Hot / Neutral reversed on outlet

[Mick Bailey]

There's plenty of domestic equipment in the UK with 'figure of 8' type IEC connections which can be inserted either way, but I can't say if there's a European equivalent of the wall wart I mentioned or whether it's constructed differently to account for non-polarized countries. Quite a lot of equipment has the modern-day equivalent of death caps, but it comes down to the class of cap that's used.

[Chuck H]

Lots of older gear had "polarity" switches and what we call death caps. That doesn't mean it's a good idea. Well, it was for getting quietest operation on the fly under less regular conditions. But certainly with higher danger risks relative to that "isolation" Juan was talking about. And lots of things can go wrong. There's a reason changes were made to grounded, polarity specific AC plugs. Of the nine posters on this thread three have reported experiences where something went dangerously wrong because of polarity and ground issues with AC outlets. I'm sure such stories are still happening in places where polarity and grounding haven't been standardized. We just don't hear much about it because it's common, and/or electronics regulations in those regions stipulate greater isolation in electronic designs. It can't be for any other reasons because, of course, electricity has no idea what country it's in.

[nevetslab]

Lots of older gear had "polarity" switches and what we call death caps. That doesn't mean it's a good idea. Well, it was for getting quietest operation on the fly under less regular conditions. But certainly with higher danger risks relative to that "isolation" Juan was talking about. And lots of things can go wrong. There's a reason changes were made to grounded, polarity specific AC plugs. Of the nine posters on this thread three have reported experiences where something went dangerously wrong because of polarity and ground issues with AC outlets. I'm sure such stories are still happening in places where polarity and grounding haven't been standardized. We just don't hear much about it because it's common, and/or electronics regulations in those regions stipulate greater isolation in electronic designs. It can't be for any other reasons because, of course, electricity has no idea what country it's in.

I've always been puzzled by a generation of Fender amps having a 3-wire grounded AC Mains cord, WITH the 3-position Grounding Switch, coupled to the Death Cap. I think I've eliminated all of those from our inventory, but, there may be some still lurking about, with so many of them not going out on rentals that often. I know I've nailed all of the Twin Reverbs and Deluxe Reverbs, though they did that on so many models in that era.

[Leo_Gnardo]

I've always been puzzled by a generation of Fender amps having a 3-wire grounded AC Mains cord, WITH the 3-position Grounding Switch, coupled to the Death Cap. I think I've eliminated all of those from our inventory, but, there may be some still lurking about, with so many of them not going out on rentals that often. I know I've nailed all of the Twin Reverbs and Deluxe Reverbs, though they did that on so many models in that era.

I think engineers call that the "belt and suspenders" approach. If you want the old fashioned Fender shock hazard, just stick on a 3-to-2 prong adapter - or tear off the ground pin with pliers - then flick the switch until sparks fly. For that authentic Fender feeling! BZZZZZZZT ! ! ! It's not a rock show until somebody gets shocked at least once.

[g1]

I've always been puzzled by a generation of Fender amps having a 3-wire grounded AC Mains cord, WITH the 3-position Grounding Switch, coupled to the Death Cap. I think I've eliminated all of those from our inventory, but, there may be some still lurking about, with so many of them not going out on rentals that often. I know I've nailed all of the Twin Reverbs and Deluxe Reverbs, though they did that on so many models in that era.

You'll find a lot of current production gear with caps across the AC line. Whether switched or not is kind of moot.
To try and eliminate them all would be a never ending battle.
The caps are there for a reason, and the modern ones are a type considered safe and acceptable. (look at switch mode supplies and line filters)

I think if we get rid of the troublesome (non-safety rated) ones in vintage gear, and install 3 prong if not present, then we have done our part.

[J M Fahey]

Typical death cap rating was 600V DC

Hey!!!! mains is 115/117V !!! (way back then) ... I have a HUGE safety margin!!!

Think again.

To begin with, that mains voltage means 150V peak.

And that IF everything is as in the textbook ... but let lightning hit a transmission line, even hundreds of miles away, and all Hell breaks loose.

Yes, there are spark gaps to deal with that ... but they trigger with scary high voltages ... or they would trigger all the time.

I checked "250 VAC" caps meant for line filtering duty , just quoting from memory they had to stand 3000V DC for 1 hour and 5000V DC for 1 minute, or similar specs.
Or 2000 and 3000 ; in any case the point being that old standard 600V DC is absolutely inadequate by modern standards.

Didn´t check X and Y rated caps, but I bet they at least meet or surpass these specs, adding fail safe failure modes.

[olddawg]

I play a lot of venues, but mostly dive bars nowadays. I always ASSUME that ALL outlets are suspect. A brand new recepticale in an old building means nothing. Usually I will run the whole band with a breakout box off of one outlet so everything at least has the same reference and hope for a sturdy breaker. I ALWAYS use a wireless.... only a total cork sniffer will say they can tell a huge difference live. The absolute worst is an outdoor gig with generators. I loath to even plug in. I played a big gig in LV a couple of years ago, I saw the whole back line fried TWICE in one day. Luckily it was all rented by the event. 2 JCM800s, a JCM900, 2 vintage SVTs, and a bunch of other stuff fried.

