TV out of focus - electronic gurus help!

[weaselnoze]

so my tv is out of focus.  if i remember correctly there should be a focus screw inside.  i've been shocked to hell by tv's before so how long do i have to wait for the power to drain before i go in and tinker?

[yamahonkawazuki]

so my tv is out of focus.  if i remember correctly there should be a focus screw inside.  i've been shocked to hell by tv's before so how long do i have to wait for the power to drain before i go in and tinker?

how old is this tv set?

[Onlypastrana199]

I have no idea about tv's but I took a power adapter apart from my computer recently, and it had been sitting since November and my dad came over and said hey whats this and poked at something with a screwdriver and it shocked him so bad his hand was numb for hours 

[RVertigo]

Capacitors can hold a charge as long as any standard battery...  And (I think) the tube holds a charge...

Is it THAT annoying?
Is it THAT nice of a TV?

Maybe it's just time to upgrade... 

[ajgs500]

I have no idea about tv's but I took a power adapter apart from my computer recently, and it had been sitting since November and my dad came over and said hey whats this and poked at something with a screwdriver and it shocked him so bad his hand was numb for hours

Your father also hurts himself killing mice.

[weaselnoze]

ah HA! i was very careful and took the thing apart.  well i was succesful of course!  i didnt touch anything that looked suspicious.  i turned the focus screw 1/4 turn CW and boy yah! i turned one man's trash into another man's 100 bucks!!! w00t im a tv repair guy now.

[Phaedrus]

 

Don't those capacitors store upwards of 30,000 volts? Haha.

I prefer to work with high discharge capacitors with wet spoons as my only tool! w00t.

Good job, Chris 

[Mandres]

You're lucky you didn't hurt yourself.  The tubes on most CRT (not flat-screen) tvs act as a giant capacitor and can hold a charge for a long time.  We're talking 20,000 volts here, enough to seriously hurt or kill.  The caps on the chassis can pack a wallop too, but it's the tube you really need to be careful of.  The big thick wire in the back of the tube (held in place by a suction cup) is the high-voltage line.  Don't ever touch that wire or cup until the tube has been properly discharged. 

-M

[12thmonkey]

And by "properly discharged" you mean "dropped off of a tall building," right?

[weaselnoze]

lol u guys.  i just might drop it off if no one wants it. 

[natedawg120]

And by "properly discharged" you mean "dropped off of a tall building," right?

I wanted to say something really dirty, use you rimaginations here, at the "properly discharged" part....  But yeah TV's shock the hell out of you, i know from experience.  I also however know that VCR capacitors can make for a fun office prank, falling off the roff sucks ( x 3), 89 jeep Comanchee + oil dipstick over pos term on battery sucks (x God I can't remember)......


Wait, i'm noticing a trend here 

[The Buddha]

TV's do have mecahnical focus as well as gun alignment ...
How hard is it going to be on a non projection set to get into and adjust it, as well as how likely is it to need it ... no clue ...
Cool.
Srinath.

[hmmmnz]

You're lucky you didn't hurt yourself.  The tubes on most CRT (not flat-screen) tvs act as a giant capacitor and can hold a charge for a long time.  We're talking 20,000 volts here, enough to seriously hurt or kill.  The caps on the chassis can pack a wallop too, but it's the tube you really need to be careful of.  The big thick wire in the back of the tube (held in place by a suction cup) is the high-voltage line.  Don't ever touch that wire or cup until the tube has been properly discharged. 

-M

although they are very high voltage, they have a very low current, its the current you have to worry about not the voltage,
you only need half an amp for half a second to kill you,
don't get me wrong if you got a belt of it it would friggin hurt

[weaselnoze]

i know it hurts! i've done it before thats why i was pretty cautious this time and was asking questions 

[calamari]

... its the current you have to worry about not the voltage,

you are right on that one... after all, I always get severe static shocks from 3000 volts (barely feel it) to 15,000 volts (hurts my finger/arm).

[3imo]

kudos on pointing out current kills not voltage.

My field of expertise is with Tactical air traffic control radars for the Army. I have been lurking inside these high votage panels for about 7 yrs now.

rub these two pennies together and see what you can do:

if you are working around something you suspect is holding a high voltage/current charge, keep one hand in your pocket.

Electricity usually kills by stopping your heart. electrons follow the path of least resistance. if you have one hand on the chassis (ground) and the other gets a current, the electrons will follow a path across your heart from arm to arm. effectively stopping your heart.

by keeping one hand in your pocket the current will likely travel down your leg, burning or even maiming, but your chances of survival are greater because the current will take the path of least resistance.

as far as TV's are concerned you will probably just recieve a slight momentary shoch, akin to an insect bite (to the tenth degree) simply because the short will likely occur across your skin. the path of travel being just were the contact points on the board are.
unless of course you dont have yur hand in your pocket and are touching a ground with the other hand effectively creating a circuit across your heart.

in that case I will put you up for a darwin award. 

