Belter from HT

[G6Tanuki]

A while back, I leakage-tested a bunch of big 100uF 450V-working electrolytics - a day later when I came to fit one, it bit me.

Also, in the past I worked on a commercial/military HF transmitter where to change frequency involved rotating a coil-turret in the driver stage. Officially you did this by powering-down the transmitter, unscrewing a cover-plate [whose removal tripped an interlock that shorted the +1250V HT-line of the driver to earth] and then used a supplied tool to crank the turret round, before reassembling.

In service, *every* one of these transmitters had the interlock bridged, and the cover-plate resting in position. Old-hands had realised that the majority of the metalwork under the cover was not at +1250V and would change frequency 'on-the-fly' by reaching in to flick the turret-block round the necessary number of notches.

Get it wrong, though, and you got a hell of a belt. Of course, the edges of the hole you reached-in-through were sharp and it was not unusual to see someone with the skin on their knuckles missing . . .

[terrybull]

I recall when I was about 15 so a fair time ago we had a bush record player and I leaned down to pull fluff off the stylus and the spindle you place the records caught up the inside of my nose as I tried to visually check the stylus. Not sure why but it was a very nasty belt. Made my head buzz for sure and probably explains a few things🤕. I have been very very careful indeed since then.

[hannahs radios]

My worst belt was from a 3.5 Kv pulsed powersupply we used for insulation tests on transformers the second worse was from the HT s7pply to the tube base on an instant picture telly I was given to play with I had no isolation tranny or even an RCD so I think I was lucky ish

[Lloyd 1985]

Oh yes... getting a belt off things used to be one of my past times!! The one I remember well, because it was off something daft, was my Sega Game Gear, This little innocent looking device, powered by 9V, hides a nasty nip inside! The colour LCD display was backlit by a small fluorescent tube, and there was me not knowing that it required a few hundred volts to light it! So I touched both ends of the tube whilst it was on... I was only young! I couldn't understand it, it only runs off 9 volts, and I've never had a shock off a 9 volt battery before!! it was only later in life I discovered inverters, 9V in, a lot more than 9V out.

The next most ridiculous one was from a Bush 14" colour portable telly with a dodgy LOPT, it used to arc out of the LOPT casing, and I got too close, it bit me, then I picked up a screwdriver and it arced to that too, causing me to chuck the screwdriver away, then whilst retrieving said screwdriver it bit me again! I turned it off after that...

When doing any electrical work I always stick a meter across whatever I'm about to work on before touching it, even if I've just been and turned off the breaker. I just like to make sure it's dead before I touch it! I did encounter one crazy 'qualified' electrician who decided it was a good idea to cut through live cables, his excuse was he didn't know which breaker was for which circuit on our breaker box... If he'd bothered to ask, or look around there was a chart detailing what was what! It made quite a bang when he did it.. Twice as well!

Regards,
Lloyd.

[Zelandeth]

Have had a few. Notable ones being:

[] Philips 22" CRT computer monitor EHT. I shot backwards across the room, backflipped over the bed and into the bookcase which took exception to this and then collapsed on me. After about ten minutes I managed to unearth myself, and a couple of hours later got the feeling in my right arm back.

[] Kolster Brandes KV024 HT rail I think. Was hunting a dodgy contact with what was meant to be my "prodding live things stick" (BIC biro with the pen bit removed), unfortunately for me I'd reached behind me and picked up a pencil instead. That hurt like blazes and I had a perfect circular burn mark on my hand that took months to fade.

[] 3 phase 415V. My own stupidity combined with an idiot engineer leaving the cover off a junction box. I would have been more careful of the connection in question had I known at the time that the black wire was now a phase rather than the neutral due to the new colours! Landed on my head in a box of potatoes. Rcd tripped, but I'm not 100% sold on its response time. I wasn't even working on anything there, just trying to get stuff out of an overcrowded store room where you had to squeeze past a refrigeration compressor and I lost my balance and brushed against the aforementioned terminal.

...then had to spent the next couple of hours reprogramming stuff that got tripped out by the RCD - with a raging headache.

Think the only other ones I've had have been getting nipped by smoothing caps which held charge longer than I expected.