[SoulFetish]

I play a lot of venues, but mostly dive bars nowadays. I always ASSUME that ALL outlets are suspect. A brand new recepticale in an old building means nothing. Usually I will run the whole band with a breakout box off of one outlet so everything at least has the same reference and hope for a sturdy breaker. I ALWAYS use a wireless.... only a total cork sniffer will say they can tell a huge difference live. The absolute worst is an outdoor gig with generators. I loath to even plug in. I played a big gig in LV a couple of years ago, I saw the whole back line fried TWICE in one day. Luckily it was all rented by the event. 2 JCM800s, a JCM900, 2 vintage SVTs, and a bunch of other stuff fried.

The guitar player in the last band I ran sound for recently used a wireless setup. The particular unit he used was pretty noisy on this night. But, I've used some wireless systems in playing a couple of large auditoriums and outdoor venues, and if you factor in all the acoustic effects from the physical distance between the mains sound reflections, monitor sound, and location of the amp, I don't know if I could tell any difference at all between a RF and direct cable connection. If there was a "live chassis" fault situation, there is still risk of physical contact with the amp, through an effects loop or controls adjustment. But, it does offer a really attractive margin of safety.

[Chuck H]

The guitar player in the last band I ran sound for recently used a wireless setup. The particular unit he used was pretty noisy on this night. But, I've used some wireless systems in playing a couple of large auditoriums and outdoor venues, and if you factor in all the acoustic effects from the physical distance between the mains sound reflections, monitor sound, and location of the amp, I don't know if I could tell any difference at all between a RF and direct cable connection. If there was a "live chassis" fault situation, there is still risk of physical contact with the amp, through an effects loop or controls adjustment. But, it does offer a really attractive margin of safety.

The only time I took a hit was when holding my (cable connected) guitar and touching the mic. Which raises the question... Why the hell is the average mic screen grounded to the case?!? Anyway, yes a wireless does provide a good safety margin. Believe it or not I was always careful not to touch potentially grounded or hot parts on other systems whenever hooking things up for gigs. But that was setting up. Put a guitar in my hands and a mic in front of me and it changes because I'm trying to perform an art, not execute a logical function. So my lips touched the mic screen and I got knocked to my knees. It started with HUMMMMMMM!!! And then arms slack and guitar feeding back acoustically while I tried to reconcile if I was actually hurt. We took a break and finished the show

[J M Fahey]

Why the hell is the average mic screen grounded to the case?!?

Shielding.

[nickb]

Shielding.

Since the shielding is for the electric field I would have thought a suitably rated low inductance capacitor no bigger than 10nf ( approx 1mA at 240V 60Hz) instead of the wire to the case would be almost as effective and would eliminate the possibility of electrocution by touching the mic case. The inductance of the leads would have to be kept as low as possible so think really short.

[Leo_Gnardo]

Since the shielding is for the electric field I would have thought a suitably rated low inductance capacitor no bigger than 10nf ( approx 1mA at 240V 60Hz) instead of the wire to the case would be almost as effective and would eliminate the possibility of electrocution by touching the mic case. The inductance of the leads would have to be kept as low as possible so think really short.

Still... enough of a shock for a person to feel, especially on the lips.

I remember a couple decades ago, local farmers were complaining after a new 745 kV power line was installed, their cows would not eat grass on fields under the line. There was enough of a field to deliver a mild buzz but that's all it took to set 'em off. The shock was enough to "train" the cows to avoid grass on other fields too. How to convince 'em "it's OK Bossy, no shock here..." Same goes for some vocalists - once you catch a good buzzer it's hard to approach the mic again. Put a big foam "sock" on it !?!

[Chuck H]

My thinking was that since "touching the mic" has been a common denominator in the problem often enough that (maybe) some clever manufacturer could have started coating the screen with insulative material or use a secondary plastic guard or some such. I hate spit guards, but I use them. I bought a big, fat bag of them after my shock and changed them every so often when they got smelly or whenever someone of questionable oral hygiene used my mic

[glebert]

use a secondary plastic guard or some such.

Is the metal screen on an SM57 actually grounded? I had a friend in college (where all the houses and bars had terrible wiring) who would only sing with 57's because he got shocked less than 58 style mics.

[Leo_Gnardo]

Is the metal screen on an SM57 actually grounded? I had a friend in college (where all the houses and bars had terrible wiring) who would only sing with 57's because he got shocked less than 58 style mics.

Having dissected several SM57's, the screen is not grounded but held in a groove in the plastic end cap. Same for the similar PE54 series that look like silver body SM57's. Likely the same for the rarely seen SM77. Can't speak for SM57B or any other variant.

Yes those college facilities had some very dodgy situations. I remember playing gigs in the basement of an off campus fraternity, crammed into a corner of the room with a steel lolly column in the middle of the stage. Touching the lolly pretty well guaranteed a painful shock no matter where one's "ground" switch was set. Of course that was back in the day when grounded AC outlets were rare, same for grounded AC cables on amps. BZZZZZT - - -OW OW OW !!!