I'd have to say that the worst tool for an electronics job is probably my index finger.

When I was younger, just starting out in electronics, I had a passion for building kits. It was supposed to be a gentle way to get yourself acquainted with the art of reading component values, populating boards, soldering, clipping leads, testing, troubleshooting and providing the finishing touches with as little risk and as much convenience as possible.

The first mistake is a very common one - I was soldering a PCB pin to a board as an attachment point for a wire, as I was instructed to do. Not having a set of helping hands or anything, I shoved the pin into the board, held the pin down with my index finger firmly while gripping the sides of the board with the same hand, and using the other hand grabbed the iron and the solder and began to solder the pin. Needless to say, I immediately grasped the concept of thermal conductivity when I grew a blister right in the middle of my index finger ... making work more painful for about a week.

I thought I'd learned the lesson, but then, I got caught again when it came to tinning a short piece of wire. As I had a crummy thermally-balanced iron, heating times were a little inconsistent, so I was holding the wire at the insulated end and tinning the stripped end. Needless to say, the insulation eventually gets hot and melts as well ... giving me another burn. Add that to inadvertent soldering-iron contact when I used one without a stand ...

Many years passed and I became more experienced at soldering. Being burned by the iron became a thing of the past. But just last year, I burned my index finger again. This time, it was a bit of a funny story - I usually hold solder with the left hand, feeding it into the iron on the right. Well, on my bench, I had a scrap of 0.8mm 60/40 solder, and a scrap of 1mm tinned copper wire. Guess which one I grabbed and tried to feed into the iron? I was a bit frustrated as it seemed to be taking forever to melt ... and then the heat got to me! D'oh!

Sometimes, it's not the iron's fault. I have another habit - namely of testing the temperature of something with my finger. Having built a kit, I got a diode in the wrong direction and it shorted out the supply voltage, crowbaring it down to zero. I was wondering what was taking all that current, so I started touching components to see which ones were hot. Needless to say, I burnt my finger on an 1N4004, which taught me a lesson - perhaps use a less important finger instead ... or get a thermal camera.

But the finger also has a number of remarkable properties - being conductive and attached to the body, I've gotten zapped by touching things and I've also zapped things (e.g. MOSFET gates) by touching them through ESD. My fingers are dangerous.

- Gough

Those are great and funny stories, thank you for sharing them.

I'm sure by now you've perfected the "finger test of hot items" as, the brain telling finger to touch surface, brain says to move finger off surface and brain then thinks about if it was hot: for reasonable hot temperatures this does indeed work. What doesn't work is brain tells finger to touch surface, brain thinks about how hot that is and then brain tells finger to move off. And if using the first method nothing registers then a succession of quicker taps ensues to gauge the actual temperature.

14rhb - I find it best when you outsource the finger jobs to someone else . Hey, umm ... does this feel hot to you?

- Gough

I've certainly tested something for heat in the past - wet my finger too to get the 'sizzle' before it really burned . . . . . . unfortunately it was the case of a TO3 transistor (the carbon resistor downstream was doing a passable impression of an arc lamp).

I didn't notice the label on the TV chassis  "Warning, Chassis Live Regardless Of Mains Polarity"    -    it was hot alright, hot to the tune of 240V ac mains!

Maybe I should steer clear of electrics/electronics . . . . 

Wow, that's brave. I think our first TV always gave a mild tingle when changing channels on it, so I tried to stay clear of the insides of those : )

But on home-made circuits I sometimes used to use a lip test on TO-18 cans to see if they were gently warming up : ) But sometimes the heat rise was quite rapid with those : )

Wow, that's brave. I think our first TV always gave a mild tingle when changing channels on it, so I tried to stay clear of the insides of those : )

But on home-made circuits I sometimes used to use a lip test on TO-18 cans to see if they were gently warming up : ) But sometimes the heat rise was quite rapid with those : )

Brave Shabaz? or stupid . . . . . .