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This is one I feel should be covered, especially for the young blood in the community.
Lets be honest we have all been at the point where we do not have a clue of the dangers and there are a lot of people out there attempting to work on hazardous projects or repairs not fully aware of the risks.
General risks should be covered, but also more importantly the more obscure risks ranging from electrocution hazards to dangerous materials used in electronics manufacturing.
Tell me what you think on this subject.
Have a happy and safe time engineering guys and gals
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With most low voltage electronics there is not much of a safety risk with the possible exception of large capacitors.
A soldering iron can burn you if you are not careful.
Watch out for moving parts (say from a motor). You do not want to get hit by something.
If you smell or hear anything out of the ordinary stop what you are doing and reassess.
Working with higher voltages (both DC and AC) is where you get hurt. If the item is AC mains powered then make sure it is disconnected first. It is a good idea to always double check things and use a meter to verify that there is to voltage present in your system.
Having a first aid kit, a fire extinguisher, using eye protection, and washing hands after working is some general good advice.
Any time you work with a chemical you need to watch out (cleaners, flux, PCB-from-scratch-chemicals, etc...)
This list is just off the cuff... -
One of the potential safety issues new (and old) people face is cutting component legs with side cutters and getting hit in the eye/face.
Because the width is quite small, the speed quite fast and ends quite sharp they can easily embed themselves in soft things.
Blunt cutters don't really have this problem. They can't cut through the entire component width at the same instant, meaning they can't transfer your cutting grip force into velocity.
However get some nice Lindstrom cutters (or other good brand) and you get a satisfying click as the wire cuts followed by pings from the other side of the room as the bit of metal bounces off the walls. -
i strongly agree, smell and sound are the best possible things to keep track of if i circuit is being tested,
The one hand rule is also a good one as long as your seat and desk have rubber feet, you can be charged up to 10Kv above ground and will be happy as larry until you touch something more than 50V below or above that potential, with your other hand,
use tweezers / pliers when soldering large or thermal padded packages as they not only take a while to loosen but can burn you a good 10 minutes after removal / fitting,
point a fan across your desk if you cant afford a fume extractor, so that most of the flux fumes dont end up in your eyes and on your face,
isopropyl is a golden fluid for pcb and enclosure cleaning, it does dry out your skin but its not harmful, short of you drinking a significant quantity of it,
set up your equipment and then apply power, this doesn't necessarily mean completly turning on and off your supply, but if your load has any kind of input capacitance it can spark, and if the current is high enough, burn you,
do not get into the habit of flicking the iron tip when you start off, get a sponge, lightly moisten it and wipe on that instead, remebering leaving some solder on the tip before you switch it off extends its life, equally dont let too much build up on the tip, depending on the blend when it drips it can splatter quite wide.
when cutting leads, place your finger against the edge of the piece being cut off, this absorbs most of the energy of the cut and stops it shooting off (i have seen very bad things happen due to this)
if you can, get a helping hands, they allow you to work on the pcb at more convenient angles which means your less likely to grab something that is hot,
when designing as a hobbyist, if you can try and aim to keep everything under 50 degrees C, such as doubling resistor wattage values and such, it keeps it safer for you, and will make the device last longer in general,
wipe your boards with a cleaning alcohol if they have been allowed to oxidize, this will help prevent the solder from forming big blobs without actually tinning,
there are others i can list, but i feel this is getting a bit too long :/ -
How about "young players" wanting to design a transformerless mains power supply (because those are bulky and expensive), for their project? The type with only a capacitor, resistor and a diode?
And however tempting it is to loosen those screws in them, do never open RF attenuators because of Beryllium oxide use. When these devices malfunction, it is probably because of internal physical damage and you don't want to inhale the dust from that.
Safety Hazards in Radio and TV Repair
Having mentioned all that, many people new in the field of electronics don't want to hear the constant warnings for danger from the more experienced. I think the most dangerous aspect of electronics is that you can't see electricity, no matter how hard you look. -
Having mentioned all that, many people new in the field of electronics don't want to hear the constant warnings for danger from the more experienced.
