Radio Servicing Causing Death

[dominicbeesley]

I certainly remember my grandparents not letting us touch the TV stand on their old B&W DS set!

Had had a few belts recently, a few DC ~100V barely a tickle, a badly earthed workshop and a leaky mains filter cap - quite scary when everything around you is live. I've now fixed that and permanently run all my workshop through a isolating transformer!

However, the most unpleasant and embarrassing was when showing something to a group of mates whilst fixing a lawnmower. I turned it over with the kick start.....whilst I had the spark plug out, held in my hand...DOH! Oh how they laughed at my dancing! That at least convinced them that I had fixed the ignition and the fault lay elsewhere!

Dom

[Top Cap]

I was working on a radar set in the RN and attempted to connect to a test point giving 1V video. Little did I know that a blocking capacitor had gone dead short in the unit placing -800V on the terminal. What was it like to touch that? Well give yourself a really hard and I mean, a really hard slap on the chest and at the same time place a sheet of white paper in front of your eyes. That is exactly what it is like to be on your way out of this world, I was lucky, the ship was at sea in a heavy swell. It rolled and I broke contact but had to spend the day in sick bay under observation. Thinking back, I bet it was a Hunts!

[mickash]

Shortly after starting in the TV repair trade I was present when a colleague received a very bad shock. He was pulling the chassis out of a Decca Bradford TV and managed to make contact with the aerial plug with one hand and the chassis with the other hand.
The set nearly ended up on the floor and the cry that he made while being shocked scared the wits out of me!
The poor guy was badly affected and needed to have a few days off work.
The set was on a bench that was connected to direct mains, why, I don't know but it was soon fitted with an isolating transformer.

As a kid of about 9 or 10 I remember poking a wire coathanger into an electric fire and touching the wire element. All seemed OK until the hanger also came into contact with the metal guard then FLASH BANG and the hanger was welded to the element. I didn't get a shock, not electric, that is!

I've never heard of a death in the TV/radio trade but an NHS electrician was killed at the local hospital as he repaired a tumble dryer. That kind of accident must be rare.

Stay safe,

Michael.

[Heatercathodeshort]

Its all a matter of being aware of the dangers involved when servicing electrical equipment. Forty years ago every service engineer understood the dangers of the live chassis and very few workshops used mains isolating transformers. We all received the odd 'belt' probably caused by being distracted. I once managed to change the mains on/off switch in a Thorn 1500 with the mains connected....It was only when I connected the last wire and saw a small spark and the valve heaters begin to come up that I realized what I had done! Imagine a film taken of that! The suspense!
Most cases of electric shock today are bizarre happenings such as the nail through a live cable etc. Even then that would not be such a problem if the equipment had been earthed. Its a strange combination of circumstances and I don't think any legislation would prevent these very rare cases.
When I was first in the trade, very few houses had any form of earth connection. The most common socket being a 5amp two pin type fitted with a mass of adaptors. The fuses were usually 'beefed' up to prevent random blowing. Surprisingly very few accidents occurred and this at a time when sets were often operated with the cabinet back removed by the customer to prevent frame 'creep' due to leaking capacitors when the sets became warm.
I remember reading many years ago about an engineer working for the STONES group of companies. The set in question was a Murphy V114. He was alone in the workshop during the lunchtime and the chassis toppled over resulting in the mains eht supply coming into contact with the protective metal edge of the wood workbench top. His hand was trapped and he was later discovered dead by branch staff. A good rule here may be, do not work alone when working on potentially dangerous supply voltages.
Just to prove its not all gloom and doom and we did have a bit of fun I will relate a little party trick we used to do with a pair of non insulated pliers in one hand and a fluorescent tube in the other.......No better not....
Regarding John's comment with the metal legs. I had many cases of this but fortunately no accidents due I think to the lack of any earthed objects in the average living room, this before the days of central heating and radiators. Regards, John.

[Hybrid tellies]

I can't recall anyone being killed from an electric shock, but certainly quite a few cases where people have been thrown across the room.
My worst was from a G8 power supply, I was setting it up and got distracted by someone talking to me, the next thing I new was that person and the whole workshop disappearing down a sort of tunnel. When I rocovered I found myself slumped against the bench, all rather embarrasing at the time.

[plaka78]

I had bad shock many years ago from a Ferguson 1500 that was switched off at the mains socket. The house owner had the live and neutral the wrong way round going into the main fuse box hence all the socket switches was breaking the neutral. The house in question was very run down

[XTC]

Some time back I was told about an IEEE report into electrocution which said that there was no case they'd investigated which involved less than an estimated 30mA passing through the heart.

It's the current through the heart that's the important thing.

Mostly, if you get a shock from a piece of equipment, you're wearing rubber soled shoes and on a carpet or other surface which isn't a good conductor. There's only one part of your body making a good contact and that's dry skin. There isn't a current path through the heart, arm to arm or arm to opposite foot.

If you were holding an earthed chassis with the other hand, or had it resting on a radiator, it might be a different story.

I read somewhere, the ARRL Handbook I think, that there had been fatalities with American 36V AC mains on farms. You can see it happening. Working in wet conditions with skin soaked, holding a piece of earthed metalwork for support and maybe having the tool slip and the conductor pierce the skin.

Pete.

[Bruce]

Reading this thread brings back memories. Its not just a matter of being careful what you do yourself, its often a matter of watching out for how the actions of others put one in danger.

About thirty years back when I was in the second year of my practical training with telecom Australia (the then PMG) I was in an office of a fairly large company with "my" technician (the man who was giving me the on the job part of training at this particular time) and we working on the relocation of their telephone exchange system -- which in those days were pretty complex and very weighty bits of equipment. As part of the relocation we had to move all the switching equipment and the power supply unit into another room - said unit being pretty large, from imperfect memory maybe two and a half feet long and maybe nearly a nine or ten inches high and deep, and heavy with transformers etc etc....

