I'm building my first amp. Help me be safe.

Always check your filter caps before touching.
Always drain said caps before touching.
Use chopsticks to move wire if the amp is alive.
When probing while the amps is alive, keep a hand behind your back.
Respect electricity!

There's a good start.

 

I've heard this said many, many times and it almost seems enshrined in law for amp techs.
But could someone actually explain how this might save/protect you.
I assume it's some way of trying to avoid getting a big shock through the heart area (which can stop the heart), but I just can't see how it would really help. if you get a shock up your hand/arm that's inside the amp, the current would still seem to pass through your upper torso on it's way out, whatever your other arm is doing. Could someone with greater wisdom than me please explain.

 

With the other hand behind your back your not touching anything that would allow a path to ground which would go through your chest from one arm to the other. That is my understanding anyway. Might not hurt to wear shoes too that would not conduct.

 

Avoids path through your heart to ground.
Some voltages will cause your muscles to contract and if you have both hands around the amp, you might not be able to get away as you might start "grasping" the amp.

 

It's large currents through you that kill, and particularly through the chest. If you're touching the amp with both hands, especially if one is on the chassis and the other touches something live, that is exactly what will happen. Do not ever hold the chassis for any reason while working inside a live amp - the amp must be supported properly so that it can't move and doesn't need holding.

If you're only touching the amp with one hand, the current can't pass through you because it has nowhere to go out. You will still get a shock, because your body has enough capacitance that it will pull a small current into you, and it will hurt like hell, but it almost certainly won't kill you.

(This assumes that you're wearing shoes and not standing somewhere damp, too - or the current can pass out through your feet.)

It's the single biggest safety precaution you can take, because it's like a backup for all the others.

 

Ah, I understand. Then surely both insulating your feet with shoes and not sitting on a metal stool/chair would be equally important as the "hand behind the back" policy.
I just don't think I've ever heard advice such as to always wear shoes when working on amps.

 

I believe it is DSL Engineering that makes an "amp cradle" which is a nice little stand that you can put your chassis in while you work on it. The cost of the finished unit is under $100, and it's worth it if you plan on taking the less-travelled road of the tinkerer.

rooster.

 

Maybe not, but you should have. If you're working in a garage on a slightly damp concrete floor with no shoes on, you're actually at serious risk. I doubt you're very likely to, but it's worth mentioning.

Sitting on a metal chair probably wouldn't be dangerous unless your skin was actually in contact with it - your clothes are a good enough insulator (unless wet). And even then, the floor would still have to be conductive or there's still no path to ground.

A wood floor, carpet, clothes and shoes - and one-hand working - should make you safe .

I do it much more simply... put the combo cabinet or amp head box face down on the workbench, and rest the chassis, tubes-down, across it. There are very few amps which won't allow you to do this safely (sometimes it has to be at an angle, but as long as it's firmly supported that's fine). The advantage for combos is that you can then easily plug in the speakers and reverb tank as well.

 

I have always heard:

*always drain filter caps

*keep one hand in your pocket when you are working
inside of a LIVE amp

 

Have someone who knows what they are doing check it out before turning it on the first time.
Use a current limited the first time you fire it up.

 

whats the best way to drain the filter caps?? I'm considering doing some of my first work inside my champion 600.

 

The search function gave at least 3 threads on draining filter caps using just one set of search terms:
http://www.thegearpage.net/board/search.php?searchid=5494191

You might try your own search criteria if you need more information than what's contained here.

 

+1..... follow these rules EVERY TIME and just use common sense. I always stand on a rubber matt too. You're bound to be surprised and get a shock now and then, especially when you've been working awhile you may get a little sloppy. But like John Phillips said if you have one hand behind your back it won't go through your heart and probably won't kill you. Scare the **** out of you and and may have you seeing stars but probably won't kill you. So try and take breaks every once in awhile depending on your personal tolerance for concentration.

 

You need to familiarize yourself with the open AC and high voltage points, always work under good light, avoid clutter, and make sure that if you fell or jerked away in reaction to a shock, you wouldn't hit anything. Always be patient, and never use force. If you absolutely have to force something, make sure the amp is completely unplugged and drained.

 

NEVER put your lips on anything.

If you are concerned about turning the amp on then have a small child do it for you.

Never use more than 220vac.

It's ALL ball bearings these days anyway