I think that's just the attitude of the world today, 'you can't tell us what to do, we have rights' and all that. Some people take it a bit too far/out of context. -
I will add that batteries can be very dangerous. Lithium cells are potentially explosive if misused or cut open, or used without a protection circuit. Most rechargeable cells can deliver enough current to heat things to red heat, even when close to discharged. Alkaline cells the same, they also can leak out corrosive material that will destroy most metals and discolour a lot of plastics if left in contact with them for any length of time.
Lead acid cells are not sealed, they vent hydrogen gas and if misused they vent acid vapours as well. they also can deliver very high current into a short circuit, and this can cause the cell to explode from gas build up. -
Having mentioned all that, many people new in the field of electronics don't want to hear the constant warnings for danger from the more experienced.
I think that's just the attitude of the world today, 'you can't tell us what to do, we have rights' and all that. Some people take it a bit too far/out of context.
On the other hand, I think the majority of the visitors here have zapped themselves (and burned a finger on a hot semiconductor) at least once in their lives and apart from a loud "OUCH!" and optional shaky knees have no permanent injury. Or is that due to a Darwin selection thing? -
well your hardly going to die from burning your finger, now dont take this the wrong way, but on dry days mains can hold such little influence that it just feels like a tingle, and you can walk away smiling, its the other cases where they get a very bad jolt that ends up frying them or hurts their pride enough that they avoid it from that point on,
You should not fear mains, but treat it with respect, you have a high voltage and very low impedance supply capable of supplying surges of 1000's of amps, and i would strongly say a transformer with a soldered and heat-shrinked IEC socket is the closest a beginner should get to it while he is learning, as even if its a 1:1 its a current limited on the output,
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Always discharge capacitors that operate at high voltages with an appropriate resistor before working on the circuit.
Use a 5W wire wound type resistor or similar 1 K ohm or higher. -
One thing that needs to be covered is what I call "electrophobia" which is thinking everything to so which electronics is dangerous. One of the biggest dangers is although something is disconnected from the mains capacitors may still be charged up.
When running low voltage old gear which lcds (say pre 2007) the backlight inverter can hurt you I learnt this when running a portable DVD play while it was open I felt a large pinch ok it won't harm you much but it is something to be swear off.
I have been doing electronics for about 8 or 9 years now and never had to use anything about 12v so u don't need to use dangerous voltage. The only thing that you need to be careful with is exploding batteries and caps so alwase chose caps which are rated for atleest double your voltage and handle your batteries with respect. And also soldering irons can be dangerous just treat them with respect -
The list is end less.
There are lot of heavy metals in electronics from lead to mercury and a few obscure materials only chemists then to know what they are.
Always wash your hands after an electronics session just to remove any potential remains of these substances. Most are contained in the components, but there are times when we get curious or a miscalculation occurred and something goes bang exposing these hazards.
To know the hazards means one can take precautions to protect themselves and others involved in the lab. -
No project is worthwhile unless you've shed a little blood over it. Keep Band-Aidstm (plasters?) handy. Unused toilet paper and electrical tape are a usable substitute in a pinch... Superglue can seal a small cut but it stings a lot. Disinfect the cut before you seal it shut.
Solvents in open cuts do not feel good. Keep your fingers out of the way of sharp edges. Be especially careful with Exacto knives, they can cut DEEP.
Don't strip wires with your teeth. On the same note, it's generally not a good idea to use your teeth as a third hand holding the solder. You can burn your lips.
Screwdrivers are designed to tighten and loosen screws. Prybars are not screwdrivers, and vice versa. Nor are they chisels or punches.
Rings and wristwatches off when working with live equipment, and they can snag on things when you need to move quickly. I cringe when I see Dave working on gear while wearing his watch. It's a good habit to get into to slip your ring and your watch in your pocket when you first sit down at your bench. Yes, most watches are now plastic cased so the shock hazard isn't there anymore but - there are still dress watches with metal bands and cases and if you aren't in the habit, one day it may come back to bite you. Get a ring caught between poles of a battery or power supply without current limiting and you can guess the effect of Ohm's law.