I'd unplugged the power supply (and the power cable went around the wall a bit to the power point), and removed it from the wall and the Reg the tech then picked it up, ready to carry it into the next room where we were going to remount it on the wall -- and as he did so the secretary who was also the telephonist came into the room, sat down at her desk and saw that something near her desk was unplugged. She automatically grabbed the lead and plugged it in - lighting up the power supply and, inadvertently, also lighting up poor old Reg the tech who had just picked it up.

He just flew up in the air yelling and was just jumping up and down trying to throw the PSU down - and heavy as it was he couldn't throw it down -- I guess he wasn't plugged in too long as I grabbed the lead and pulled it out of the socket and he just crumpled to the ground. He lived, but he shook for a long time afterwards, and had deep burns on both hands, and after medical treatment had some weeks off work. I don't remember much more about it than this but it was a bit of a wake up call at an early age regarding what the hot stuff can do if you grab it too tightly...... I suspect that over the years when I'm working I'm always been more concerned about what others are doing around me than I have been about my own prodding the hot stuff.....

bruce

[Skywave]

Reviewing these Posts has reminded me of what was - probably - the closest call I've ever had with radio servicing, many years ago.

Radio was a communications-type receiver. A previous owner had replaced the 6X5 FW rect. valve with a solid-state rect. assy. This consisted of a pair of BY100 diodes with a current-limiting resistor in series with each. These components were mounted in the base of an old Octal valve - thus enabling this modification to be easily 'undone'. So far then, so good.
What was not good was the fact that at the junction of each diode and resistor, there was no insulation whatsoever: these junctions sat well-proud of the periphery of the valve base.

So - when following the completion of a servicing session - with the receiver upside-down - I then attempted to rotate the set the correct way up, having unplugged it from the mains socket first. The set - being of the traditional all-metal construction - was heavy: therefore, right-hand on the metal cabinet on the front right, left-hand on chassis at its left rear.

Wallop! Finger of left-hand came into contact with aforesaid exposed joint - which, or course, with the set in the upside-down position, I couldn't see. Full whack from the PSU reservoir capacitor from left-hand across chest to right-hand, whilst firmly grasping the metal chassis / cabinet with right-hand.

Next thing I remember was 'coming to' in a crumpled heap in the corner of the room. Fortunately, I - and the radio - survived - although I still have the scar on the finger where the wire of the junction cauterised & burnt into the skin.

Oh, yes - I still own the radio - but it now has a substantial paxolin tube fitted around the said valve base - which I inspect thouroughly prior to any service session. I do NOT want a repeat of that experience: I might not be so lucky next time!

Al / Skywave

[The General]

In the mid-eighties, in a previous job, one of the other engineers there showed me his party trick. He plugged in a 6A IEC 'kettle' cord, switched it on at the socket, then quick as a flash before I could stop him, popped the other end into his mouth & held his hands up in a 'look ma, no hands' pose. Of course, he was holding the body of the connector between his teeth. I winced & called him a stupid but all he did was pull out the connector, grin & say '& people say mains is dangerous'!
What a berk.....

[michamoo]

That is just madness!

[stevekendal]

Not radio servicing, but safety-relavent I think. Many years ago, when I was just a teenager and we had holiday flats in Morecambe, My mum and gran were getting the first floor flat ready for the incoming tenants, when mother decided to clean the heat reflector on the 2-bar electic fire. This had one bar permanently on and one switchable, so seeing as the fire was cold, she removed the wire guard and thrust her hand behind the bars to remove the dust. I have always been glad that I wasnt there to witness the scene, because yes, you've probably already guessed, the permanently-on bar was o/c the fire plugged in and mum's hand was stuck to the bar. Luckily, gran was cool-headed enought to suss what was happening and pulled the plug (a wylex). They were both very shaken by the experience and mum's hand was burned down to the bone and took weeks to recover. Never take anything for granted with electricity. Mains supplies too can be a hazard if botched. A friend complained that whenever he conected his Bush SRP31 record player to the optional stereo adapter, there was a bang and the fuses would pop. When I went to have a look. he was using two different power points. One had live and neutral reversed and one of his mains plugs had neutral and earth wrong. Kaboom when you connect the signal lead. Steve.

[ianj]

I got a belt once at work, from broken down insulation in a damp underground room. The room felt"charged", odd...............we disconnected and completely rewired everything. This was just as the 15th edition of the IEE regulations had come out (1983??) and lots of thingds on London Underground were iffey(probably still are) ianj

[GLENZ32]

Hi all, newbie here to the forum, I've never heard of anyone myself being killed as a result of working on a domestic radio or tv, but there sure is a lethal potential there in any case and it does pay to be careful and cautious when working with any electronic device that is mains derived, all it took was one decent belt accidentally from 240V several years ago to wisen me up in that respect. I guess us tech's have all had our fair share of shocks from appliances in the past....Usually followed by various swear words of all types.....8-

I learnt at a very young age about HT after retrieving a Philips F2ZN b/w Tv from the tip and of course the first thing you do is take the back off and 'plug it in' to see if your rescued treasure will work..... the valves light up, theres a small waiting period, there seems to be sound but no picture, one starts poking around in the EHT section totally unaware of anything dangerous in this area, thinking theres a loose valve then the line oscillator kicks in along with the line output stage and while this is taking place some small fingers are in between the PL504 and PY88 top caps, well you all know the rest.........small kid turns the TV off and runs away from it screaming! HAHAHA....

All jokes aside, I treat any high voltage/HT supplies with the utmost respect, it doesn't pay to be foolish...Theres my two cents worth...

Cheers! great site by the way.
Glen