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[rarborman]

maybe a insulated grounded (outlet ground) cord with a metal conductive pin... but how do you dischange them?

[Patchouli]

CRT stands for "cathode ray tube."


Patchy, that sounds sensible, but how do you suggest discharging the high voltage components?  There's still going to be a pathway, well, through your body, just not through your body and off to the ground.

Discharging a capacitor can be done by directly shorting out the two terminals with a wire, but that's not safe at all in situations where you have a capacitor storing large amounts of energy. It will make sparks if you do this. Look up discharging capacitors on youtube. Safely discharging a capacitor requires a resistor.

Current will follow the path of least resistance, so I think you'd want to do all you could to increase your resistance or get as close as you can to an open circuit by using an insulator, until the capacitors are discharged. You'd ground yourself for voltage-sensitive components, but for high-voltage things, safety is the better way to go.

But I still think it's a terrible idea to mess around with it if you don't know what you're doing. I don't even know what I'm really doing. For some perspective, 0.1A is lethal.

[Starver]

Can I add that I think you need to put things back together.  I wouldn't care to try to repair a TV[1], and I already knew the answers to the following:

ok, what does a capasitor look like? and what does it do?

Whats CRT mean? and how do you discharge stuff? and how do I know if a compacitor is broken or not?

That I'm pointing out that you're asking these questions is not an insult to you (indeed, you are asking), but even if we do give you enough information to correct your former lack of knowledge I wouldn't count that as a new-found capability to do the work you're asking for.

It's not just another step up from making a temporary repair to a low-power charger cable.  Seriously.



The details as such in the footnotes are a 'summary' of what knowledge I could provide, but I wouldn't want to take that mish-mash of advice from anyone if I was starting out.  Not sure I'd even take it from myself, at the better-than-amateur-less-than-completely-competent level that I probably am at, and someone who is above me in experience level can probably give you several good reasons why ignoring me and just keeping out of it would ultimately be the wisest course of action.  But it's there, anyway.




[1] I've poked around (fairly literally, but not entirely as carefree as it sounds) inside 'broken' ones which I was never going to actually repair.  The dangerous bits are connected to the tube (this of course being applicable to the old-style non-flatscreen TVs) and the board (usually connected to obvious bare copper coils, and by particularly thick but insulated wires) or part of the main-board, if all-in-one, that generates the deadlier degrees of currents.  Earthing oneself is good, but if you're going into this area you also need an earth-connected probe of some kind (edit: Oh yeah, resistors are good for bridging capacitors, but make sure you have less resistance to earth than you'd provide, still...  not sure what my own resistor bands are, how many Ohms is the typical human body? ) to make prior contact with whatever you're likely to touch or work near to, to let it discharge.  (Bad description that, but earthing oneself on one hand and touching such things with the other certainly isn't a good idea.  Also, some components retain charge for a long time, so leaving it unpowered for a day or more is not something you should rely upon.)

The next most dangerous circuit is the mains-receiving bit, usually the worst bit in any other electrical product, although obviously (right?) you're not going to be messing about with any mains switched on (plugged in for earthing purposes is useful, but make sure there's no chance of the power being switched on by yourself/inquisitive others unless you know you need it on.)

Down at the bottom end (although may still be dangerous if either in close proximity to the above two sub-boards or all contained on the same single (or main) circuit board as the above) are the sub-circuits responsible for tuning, for receiving the IR signal from the remote, teletext/whatever decoding and the like.  It's possible you can disconnect those, given them the necessary power rating from a benchtop PSU (or, if you're looking at the right volts/amps, the relevant rails supply of a PC PSU[2] and check their functionality with suitable measuring instruments.  But it depends on the problem.

If it's just the power switch that's broken, then you may be able to desolder the original and get a suitable match soldered back in again.  But I honestly wouldn't go into anything more complicated.  Beyond that (and identifying obviously blown capacitors, but with the warning on handling/working near the ones with the high voltages in them) it's analogue waveforms and digital pulses and I don't think you have the equipment to work it out from scratch.  And I wouldn't care to do so on anything other than a throwaway piece of equipment, still.  Actually fixing might be simple, but I'd still prefer an electronic professional with experience to handle that sort of thing.

[2] Having made the green-to-black connection to signal a "power up" requirement, of course.

[Patchouli]

^ I agree.

Assuming the buzzing is more than the ambient sort of buzz that's typical of electronics, I would recommend returning the TV and recommending the client to another person.

[MonkeyHead]

DO NOT PLAY WITH THE POWER SUPPLY/POWERBOARD FOR A MAINS DEVICE UNLESS YOU KNOW WHAT YOU ARE DOING.

