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Definitely read the potential hazards section. Dangerous as hell these things.
by gumboza 4y ago
Definitely read the potential hazards section. Dangerous as hell these things.
- floren 4y agoDangerous to poke around inside when plugged in, but quite safe unplugged (unlike say an old TV).
- pyinstallwoes 4y agoWhy is an old tv unsafe?
- kenny11 4y agoThe CRT retains a high voltage charge even when the TV is unplugged.
- greenbit 4y agoThe CRT acts like a capacitor, storing charge for quite considerable lengths of time. Consider that a B&W would typically run 10kV to 15kV, and color sets easily 25kV, and that should give you some idea of how much energy one of those things can hold. And with those kinds of voltages, you don't even need to make contact to find you've become a discharge path, that stuff will reach out and grab you across considerable air gaps.
- dylan604 4y agooh, boy. the temptations of telling how to find out on your own are strong! the capacitors in CRTs could store a charge for a long time. i've seen people that assumed the caps were discharged find out the hard way when they shorted the leads with a tool. the noise alone is enough to make one need clean shorts. the only good thing is that they discharge quickly, but they give you "both barrels" worth to borrow a phrase.
- 1970-01-01 4y agoCRTs hold a deadly charge for minutes to hours after being unplugged. CRTs can also emit x-rays if you bypass safety circuits. And touching a live flyback would be shaking hands with death. They were also manufactured before RoHS, so don't lick the PCBs or throw them in the ocean. Other than that, they're perfectly safe.
- 123pie123 4y agoDO NOT ASSUME a CRT MONITOR or 'old' TV IS SAFE to poke around when unplugged!!!!!! https://www.instructables.com/How-to-take-apart-TV/ https://www.instructables.com/How-to-take-apart-TV/
- floren 4y agoRead what I wrote again carefully, paying extra attention to the word "unlike"
- 123pie123 4y ago"but quite safe unplugged" a CRT monitor is typically (I would not gamble on it - again!) not safe when unplugged
- dekhn 4y agoyes, you two are in agreement. it's the radio receiver that's safe when unplugged.
- gumboza 4y agoNot necessarily. The main filter caps can retain a high voltage depending on how it’s wired and if the designers installed a bleeder resistor and if the production guys didn’t remove it to save a few cents.
- II2II 4y agoUnlike means not like, so they were effectively saying it was safe to go inside radios but it is not safe to go into old televisions.
- 123pie123 4y agoappologies - I just re-read the article (and the other comments). I see where you're coming from I just saw the words "unplugged" and remembered the word vacuum tube - then massive emotions from my past came rushing through
- aidenn0 4y agoMy dad used to repair TVs; I asked him what the easiest way to discharge a tube was and he said "grab the anode lead and the chassis" then after I gave him a look he said "well you didn't ask for the easiest safe way to discharge one"
- userbinator 4y agoMany consumer appliances are also still unisolated inside, it saves cost and you are unlikely to be touching anything inside if you don't know what you're doing (hence the usual "do not open" warnings on them.)
- eternityforest 4y agoWith tubes you were much more likely to touch stuff inside though, since they didn't last forever and people used to fix stuff more.
- zhrvoj 4y agoYeah, do not attempt to use. High voltage inside. Better to buy any new low voltage piece of shit. Throw this all away. Be very afraid of this old stuff. Hmmm....your Tesla, runs on 3.7V LiIon...safe.
- II2II 4y agoIt is better to say that you should not go inside of an old television unless you know what you are doing, and don't assume that you know what you are doing unless you have guidance from someone who is experienced. Reading about or watching someone work inside of high voltage devices should not be considered sufficient since it is easy for either the author or reader to miss important details. It is also worth noting that electrical safety depends upon far more than voltage. We think of 3.7 V battery operated devices as safe because our bodies are not very good conductors (when dry) and some types of batteries have an internal resistance that will limit the current draw. If I recall correctly, the internal resistance of LiIon batteries is sufficiently low that they are dangerous if not handled correctly (e.g. if you short them).
- dylan604 4y agoSlap a "No user serviceable parts inside" sticker on it, and you have an unbeatable liability shield! /s
- jhallenworld 4y agoYeah, they are dangerous, but their safety can be improved: add polarized cord (probably have to move the power switch to the hot side for this) and replace the chassis ground capacitor. Table top FM radios and TVs also tend to be hot chassis.. (that mains transformer is just too expensive). Even today you can find capacitor dropper powered devices which are hot. AA5s are nice in that you can almost always get them to work for cheap. I mean if you have an older radio with a bad mains transformer, it's probably not worth fixing. Another advantage: they will work on 120V DC. I don't think low end hot chassis radios were popular in Europe, they all seem to have a transformer. Maybe 220V is just too dangerous... (but you can certainly have a primary to secondary fault in a transformer..)
- Aloha 4y ago240 was too high, and most of the non-110v sets use a transformer. In reality, the case is meant to isolate the set, so the thing is only relevant when performing service work, and honestly, I just measure voltage between chassis and earth and make sure there is zero volts of potential.
- gumboza 4y agoThat’s ok until you accidentally find you have an earth fault.
- Aloha 4y agoWell, in most cases I'm sitting on a chair isolated from earth, several feet in the air (wearing rubber soled shoes), so long as my test equipment shows 0v of potential to the chassis, its pretty safe. It could be that the earth bond has failed, but provided I have both pieces of gear sharing an earth, its all good.
- gumboza 4y agoFamous last words. Leave that scope probe ground clipped on something and every earth is floating live on your bench. Source: ex EE.
- Aloha 4y agoThey're perfectly safe to work on, just measure voltage between chassis and earth and make sure there is zero volts of potential - or be fancy and use an isolation transformer.
- gumboza 4y agoYou can still kill yourself with an isolation transformer fairly easily if you don’t know what you’re doing. See my other comments about earth assumptions.