Theory on getting burnt up by tube amp.

[tornadosm]

What needs to be done so one will not die when working on tube amps? I am fairly new and have only replaced tubes checked pt and tube bias...I am kinda worried about getting voltage shock if I dont know more. plz advise.. thanks in advance.

[Le Basseur]

Hey,
The "one hand in the pocket" principle works like a charm!
Also,read here:
http://www.geofex.com/
Great references!
HTH!
Regards,
Le Basseur

[tornadosm]

great and thank you for the site..wealth of info

I have not found anything on" one hand in the pocket " yet...but the site does have quite a bit of info, exactly what I need. I have been to Dubrovnik, Split and Medjugorje. Wonderful people there. thanks again and peace..sm

[Richard]

"one hand in the pocket" refers to keeping one hand in your pocket when probing an amp. If you place your hand on the chassis or anything else that's grounded and your other hand or tool touches voltage, the voltage will travel through your arm, torso (including heart), and back out the other arm to ground. If the other hand is in your pocket you are a lot safer.

[Amp Kat]

Hand in pocket or not if you are touching ground or chassis and come in contact with a charged capacitor your going to get zapped. Will it kill you ? Probably not but as I said before, that shit gets old quick. I've heard it also depends on your body resistance as they say everyones is different. If yours is real low you get more current but it does depend on where you get it. After a while you learn where to touch and where not to touch but if you let your gaurd down for a second it can turn around and bite you in the arss. IMO one of the shock hazards that happens most is forgetting your amp is plugged in and turned off but accidently go across the mains. I unplug my amp after testing no matter what or, kill the variac switch.

[Jag]

When I first started working on tube amps I didn't consider a few other obvious things, I suggest the following as well.

- your workbench should ideally be wood or some other non-conductive material to isolate the work surface from ground.

- always work standing on a non-conductive surface. I have some of those hard foam excersize tiles under my bench.

- always wear rubber soled sneakers. Again, for insulation.

- never work barefoot or fresh out of the shower.

- never work standing on a bare concrete floor.

I also have the power outlets on my bench connected through a ground fault interruptor.

[mooreamps]

-augh . . . .

On thing for sure. If you have a multimeter. You can measure the voltage across the filter caps to make sure they are mostly discharged before doing any work inside the chassis.

-g

[Enzo]

I don't like the one hand rule. The way people talk about it, it makes it sound as if you are safe from shocks that way. You are not. You touch something live with a finger, and if your arm happens to brush the chassis, WHAM, you just took a large poke. Or the edge of your pinkie lays against something grounded as the other finger contacts live.

Will a shock through your hand kill you? Not likely. But it might cause you to injure yourself in the reaction.

%ent, that probably wouldn't hurt you much, but you might break your arm yanking it back from the tube.


Always be aware of where your extremities are. One-hand might be better than nothing, but it is not a guarantee of safety in the slightest.

[Le Basseur]

I don't like the one hand rule.

Me neither,Enzo!It isn't really what it looks like and it's impractical from a certain level on.That's why I put a smiley after the proposition.
But...the initial poster wrote the magic word:noobie!
Instead of the "noobish" one-hand-in-the-pocket rule,I'd add something to Jag's list of safeties:neck chain!
In many cases,a repairing/measuring job is made with the tech stood up and slightly bent over the opened chassis.If someone (like me! ) has a neck chain with a crucifix,medallion or whatever,it's highly probable that by dangling over the chassis,the chain comes in touch with something in there.It's not only a receipt for a great short but a possible source of serious injure.
The only time when this happened to me,I got a nice,deep and painful burn mark around my neck.Needless to say,this was a great drivel opportunity for some of my friends: "...hey,who's the idiot who tried to strangle you backwards?"

Regards,
Le Basseur

[Enzo]

You are quite right. I do not wear any personal jewelry, nor do I wear a wrist watch. (To you young ones who look at your cel phone to see the time, a "wrist watch" was a thing you strap on your arm and it is like a small clock.) I am married but I don't wear a ring. I wore a ring a long time ago and was working on something and pulled my hand out only to have something slip under my ring, snagging me, and I was trapped. Fortunately it was not something electrical and powered up. I don't want that to happen on an AMpeg. Dangling chains are dangerous for sure. The watch thing came about when I found myself working on video monitors. On those we face that 30kV, and we also have to reach down into crowded spaces.

So we avoid wearing things that improve the electrical connection to our bodies, and also things that might make a more attractive arc target.

[Steve Conner]

Like Enzo says, the one hand in pocket rule is not a catch-all. Neither is a ground fault interrupter: it won't protect you from shocks from the B+, because the current path for that doesn't include the sensor in the GFI. Really, you just have to be aware of the risks, know what you are doing, don't work alone, don't work when tired, drunk or on drugs, and just be lucky!

I got one of those finger-to-arm shocks that Enzo mentioned, messing around with tube circuitry when I was at high school. With one hand in my pocket! My arm stuck to the circuit and I even got some small electrical burns. It hurt so bad that I was scared to go near tubes again for several years. When I finally did try them again, you can bet I was very careful around B+!

[hasserl]

You are quite right. I do not wear any personal jewelry, nor do I wear a wrist watch. (To you young ones who look at your cel phone to see the time, a "wrist watch" was a thing you strap on your arm and it is like a small clock.) I am married but I don't wear a ring. I wore a ring a long time ago and was working on something and pulled my hand out only to have something slip under my ring, snagging me, and I was trapped. Fortunately it was not something electrical and powered up. I don't want that to happen on an AMpeg. Dangling chains are dangerous for sure. The watch thing came about when I found myself working on video monitors. On those we face that 30kV, and we also have to reach down into crowded spaces.

So we avoid wearing things that improve the electrical connection to our bodies, and also things that might make a more attractive arc target.

I use to turn wrenches on heavy earth moving equipment. A coworker of mine once had his gold wedding ring on his had, and was holding a nice Snap On wrench and working near the starter solenoid. He accidentally touched the large terminal on the solenoid that has the positive battery cable attached to it, with one end of the wrench and the frame of the machine with the other end. The current going thru the wrench also went thru his ring making a nice burn all the way around his finger. Normally doing this causes lots of sparks, but besides scaring the crap out of you the only harm done is to the expensive wrench and to the end of the solenoid terminal (the threads can get melted away). This time he got a nasty burn out of it.

Keep in mind, these circuits are only 24 volts, but carry hundreds of amps from the large 8D batteries connected in series. It's enough to melt a wrench real fast.