Old Gibson Amp Question

LuthierVandross

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I picked up an old 70’s G-55 amp a few years back and just now getting to mess with it.

it doesn’t have a grounded power chord, is this going to be an issue?

I plan on plugging into a surge protector, but one can never be so careful.
 

ARandall

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Its never an issue.....until suddenly it is.

The thing is with electricity, you make a mistake and you are actually running the serious risk of death. And unlike power tools where you can see or feel when something is about to go wrong, you'll never know quite when the line is crossed with power.
 

LeftyF2003

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While they're in there you might want to check the caps as they tend to drift in value over time.
 

LuthierVandross

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Its never an issue.....until suddenly it is.

The thing is with electricity, you make a mistake and you are actually running the serious risk of death. And unlike power tools where you can see or feel when something is about to go wrong, you'll never know quite when the line is crossed with power.
You mean if I play this amp without the third ground prong, I run the rush of electrocuting myself?
 

Gridlock

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Keep the 2-prong only if you like getting zapped.

I have made sure that the old two-prong plug was changed out to a three-prong grounded plug on every vintage amp that I’ve owned. If you plan to use the amp, I believe that this is a mandatory upgrade.
 

strayedstrater

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You mean if I play this amp without the third ground prong, I run the rush of electrocuting myself?
Yes.

I started playing in '72, just as 3-prong polarized plugs were being introduced. Many places I played still had 2-prong outlets so I always carried a 3 to 2 prong adapter with me.

Not many people actually died (though some did). But just about everyone experienced shocks, ranging from mild tingles to "ow, that hurt like hell". We learned how the shocks happened, and did our best to avoid them.

The strings on your guitar are grounded, to reduce noise. But with 2 prong plugs, if you plug into the wall one way the strings are grounded, but plug in the other way the strings are hot. If the strings are hot, you don't feel it and it doesn't cause any problems -- unless you touch something that's grounded. Then electricity flows from the strings through your body to ground.

Barefoot on a concrete floor, lips touching a microphone, touching another player or their amp, touching a piece of recording equipment, anything conductive that's grounded = zap. Pain is a good teacher and we quickly learned not to do those things.

But it's easy to slip up. And most people have grown up in a 3-prong polarized world where shocks are super rare, so they've never learned that conductive things might try to kill them.
----------------
If you use that amp before getting the power cord replaced, let go of the strings (and other metal parts) before you touch anything that may be conductive.
 
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LuthierVandross

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Can I plug the amp into a surge protector strip to avoid this? I don’t even know if I want to keep this thing, but I’d like play it to find out
 

ErictheRed

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Can I plug the amp into a surge protector strip to avoid this? I don’t even know if I want to keep this thing, but I’d like play it to find out
No, that won't help. You just want to have a 3-pronged cord properly installed. Trust me, I'm an electrical engineer.

Having said that, if you want to turn it on at home by yourself there is almost no risk. The danger really happens when there's something else around, like a microphone or another guitar amp, that is out of phase with yours. So fire it up by itself away from other electronics and you'll be fine. You might destroy the amp if the filter caps are bad, however, so if you have no idea what's going on and it hasn't been turned on for decades, I might bring it in to an amp tech.
 
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sll

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You definitely want, need, a properly installed grounded power cord. The black conductor should go to the fuse first, then the power switch, and then the power transformer. The green, ground, conductor should be the longest of the 3 so that if the power cord is pulled out the ground remains connected the longest.
 

strayedstrater

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If your kitchen or bathroom has GFCI outlets (the ones with test/reset buttons), you'd get a measure of extra safety plugging into one of those. (You can use an extension cord if you don't want to play in the kitchen or bathroom.)

Some power strips have reset buttons. Those aren't the same thing. Those only trip during a major power surge (after you feel the shock). GFCI outlets trigger with only a tiny leakage of hot to ground and will shut off the power before you even feel the shock.

But as ErictheRed said, trying it out at home is pretty safe as long as you don't touch any other electrical equipment.
 

morelespauls

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Its never an issue.....until suddenly it is.

The thing is with electricity, you make a mistake and you are actually running the serious risk of death. And unlike power tools where you can see or feel when something is about to go wrong, you'll never know quite when the line is crossed with power.
Its never an issue.....until suddenly it is.

The thing is with electricity, you make a mistake and you are actually running the serious risk of death. And unlike power tools where you can see or feel when something is about to go wrong, you'll never know quite when the line is crossed with power.
Yeah, a car wreck is never a issue till it is.:fingersx:
 

pmonk

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The only non-grounded piece of equipment I own is an Premier 90 Reverberation Reverb Head.

Works great but I avoid touching it at all cost
 

ehb

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A three prong mod is hella cheaper than getting an appropriate Iso Xfmr...

Just do it... Talk t an old fart that has been bitchslapped by a mic.... or you could stick a stun gun in your mouth....

All it takes is once.....
 

LuthierVandross

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Yeah. I’m kind of leaning of disposing of the amp. Sounds like a death trap I don’t want to get involved with, or pass onto some one to get hurt.
 

redking

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Most of my amps are from the 60's and early 70's - every single one I bought in the last 10 years. First thing I do is take it to my amp tech for a check-up and add a 3 pronged cord. I have had no problems with any of my vintage tube amps doing it this way.

That being said - a Gibson G-55 is a solid state amp - so correct me if I am wrong amp techs - the OP shouldn't really have to worry about lethal doses of high voltage in a SS amp? I think adding the 3 prong chord in this case will simply make it run quieter. It's basically like a transistor radio.
 

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