CRTs are extremely dangerous. Besides the high voltage hazard, they contain very high vacuum, and have the bad habit of imploding if handled roughly. You don't want to be around a CRT when it implodes. Same, to a lesser extent, are vacuum tubes/valves. Most convert into very thin glass shards which are somewhat difficult to pick out of your palm and fingertips when you sweep it up with your hands after you drop one. -
The biggest risk in electronics is driving to the store to buy parts
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CRTs are extremely dangerous. Besides the high voltage hazard, they contain very high vacuum, and have the bad habit of imploding if handled roughly. You don't want to be around a CRT when it implodes. Same, to a lesser extent, are vacuum tubes/valves. Most convert into very thin glass shards which are somewhat difficult to pick out of your palm and fingertips when you sweep it up with your hands after you drop one.
Re CRT implosions---if you were writing this in the mid 1950s,there might be something in it,but TV type CRTs from the very early 1960s on are designed to minimise the chance of this occurring.
In over 40 years of Electronics work,I have never seen any type of CRT implode.
Oscilloscope CRTs,aren't as well protected,but they are smaller,with proportionally less stress on the tube.
Vacuum tubes are no more dangerous than ordinary light bulbs.The glass thickness is greater than a light bulb,& implosion is not a problem with normal receiving type & small transmitting tubes.
There may be a few very rare ones with extremely large envelopes which could implode,but that would be unusual in the extreme.
I have seen many vacuum tubes dropped over the years--old style octals & 6 pins will indeed shatter,but miniature 7 & 9 pin very rarely do.
I have dropped such tubes on concrete,& although the envelopes crack,the thing is more likely to roll across the room!
It would be extremely silly to try to sweep up any broken glass with your hands.
I've already addressed the question of TV CRT EHT a number of times on this forum.
Painful?,Extremely unpleasant to experience?---Yes!
Likely to be fatal?--No! -
Congratulations on making it 40 years + without ever working with idiots.
Re CRT implosions---if you were writing this in the mid 1950s,there might be something in it,but TV type CRTs from the very early 1960s on are designed to minimise the chance of this occurring.
In over 40 years of Electronics work,I have never seen any type of CRT implode.
Oscilloscope CRTs,aren't as well protected,but they are smaller,with proportionally less stress on the tube.
If you're saying modern CRTs don't implode, there are about a dozen Youtube videos that would prove you wrong.
I've been in the business over 35 years and I've seen a few things myself, so don't be so quick to judge. I have personally been around a CRT implosion due to mishandling. Didn't cause it but had to help clean up the mess afterward. In my experience, the most hazardous time in a CRT replacement is just after it is removed from the enclosure - people sometimes forget that a CRT can hold a charge with the power off. A naked charged CRT on a steel deck is a recipe for disaster. Or at least quite a few crunchy bits underfoot.
TV type CRTs have an implosion band/strap to help prevent it from happening. However, if you've ever worked on a maritime RADAR PPI display from before the raster scan era, you would know that the old round P7 phosphor tubes were very fragile. Same with certain high resolution P5 phosphor CRTs used in film recorders prior to the advent of Powerpoint and LCD projectors. Oscilloscope CRTs vary. It always seemed the more expensive the tube, the more fragile it is.
In one of the first shops I worked in out of tech school, we had a specially constructed plywood safety enclosure in which to place phosphor burned CRTs when venting them prior to disposal. We even had written procedures on how to place the CRT in the box face down, put the cover on with just the end of the neck protruding through a hole in the lid, then snap the vent tube (on the earlier ones break the Octal center pin to get at it) to let the air in. Do it wrong: POP, and the box is immediately filled with shards covered with phosphor and aquadag. Do it right and listen to it whistle and hiss for 20 minutes before packing it in the box its replacement came in, then pitch it in the dumpster. I don't think anybody does this anymore.
