Some electrical safety for our newcomers

I know that there are often questions from new hobbyists regarding safety, so I thought I put up a post with a couple of the basics. Also I know this post is a bit lengthy, but if you are new to this, please take a moment to review what I have posted. You might be quite glad you did later.

The first basic rule is to simply pay attention and know what you are dealing with. Always pay attention. Seems basic enough, but even I didn't follow that rule a couple months back. I had went to unsolder a part connected directly to the power cord of a piece of test equipment. I had just plugged it in to check it out, knew I needed to change this part, but I got distracted for a moment and had to step away from the bench. I came back and proceeded to put the soldering iron on the connection, and got a big bang and sparks. I had forgot to unplug it first.

When I say keep in mind what you are dealing with, that is it is very common for these old sets to have well over the 120 volts from the line running through them. You can expect to have over 300.

Pay attention to electrolytic capacitors. Any capacitor can be dangerous when charged. They can shock you. But the other part with electrolytic is they are polarized, that means that positive MUST go to positive, and negative to negative. If you reverse it, refer back to the big bang. (But no sparks)

The last thing I will point out (for now) is Variacs and isolation transformers. A Variac is simply an adjustable transformer that changes the voltage coming out. You can start on 0 volts and adjust up to line voltage (or more on some models). You plug it in the wall, and plug the radio into the the outlet on the side of the Variac. Whenever you have a radio that you have never run before, ALWAYS inspect if first for any broken wires or insulation, then if that all looks OK, plug it into the Variac, set it on zero volts, turn it on, and slowly bring up the voltage. If your set starts to show signs of smoke, or loud improper noises, cut of the voltage and proceed to repairs.

That leads us to the isolation transformer. A transformer is simply two wire coils back to back. Two electromagnets. Normally they increase or reduce the voltage, but in this case the voltage coming out is the same as what goes in. However because they are two separate coils, there is no physical electrical connection between the line outlet and what goes into the set. So how is this a safety item? Well, think of this. Let's say you plug the set straight into the wall outlet. As you are making adjustments to the set, you accidentally touch a hot wire inside. If your other hand happens to be touching a ground, you will now have a complete circuit across your heart. This includes if you are touching a piece of test equipment of the like. It's a lot easier to do than you might think. With an isolation transformer, wall ground to radio guts are not a complete circuit.

If anyone else wants to add some safety notes, this might be a great place.