is true of ground lifting cheater plugs, and those are easy to find. I'm still hopeful that someone, somewhere, probably makes a polarity reversing plug or cord, but whether I will ever find it is another matter I guess.
Old 04-13-14, 08:01 PM
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Still problems with reversed polarity in PSC400

So I found a solution a few weeks after my last post. Since the PSC400 is just a switched outlet strip, and I wanted some surge protection, I fed it using a Furman AC-215 power conditioner. That has two outlets in it, and a single switch. I opened it up and it uses spade connectors so I was able to reverse hot/neutral on one outlet (and clearly marked that outlet just in case, even though I'm the only one who will ever touch this stuff)

So that fixed the problem with hot/neutral being reversed, or so it seemed. I recently noticed there is still something strange going on. One of the devices plugged in it is a 24v regulated power supply, which supplies power via RG6 coaxial cable to a device that has LEDs on it. When the switch on the PSC400 is "off", every couple minutes the lights on that device flicker for a split second. I tried plugging it in directly to the AC-215 and it doesn't flicker then, so it is clearly the PSC400 that is responsible. I tried another outlet on the PSC400 with the same result, so if one switch is defective, they all are.

I have a theory why, tell me if this is reasonable. If the PSC400 disconnects hot but not neutral when "off", then neutral is still connected to the power supply. The power supply's DC output is grounded through a coaxial cable. So if the power supply has ground on the DC output and a "live" neutral on the input, if there's a very slight potential difference between that neutral and that ground, maybe that's enough to power the caps and allow a tiny burst of energy sufficient to flicker the LEDs on the attached device every few minutes.

Does this sound like a reasonable explanation? If so, is this something I should be concerned about? The things plugged into the PSC400 are on 99.9% of the time so having an off that allows a tiny trickle charge isn't a huge problem, unless someone who knows more than I do tells me that it is Or maybe someone has an alternative explanation for what is going on?
Old 04-13-14, 09:56 PM
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I read this thread with a little bit of.......... concern. I would have returned that power strip in the blink of an eye or repaired it properly.

Since now you are switching the neutral instead of the hot you may see odd things happen.

I've seen too many musicians shocked by issues like this.
What you are doing is dangerous and should not even be up for discussion.
Old 04-14-14, 06:57 AM
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Ideally you should return it to the store or vendor as having a manufacturing defect.

Always a good idea -- Daisy chain a ground wire (suggest #14 or #12) among all the pieces of equipment that do not have 3 prong power plugs. Connect the far end to a known ground, in most cases the screw holding the cover on an exposed metal outlet box with exposed rigid metal conduit will do on a theater stage. If you have reason to believe that the 3 prong receptacles are not properly grounded, then run the ground wire to all equipment. The wire would be connected to the chassis or to the outer shell of one of the input or output jacks. This grounding procedure greatly reduces hum and noise and also greatly reduces shock hazards.
Old 04-14-14, 08:18 AM
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I'd get rid of that thing if I was you. This seems like a China special, and considering the price, I'd place it with all of the other "Budget" DJ gear. I've opened up a power strip rated "20A 125V" and found the insides to be wired with #18. You're best sticking with your Furman, or getting something from another reputable brand such as APC, Tripp Lite, Monster Power, etc. I personally use a Tripp Lite RS121520 for my gear.
Old 04-14-14, 08:58 AM
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Just cut the plug of MR DJ and put on one like this:

Old 04-14-14, 11:47 AM
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It turns out it is pretty hard to find a rack mountable outlet strip with individually switched outlets. I needed an easy way to power cycle individual items but not all of them. The suggested Tripp Lite product would not do what I require as it has only one switch for all outlets. I found a few other similar products, but checking them later none seem to be UL listed. Its too late to return it now, but even if I did the alternatives may be no better. They're probably all "China specials".

Just to alleviate some concern, this is used in an equipment rack for A/V and networking gear that's in a fixed spot and I'm the only one who touches it. The internal wiring looked to be 12 or 14 gauge, and the total load is under 10A, so overload isn't a concern. The only items with grounded plugs plugged into it are a UPS (but nothing plugged into it is grounded) and an outlet strip for audio gear, which has a grounded amp plugged into it, and the rest is ungrounded. So aside from the UPS and the amp, everything else uses a 2 prong plug and has an internal switching power supply.

I thought that switches were supposed to be switching both hot and neutral, but if this switched hot only I can see where that would be a problem as I'd now be switching neutral only. Since these devices are on 24x7x365, other than when I power down briefly to make changes (and I'll be sure to unplug the PSC400 when I do so, rather than relying on turning off its individual switches) or turning something on/off to power cycle it, I figure that's probably not a major concern. I'm the only one who would ever risk being shocked, and now that I know there's a chance hot may be unswitched I'll know to be extra careful!

I could put it back how it was with hot/neutral reversed, but I was and still would be concerned that reversed hot/neutral would be bad for the UPS or audio amp over time. Should I be worried about that? Everything else runs off a switching power supply, I believe those work the same with hot/neutral reversed.
Old 04-14-14, 12:08 PM
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I'd be more worried about someone touching the mic with a sweaty hand and getting electrocuted... Especially when the investigation discovers your hack job and you end up on the hook for reckless endangerment...

I do theater tech as a hobby and believe me there are plenty of liability considerations when you MacGyver something that 'only you will touch'. Because you can't guarantee that.
Old 04-14-14, 08:24 PM
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Like I said, this is not something that anyone else will touch. There is no "mic", this isn't a DJ or sound system setup. I used a MrDJ product only because DJ gear seems to be the only one where the need of having individually switched outlets seems to have been filled, but this is powering an AV rack in a closet.
Old 04-14-14, 09:02 PM
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I still wouldn't want to risk that. Why do you need some receptacles switched in the first place?

The only items with grounded plugs plugged into it are a UPS (but nothing plugged into it is grounded) and an outlet strip for audio gear
That is also against code, power strips, UPS units, etc. must be connected directly to the wall.

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