Lifting the ground an a Marshall amp

[ggunn]

Yup. It sucked, but still didn't kill me.

Well, of course not. Otherwise, anyone who could have answered "yes" to the question couldn't have answered at all, right? I was just looking for others who share that experience, which is kinda like getting hit simultaneously in the hand and in the nuts with ball peen hammers. I feel your pain.

 

[dementedchord]

i can kill ya with 12V but i can torure ya with 1200... ummhh boy that can hurt... i got thrown across the room once when i grabbed a 600V line in an old hammond.... it was outta the cabinett and as a smoothing filter they used a separate coil in the speaker (which also provided the magnetism... the speaker was not a permanant mag.. way wierd...) anyhow i had to "jumper" it and it bit me....

 

[ggunn]

i can kill ya with 12V but i can torure ya with 1200... ummhh boy that can hurt... i got thrown across the room once when i grabbed a 600V line in an old hammond.... it was outta the cabinett and as a smoothing filter they used a separate coil in the speaker (which also provided the magnetism... the speaker was not a permanant mag.. way wierd...) anyhow i had to "jumper" it and it bit me....

Field coil speaker. Most jukeboxes have them, or used to. They are very efficient, but need high voltage power supplies to run them. I knew an old guy back home who built bass guitar baffles with field coil speakers many years ago.

 

[Adam P]

It's not a ground lift, it's a (not) clever little thing which also goes by the colorful name of "the death switch." If I were you, I'd take it to a good amp tech and have them disable it for you, because they really are a bad idea. Basically, what they do is to switch a cap-to-ground between the hot and neutral legs of the incoming Mains. The big problem with them is that, when the cap shorts (as they eventually do), if it is switched to the "hot" side it will send 120v at basically an infinite current to the chassis until it trips the breaker. If you don't have the amp grounded, or if you (through your guitar cable) are a better path to ground, then you may as well have stuck a key in the wall socket, because that is what is going through YOU.

Bad Juju, all around.

By the by, if it is blowing your breaker, it almost certainly means that cap IS blown. That being the case, I need to revise my advice; RUN to the nearest qualified tube amp tech and have them yank that fucker out of there before you turn the amp on again. It may be the cap is just leaky, and your not in danger of getting the full Don King hair treatment, but better safe than sorry, you know?

Seriously, those things EARNED the name "death switch."


Light

"Cowards can never be moral."
M.K. Gandhi

Many thanks. I'll get right on that.

 

[MCI2424]

As little as 18 milliamps can be fatal under the right conditions.

That's 18/1000's of a SINGLE AMP.

And the higher the voltage delivering the current the more likely it can overcome the resistence of your skin.

What matters is the path the current takes. Many, many more people get shocked through some part of their body, but a fatal shock is directly through the heart. That is what does you in. Never grab anything electrical with both hands. #1 rule in electrical/electronics. TV guys always have 1 hand in their pocket when working on CRT parts.

 

[c7sus]

Actually you don't need to pass current from hand-to-hand in order to stop your heart.

The worst hit I ever got was the neutral on a 277v flourescent lighting load. I was stripping the neutral that was carrying the entire load and grounded my elbow or upper arm against the ceiling grid-- which is always grounded BTW--- and then got knocked off an 8-foot ladder in a room full of civilians.

Yeah, it was a dumb thing to do but when you're young and in a hurry you do crazy things.

It's also becoming a lot more common to send guys to the hospital for overnight obsevation following even simple cases of getting bit because it's been shown you are more susceptable to heart attack following even small jolts.