Oh...actually just remembered another one which was up there in the pain category. Picture this. You're working on a bus (Bedford YNT) investigating an intermittant starter switch. It's only a 24V electrical system and being a diesel there's not even an ignition system to worry about, so you consider it "safe." You can imagine my surprise then when releasing the key from the start position holding the meter probe in place with my finger when I got a really beefy belt that sent the meter half way up the coach. I lept out the door and immediately started hurling insults at the coach, while my mate was literally rolling around on the floor laughing. Took me a few minutes (once my eyes had stopped spinning) to work out what had happened. When I disconnected the supply to the (large, this is a bus mind) starter solenoid, it does that thing inductive loads do when you disconnect them...and generates a whacking great voltage spike as the magnetic field collapses. Normally this would have nowhere to go, but on this occasion it had a nice bleeder resistor via my right index finger and out through my backside where I was sitting on the metal plate containing the windscreen heater controls. That one got major points just for sheer surprise and it was a really meaty belt. Won't make that mistake again though!

[Andrew B]

I was casualy neutralizing a pair of 813's set up in AB2 and the probe slipped with my other hand on the case.

I left the skin of my right palm and fingers on the chassis and to this day I don't know how the hell I got away with it. 2200v and 32mF. (modified microwave transformer)

Since then i have never run anything that required proper "high voltage" live working"

My first tickle was re-inverting 12 volts into the secondary of a speaker transformer and grabbing the primary leads.

Could we have this as the "sticky" of those who "do not read warnings/choose to ignore warnings/I am not complacent/Darwin bait" please?

[Peter.N.]

After 50 years of servicing TVs shocks became a way of life but the worst one I ever had was from my FT 101 ham radio, I grabbed the anode cap of one of the PA valves after the set was turned off and got 900 volts across my fingers from the smoothers, burnt two holes in the ends of my fingers which took weeks to heal.

With all my previous shocks I have just carried on working but this one knocked the stuffing out of me.

It was my lack of knowledge that caused this, the only transmitters I had previous experience with were PMRs and on those there was only HT on the PAs when they were keyed up, I assumed the Yaesu was the same - much to my injury.

Peter

[Andrew B]

Originally Posted by Peter.N.

I assumed the Yaesu was the same - much to my injury.

That Class A or B always gets you

[Lucien Nunes]

the black wire was now a phase rather than the neutral due to the new colours

But the neutral should always be treated as potentially live wrt. earth. Hence the new terminology: Neutral (blue) and Line (brown/black/grey) are all Live Conductors.

When doing any electrical work I always stick a meter across whatever I'm about to work on before touching it, even if I've just been and turned off the breaker.

A multimeter is not a good substitute for a GS38 approved voltage indicator. There are too many opportunities for misreading or error, it is not reliable enough in practice to indicate safe disconnection.

being a good sparky my mate put a screwdriver across them

A screwdriver is an especially bad substitute for a GS38 approved voltage indicator!

The safe isolation and lockout procedures used and mandatory in electrical inductries seem to have evolved for a reason. QED.

[paulsherwin]

Some sparkies are amazingly cavalier about safety. I was once working in a large office sorting out some network cabling. There was nobody there but me and a sparky doing something to the 3 phase distribution panel in a boxroom by the doors. There was suddenly a very big bang, a very white flash and all the power went off. I found the sparky off his stepladder at least 8 feet away, covered with soot and very dazed. Fortunately there was no serious harm done but that was just a matter of luck.

[Techman]

The worst belt I ever got was when I was a youngster, from an old Murphy radio that had been in the family since new. I was messing about with it in our garage with the back off and I was standing on a concrete floor. Everything was going fine until I decided to make some internal adjustment, but just to be safe, I switched the set off at the on/off switch on the front of the set, still leaving it plugged into the wall socket. This was a ‘live chassis’ type set and although connected correctly with neutral going to the chassis, I hadn’t realised that only one of the poles of the on/off switch was ‘breaking’. Only the neutral connection was being switched so that when the set was switched off, the chassis instantly became live to mains. I was touching the metal chassis without problem while the set was switched on, but received one of the worst shocks I’ve ever had in my life from the chassis metal work as soon as I’d switched the set off.