Now when it comes to safety, this attitude of "it can't happen" is exactly what gets people injured or killed. The chance of someone reading this and then working on an old scope or antique TV are quite high, so you are doing them a disservice by saying there is no hazard. I will agree that the odds are pretty slim; but they multiply rapidly in the presence of idiots and untrained personnel.
The point is, when you're working with this stuff, think ahead, be extra mindful of yourself and your surroundings, and don't take anything for granted. Think about the process before you loosen the first screw, for example, where are you going to set this thing down once you get it out of the case, so it doesn't slide off the table and hit the floor? You don't have to be frightened of a CRT, but it is best to have a healthy respect for them and treat them with extreme care.
In my experience there are only maybe two things more hazardous in the electronics field than a CRT: one is transmitter high voltage - particularly multi-kilowatt power amp B+ where if you're working with the interlocks disabled you need to keep one hand in your pocket, and the other is tower climbing. I have lost two friends from collapse due to structural failures on small towers on two separate occasions. Neither were professional climbers and in both cases it was not their own but a friend's tower that killed them.
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I always pop the pip off the tube as well, generally inside a wheely bin, so as to contain the glass in case of an oops. then when it finishes venting I break the tube neck off and flatten it down with a large hammer so as to reduce the glass to a thinner pile. Fun on the bigger monitors like a 19 inch or bigger or on a TV CRT. Those CRT's are very heavy, and are very awkward to handle without having a tube lifter ( a heavy steel wire with a handle that you put in the lifting lugs so that you have a firm place to lift it out of the chassis) as then you cannot grip any safe place. Always lift a large CRT and handle it face down.
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The list is end less.
There are lot of heavy metals in electronics from lead to mercury and a few obscure materials only chemists then to know what they are.
Always wash your hands after an electronics session just to remove any potential remains of these substances. Most are contained in the components, but there are times when we get curious or a miscalculation occurred and something goes bang exposing these hazards.
To know the hazards means one can take precautions to protect themselves and others involved in the lab.
Thank god my other great interest is chemistry and I love it when chemistry and electronics overlap -
Electronics, where you get all the fun of organic chemistry and inorganic chemistry in the same package, and have to deal with both, along with metallurgy.
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One thing that needs to be covered is what I call "electrophobia" which is thinking everything to so which electronics is dangerous.
I used to be really frightened by mains.
This is why:
When I got my first multimeter, must have been 14 or something (got scammed by a local hardware store and paid 30€ for a shitty DT-830), I wanted to measure everything. I started with battery voltages and all that jazz, then I measured current through some LEDs and then I got curious what is the exact voltage in our outlets was. I put the meter on the floor in front of the outlet, crouched, grabbed one probe with each hand and slowly poked into the outlet. There was a glorious explosion inside the meter, a bright flash, a loud bang and a thud of my butt hitting the floor, when I jumped backwards. You probably guessed it, I forgot to plug the probe back into the voltage socket.
The meter was FUBAR, the one of the probes' cables literally got blown off and there was a small chunk missing on one probe tip. The circuit breaker was obviously triggered.
I overcame the fear after I designed my first circuit that used mains, I think I was 16 or so.
The moral of the story is: Most meters don't beep at you, if your probes are in the amp jack when you want to measure voltage. Check before you measure.
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The moral of the story is: Most meters don't beep at you, if your probes are in the amp jack when you want to measure voltage. Check before you measure.
Check twice measure thrice -
RE: glass exploding..
There's a cool video around somewhere where someone drops blobs of molten glass into water and it solidifies in long tear drop shapes.
Because it's cold the surface glass sets first and the glass in the center solidifies later under extreme stress.
The shape is quite strong on the large end, you can hit it against things, but if you snip off even the tinniest bit of the tail the whole thing instantly explodes everywhere in many pieces. -
Re CRT implosions---if you were writing this in the mid 1950s,there might be something in it,but TV type CRTs from the very early 1960s on are designed to minimise the chance of this occurring.
In over 40 years of Electronics work,I have never seen any type of CRT implode.