MOST CAPACITORS HAVE A CARCINOGENIC DIELECTRIC, AND DONT RESPOND WELL TO HEAT. DONT SOLDER THEM WITHOUT SERIOUS HEAT SINKING.

Most probably the buzzing is in the power supply - these are often built around a transformer, which uses the AC supply to create an oscilatory B-field, inducing a more suitable secondary voltage to run the TV. Over time the windings or core/laimnated plates of the transformer can come slightly loose and "rattle" a tad at about 50 to 60 Hz depending on your local supply. Its really no big deal, but can be a sign that you might want a new TV. A new power supply is often far more costly than the cost of a new TV.

I had an old TV where rain water tracked down the internal section of the ariel cable into the power supply. 230V AC was arcing inside the casing, damaging many components. I took it apart and had a look myself, and even though I have abundant experience in electrcial stuff and habitually repair many different things decided to play it safe and pay the 60 quid to get it fixed by someone who knew what they were doing - despite knowing what the main problems were. It simply wasnt worth the risk.

[MarcAFK]

I seem to recall seeing someone discharging capacitors by merely shorting them with a screwdriver, but that was with lower voltages, you get a spark, obviously with a 240 volt high capacity capacitor you would get a large possibly blinding spark, you could weld the screwdriver to the capacitor and theres a possibility of something exploding/popping if you do that (either the capacitor or the screwdriver)  Don't just take my word for this, but i believe you're supposed to use a jumper that has a largish resistor wired into it of the right voltage as your capacitor, connect one end to ground (earth?) then touch the jumper to the positive pin of your capacitor. Note, you could still kill yourself just as easily with this jumper if you hold it or earth in one hand and touch positive with the other hand.
EDIT: Significantly obsolete Information, somehow i missed page 2 of this post so whatever anyone said above this is probably more accurate.

[G-Flex]

ok, what does a capasitor look like? and what does it do?

Whats CRT mean? and how do you discharge stuff? and how do I know if a compacitor is broken or not?

I'm going to say this right now: If you don't know what a capacitor is, don't attempt to fix electronics or tell people you can. If you don't know what "CRT" means, especially don't attempt to fix a television.

I'm going to say this again, in larger type, so you know damn well how serious this is.

If you don't know what a capacitor is, don't attempt to fix electronics or tell people you can. If you don't know what "CRT" means, especially don't attempt to fix a television. There is a good chance you will either destroy valuable equipment, ruin other people's stuff, or seriously injure yourself.

Not only are you getting in over your head, you're likely to cause serious damage to property or yourself. You are playing with valuable and dangerous equipment, not lego blocks. You can't just do dangerous shit like this despite not knowing what you're doing. Instead of pretending you know how to repair electronics, I suggest not getting yourself killed, and actually learn about them instead. You aren't some kind of magical wunderkind who can safely and effectively work on electronics despite knowing nothing about them just because you looked up a couple DIY manuals. Learn what you're actually dealing with first, then think about applying that knowledge.

[dragginmaster]

ok, what does a capasitor look like? and what does it do?

Whats CRT mean? and how do you discharge stuff? and how do I know if a compacitor is broken or not?

I'm going to say this right now: If you don't know what a capacitor is, don't attempt to fix electronics or tell people you can. If you don't know what "CRT" means, especially don't attempt to fix a television.

I'm going to say this again, in larger type, so you know damn well how serious this is.

If you don't know what a capacitor is, don't attempt to fix electronics or tell people you can. If you don't know what "CRT" means, especially don't attempt to fix a television. There is a good chance you will either destroy valuable equipment, ruin other people's stuff, or seriously injure yourself.

Not only are you getting in over your head, you're likely to cause serious damage to property or yourself. You are playing with valuable and dangerous equipment, not lego blocks. You can't just do dangerous shit like this despite not knowing what you're doing. Instead of pretending you know how to repair electronics, I suggest not getting yourself killed, and actually learn about them instead. You aren't some kind of magical wunderkind who can safely and effectively work on electronics despite knowing nothing about them just because you looked up a couple DIY manuals. Learn what you're actually dealing with first, then think about applying that knowledge.

I second that, or third fourth and fifth it with extreme predjudice.

Owning a soldering iron does not imbue the owner with electronics knowledge. If you cannot identify simple electronics components, or know enough about TVs/monitors to know what CRT means, your "looking at it" should never have even allowed you to remove the screws holding the exterior case together.

[eerr]

I don't fuss with electronics, because they have phosphorus, and heavy metals inside.
I can feel that shit workin on my hands.

Maybe the library will have a book on appliances or Tv repair?