This is why double pole switches can be so dangerous on live chassis sets if either one pole fails shut, or both poles don’t break at exactly the same time. I remember my mother used to complain that she sometimes got little shocks from the end of the aerial wire that was strung round the window frame in our old kitchen where the set spent its previous life – set now long gone, shame!

[Tractorfan]

Hi,
I've had belts from many sources during my misspent youth, and beyond. Mains, HT, EHT, car ignition, charged caps, et al.
I was reaching carefully inside a steel cased Pamphonic PA amp back in the eighties and my palm caught a tag strip carrying HT. Of course, I jerked my hand away and smacked my knuckles against the case. My reaction was to pull my hand away from the case and ... you guessed it ... back on to the HT again. The cycle repeated a couple of times before I got my hand out!
Cheers, Pete.

[mole42uk]

Originally Posted by paulsherwin

a sparky doing something to the 3 phase distribution panel in a boxroom by the doors

It sounds like he was applying for a Darwin award.

I wonder what his Risk Assessment for that job looked like, and why he thought working on live equipment on his own was a good idea?

[Herald1360]

Also sounds like no risk assessment and no thought either!

[AC/HL]

Originally Posted by Tractorfan

The cycle repeated a couple of times before I got my hand out!

Sounds like something by Hoffnung!

[Hybrid tellies]

Like a lot of people I have had a few belts in my time and thankfully learned from my mistakes. The worst I ever had was from a Philips G8 stabilised DC power supply. Whilst I was setting up the HT I was also talking to another workshop engineer. All I can remember is his face disappearing down a tunnel, then seeing the rest of the workshop re appear back through the tunnel. Bit shaken but was ok.

[stevehertz]

Having worked in an electronics production test department for 12 years, I have had my fair share of shocks - HV AC and DC - hundreds I'd say. I can't help but think though - and not wanting to be a spoilsport - aren't we just glorifying and dumbing down what can be a fatal incident? Any newbie reading this is going to walk away with the impression that a shock is something that you just shrug off and laugh about later. Well, mostly yeah, but.. A close friend of mine who still works in electronics works with guy who lost an arm to a powerful shock. Ok, he didn't get it from working on a DAC90, but surely we have to be clear about electricity and its dangers?

[Sideband]

Some months ago I was using the differential probes with the scope at work. I was getting some odd readings and then noticed that the battery indicator light on the probe was flashing (flat batteries). I went to the store room to get 4 AA batteries and then proceeded to change said batteries......

The probe was still connected to the power supply...across the primary of the switching transformer....about 360V.....!

Can anyone say they have had one hell of a belt from a set of AA batteries?

There is a warning flash on the back that says, 'isolate before changing batteries'.....now I know why!

Better never to get a shock and look a bit 'cissy' than to get that fatal one. There is "relief laughter" afterwards, but no joke. I have had a few tickles from valve kit (more from battery stuff, you think it's safe, wrong) but never a real belter of a shock, nor do I want one.

Three (at least) things I do...
Left hand IN POCKET when accessing (measuring) known live equipment (yes, I know I said this earlier, worth repeating)
Short out anything you are going to work on.
Put the plug of a pluggable device in the other pocket.

[paulsherwin]

Originally Posted by stevehertz

Having worked in an electronics production test department for 12 years, I have had my fair share of shocks - HV AC and DC - hundreds I'd say. I can't help but think though - and not wanting to be a spoilsport - aren't we just glorifying and dumbing down what can be a fatal incident? Any newbie reading this is going to walk away with the impression that a shock is something that you just shrug off and laugh about later. Well, mostly yeah, but.. A close friend of mine who still works in electronics works with guy who lost an arm to a powerful shock. Ok, he didn't get it from working on a DAC90, but surely we have to be clear about electricity and its dangers?

I agree that it would be wrong to give the impression that HV shocks are trivial things to be laughed off. While they are rarely fatal from consumer electronics, they are usually extremely unpleasant and to be avoided for that reason alone.

I'm sure that all of us who have received a significant belt have no wish to repeat the experience.