I have been fortunate enough to implode television CRTs for amusement, and the result is sadly not as exciting as might be hoped. It takes a hefty throw of a brick at the screen to make it break, and when it does there is just a mild pop and the glass drops on the ground. Very little to write home about. -
Not seeing loud bangs mentioned here.
Electrolytic capacitors can explode with some violence when reverse polarized. Don't be peering closely at them when they go off.
High voltage capacitors such as the ones used for xenon discharge tubes can make a loud bang if discharged accidentally through a short or a spark gap. Such once happened to me accidentally and I nearly jumped out of my seat. It is a bad idea to be close to anything hard or sharp when being startled like that. -
Congratulations on making it 40 years + without ever working with idiots.
If you're saying modern CRTs don't implode, there are about a dozen Youtube videos that would prove you wrong.
TV type CRTs have an implosion band/strap to help prevent it from happening. However, if you've ever worked on a maritime RADAR PPI display from before the raster scan era, you would know that the old round P7 phosphor tubes were very fragile. Same with certain high resolution P5 phosphor CRTs used in film recorders prior to the advent of Powerpoint and LCD projectors. Oscilloscope CRTs vary. It always seemed the more expensive the tube, the more fragile it is.
Now when it comes to safety, this attitude of "it can't happen" is exactly what gets people injured or killed. The chance of someone reading this and then working on an old scope or antique TV are quite high, so you are doing them a disservice by saying there is no hazard. I will agree that the odds are pretty slim; but they multiply rapidly in the presence of idiots and untrained personnel.
The point is, when you're working with this stuff, think ahead, be extra mindful of yourself and your surroundings, and don't take anything for granted. Think about the process before you loosen the first screw, for example, where are you going to set this thing down once you get it out of the case, so it doesn't slide off the table and hit the floor? You don't have to be frightened of a CRT, but it is best to have a healthy respect for them and treat them with extreme care.
In my experience there are only maybe two things more hazardous in the electronics field than a CRT: one is transmitter high voltage - particularly multi-kilowatt power amp B+ where if you're working with the interlocks disabled you need to keep one hand in your pocket, and the other is tower climbing. I have lost two friends from collapse due to structural failures on small towers on two separate occasions. Neither were professional climbers and in both cases it was not their own but a friend's tower that killed them.
I was going to mention the PPI CRTs,but considered it unlikely for beginners to come across them---perhaps incorrectly,but I have not seen anything similar available to the general public in my country since the late '50s,early '60s.
Enthusiasts used some of the early small & large electrostatically deflected tubes for home made TVs.prior to the availability of proper TV CRTs,& I remember seeing one very big old Brit radar tube fitted with a TV deflection yoke---don't know if it worked though.
Of course,a lot of these enthusiasts were ex military,& knew how to handle them.
I've handled most of the other tubes you refer to,but,as I said before,they are less hazardous because of their smaller size.
We used to chuck TV CRTs that weren't up to re-gunning into a big dumpster.
That very rarely broke the tube neck,so we would smash it with a long "star picket" or piece of pipe.
A gentle sigh,& that was it--no huge spread of glass.
We found some 12" tubes out of 1950s monitors,which did smash on impact ,but not a big bang--no glass flying.
You say," You don't have to be frightened of a CRT, but it is best to have a healthy respect for them and treat them with extreme care."
Reading your original posting in isolation would scare people off having anything to do with CRTs,or even small receiving tubes.
In order of hazards,I would put them well behind:-
Transmitter HT supplies,
Transmitter aerial interlock supplies----sometimes these are several hundred volts & are still present on the supposedly dead Transmitter--Ouch!-- That hurt!
3 ph Mains in all its forms
Single phase Mains
Switch mode supplies
Ladders
Ladders & Mains--nasty shock,nastier fall!
Lightning----I know,it is unlikely,but setting up an OB link on a hill & seeing a lightning strike about a hundred yards away persuaded me to delay the setting up for a while
All the towers I've climbed have been big ones that had been there for years & weren't going anywhere,but I remember a friend in the two-way radio side of things telling horror stories about small towers.
As a poor Ham,I've never been able to afford a proper tower.