shocked by 1960s amps when playing in rainy weather- what caused it? what to do about it?

naneek

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as we know, in the 60s and 70s musicians used to get shocked by their amplifiers and pa systems. for example, this is documented in the "Get Back" Beatles documentary in episode one. one of the mics was shocking them, and even though they are playing indoors, Paul says it happened because it's raining. (woodstock is another extreme example. The point is it was commonplace.)

What caused this? Have any of you had these problems with your vintage amps?

I have a really sweet early 60s gretsch dual twin which did this. I haven't used the amp in years because it needed basic maintenance and I didn't want to take any risks with it. It had maintenance in the late 80s, performed fine for 20 years, and then I stored it.

One time when it was rainy, I felt very mild intermittent shock through my strings. It was subtle. once I noticed it, I shut the amp off. I stored it a few months later until I could get maintenance done.

what do you think caused the shock?
(the amplifier used to belong to my dad, he said "it just does that.")
what if anything did that mild shock mean for my amplifier? would that cause lasting damage?

hypothetically, what could have happened if it had been a more substantial shock?

Fast forward ten years, I finally found a good amp repair shop. I am about to pull the old gretsch out for some maintenance.

Out of an abundance of caution, I'm going to tell the amp repair tech to assume it is broken and potentially dangerous. even though the shock I received was very mild, that was years ago so I am not going to make any assumptions.

can you think of anything else I should mention to the repair tech?
 

Peegoo

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It's caused by an amp having a non-polarized, ungrounded mains plug.

This is why many older 2-wire non-grounded electronics had a polarity ("ground reversal") switch: you flip the polarity on the device to help prevent shocks.

Compounding matters is having two electrical devices that are ungrounded, with mismatched polarity. For instance, a guitar plugged into an amp, and a microphone plugged into a PA. If the guitar amp and PA mixer are not polarity matched, holding a guitar and touching the mic (with your lips!) could deliver a jolt at mains voltage. People have been killed by this stuff.

Technically, AC has no actual polarity but the neutral leg of an AC circuit is tied to the ground buss at the breaker panel. So in a sense--polarity in an AC circuit does matter.
 

metalicaster

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It can be the building wiring with differing resistance to ground, not necessarily an ungrounded amp.

It was certainly a problem with old British amps, and we had grounded plugs on them all since before the war. Then again, 240 tingles a bit more…
 

The Ballzz

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Older Ampegs are also notorious for this, along with some models having circuitry that when certain components fail, they present voltage to the chassis and your guitar, because the guitar is grounded to that chassis. There's also a thing in many amps that is referred as a DEATH cap, with good reason, when it fails! :eek:
Just My $.02,
Gene
 

summer_69

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In the late 70 it became obligatory with a RCCB in electrical installations. That and grounding availablie in power outlets have saved a few lives. If ground is not present in the power outlet/cord then there is on older equipment (always) a grounding point (a screw with a knurled brass nut) indicated with a grounding symbol. Often also mentioned in the manual btw ;)
 

Red Ryder

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Any idiot knows that playing an electric guitar in a jacuzzi or a hair dryer in a shower is dangerous. However appliances such as a toaster, electric razor or clock radio are perfectly safe as long as you are standing on a bucket with a secured grounding rope around your neck.
 

Old Deaf Roadie

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There was once a club located in a locally historic building we would provide audio services for that had more than just a couple of wall sockets that were wired with hot to neutral. That stage, coupled with ungrounded amps was 100% why we used foam windscreens on the vocal mics when we worked there.
 

maxvintage

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I had a gig once at a local place, an outdoor gig, and it started to rain. I looked at the leaky stage and the way they had the stage wired--frayed extension cords wrapped in some places with duct tape--and said "Sorry guys not playing this gig in the rain." The band looked at what I was seeing and agreed.
 

radtz

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I remember one outdoor gig with a grounding issue. Every time my lips would touch the mic I would get the equivalent of a static shock. That was a miserable time. Unlike a horse, cow or, dog I could not learn the lesson of to avoid a shock. In retrospect, I am amazed I have lived this long.
 

arlum

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I figure it's all about grounding. As good as the builds were they were still limited to the accepted tech of the era they were built in.
 

Paul G.

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Paul McCartney, a man who is responsible for some of the best, and somehow, some of the worst songs ever written is not, to my knowledge an engineer.

People accepted the results of ungrounded wiring and bad polarity because it was common.

Also: in many amps the "ground" switch did not reverse polarity, it just reversed the leg connected to the "death cap" for noise reduction. Flipping the switch didn't save you from mic shock.

So--unless you are the curator of an electronic device museum, any old amps you intend to actually use should have grounded plug installed to modern safety code.

There was once a club located in a locally historic building we would provide audio services for that had more than just a couple of wall sockets that were wired with hot to neutral. That stage, coupled with ungrounded amps was 100% why we used foam windscreens on the vocal mics when we worked there.

I keep a circuit tester in my bag. If something seems wrong, I use it to check all outlets. Any bad ones are taped over with painter's tape to keep people from plugging in. If they're all bad, I go home.
 

zook

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The problem is reversed polarity with 2 prong cords. We used to check to see if we got shocked by quickly touching the mike or mike stand to see it they were together, If they weren't we either flipped the plug in the socket or hit the ground switch.
 

Fiesta Red

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Yeah, ungrounded equipment can be a real problem…just ask Keith Relf.

If you know that a piece of equipment has problems and you keep using it, well…that’s just nature’s way of taking you out of the gene pool.

I do a similar inspection as @Paul G. ; in one particular case, I did this weeks before I even agreed to play the gig (the building was ramshackle, at best). To my surprise, the guy immediately called an electrician and had it fixed (albeit by running new conduit and outlets on the surface of the wall, which fit the industrial aesthetic of the building)…I tested the new circuits before we unloaded our gear, and it was all good.
 




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