[LimaXray]

You see the thing is, current does kill, but it doesn't take that much.  The limiting factor on if a device can kill you is how much current your body actually draws.  Because your body has such a high resistance, it takes a pretty high voltage to be able to draw enough current in order for you to be able to feel it or even die.   

The battery in your car is capable of sourcing tons and tons of current, but when you touch both the terminals you feel nothing.  This is because the Mega ohms of resistance through your body only draws a fraction of a mA at 12v.

Many high voltage sources, like the ignition system on your car, are not capable of sourcing more then a couple mA.  You will feel the shock because the higher voltage you can now draw a lot more current.  Fortunately you max out the capacity of the voltage source so it just kinda tingles.

Now some high power high voltage sources, like those in your microwave, are capable of sourcing only 0.5 amperes at a few thousand volts and will kill you INSTANTLY.

Basically, it order for something to be dangerous, you need a high enough voltage so that your body can actually draw the fatal current, and you need a source that can provide that fatal current.  Also note, high voltage power supplies with large capacitors are VERY dangerous, those capacitors store that current and can release a lot of energy through your body in a very short period of time.

On a side note, the reason we use 110v in the US when everyone else uses 220v is because of safety reasons.  You are a lot less likely to be harmed by a shock from 110v then by a shock from 220v for the same reason. 

[Mandres]

kudos on pointing out current kills not voltage.
as far as TV's are concerned you will probably just recieve a slight momentary shoch, akin to an insect bite (to the tenth degree) simply because the short will likely occur across your skin.

That is dangerously, potentially fatally, bad advice.  Beam current in the CRT is low, some tens of microamps. But the voltage across the tube is up around 25 KV. If you make yourself the conduction path for that voltage, the current will (briefly) be somewhat higher. CRT's do carry lethal charges. Like Leyden jars, the charge is stored as a strain in the glass, and so may be maintained for long periods of time.

If you need to mess with any CRT, get a long, skinny screwdriver and a clip lead. Attach the lead to the metal frame and to the screwdrive near the handle. Slide the tip under the boot on the side of the CRT where the HV goes in. Wiggle it in until you have contacted the metal HV leads, and then leave it for a couple of minutes.

I saw my uncle get bitten by a tube that had been improperly discharged.  I heard the zzzzap and saw his arm whip back fast enough to plant the screwdriver he was holding 2" deep into the solid wood paneling on the wall.  I've been careful with televisions ever since.

-M

[3imo]

kudos on pointing out current kills not voltage.
as far as TV's are concerned you will probably just recieve a slight momentary shoch, akin to an insect bite (to the tenth degree) simply because the short will likely occur across your skin.

That is dangerously, potentially fatally, bad advice. 
I saw my uncle get bitten by a tube that had been improperly discharged.  I heard the zzzzap and saw his arm whip back fast enough to plant the screwdriver he was holding 2" deep into the solid wood paneling on the wall.  I've been careful with televisions ever since.
-M

lets dance. 

what is bad about that advice? by "slight momentary" I meant time wise. when your uncle was bitten (like an insect bite to the tenth degree) it was a shock across a small area of his skin. a powerful zapp that caused his muscles to contract violently.

had his other hand been grounded his heart woulda stopped.  You woulda had to start that sentence with " I saw my late uncle...."

how does what I said conflict with what you said?  ~~~~3imo with his best, albiet weak, Masta P face starin you down~~~~

**Don't hate me Mandres. I only act tough cause I have a small pee pee, its kinda pathetic actually **

[LimaXray]

A shock from 20 some odd kV won't hurt you too bad if the current draw is low enough and you're not too well grounded.  I built a jacobs ladder (not the wooden block thing, but the mad scientist thing) that uses a ~22kV power supply and I've been shocked by it many times.  It's current limited to a couple mA, and while it will sure make my muscles spaz followed by me shouting a very enthusiastic "MOTHER F%&^#R",  it won't leave any serious damage.  But this is because I am only grounded by the air around me and I am very careful not to touch a better ground. 

The best way to minimize the shock is to be as poor of a path to ground as possible as 3imo said.  The better the ground you are, the more current you draw, the more power your body consumes, the more you cook, and the greater the likely hood your heart will fibrillate.  The advice 3imo gave about keeping your hand in your pocket is very true, and it's exactly what a text book would tell you.

But yeah, HV is awesome, if you're bored and need a new hobby it's good for hours of entertainment