Discharging of HV in TV's

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Discharging of HV in TV's Empty Discharging of HV in TV's

Post by tuberadiogeek on Fri Apr 26, 2013 5:15 pm

I just picked up 2 older tvs off my neighbors curb last night, he hollered at me last night and told me about them so i nabbed them. Well after inspecting them theyre pretty much junk. One turns on with a super dark picture and the other one jumps channels and wont go to 3 or the A/V's so i could try a cable box or VCR. I tried progamming a universal remote but all 11 codes wouldnt work at all. It has a built in VCR, and upon putting a tape in it will show you hit play but powers off the tv right after. So, i want to open them up and try to retrieve as much copper as i can out of them, but dont want to get knocked on my arse by high voltage. How long do they need to stay unplugged before it is safe for me to tear into them? One was plugged in about 5 minutes and the other about an hour. Both 19" models, one from 1989 and one from 1996.
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Post by Bill Cahill on Fri Apr 26, 2013 8:29 pm

Thesenewer sets seem to hold their hv forever. The capacitor coating is alot heavier, and, holds alot more hv. Alot of the sets warn against trying to discharge hv to ground as it will blow out many parts.
You could try disconnecting key parts, and, discharging several times to the picture tube ground strap.
Warning, depending on size of set, they use an awful high voltage.
Could be as high as 40,00 volts on a 27" set.
There isn't much copper in these, either, They use alot of aluminum, plastic, and, aluminum paited plastic. Very little copper.
Bill Cahill
Oh. and, they don't tend to have a power transformer, most run off the line.

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Post by tuberadiogeek on Fri Apr 26, 2013 8:59 pm

That is what i was afraid of.. I know they can have ALOT of voltage, that is why i was asking.. I was thinking there would be chokes on the CRT that would be wrapped in copper. I guess i will remove the back off the 1989 model carefully and see if there is enough copper to make me want to tear into it. I'm guessing i'm going to find a power board with large caps on it?
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Post by Bill Cahill on Fri Apr 26, 2013 9:06 pm

Yes, and, a board on the picture tube with two terminals, at least, with high voltage for the focus.
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Post by terrydec on Fri Apr 26, 2013 11:45 pm

Use a large flat screwdriver and a wire with a clip on each end. Clip one end to a good solid ground on the chassis. Clip the other to the screwdriver. Carefully slide the screwdriver under the rubber cup until it contacts the HV lead. When you hear the 'snap' you're good to go. If you want you can touch some other points in the power supply but it isn't necessary. Power Supply caps discharge pretty quick.
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Post by Guest on Sat Apr 27, 2013 12:09 am

Power Supply caps discharge pretty quick.

Power supply caps are filters and will dischage quickly if the bleeder resistor is good. A defective, disconnected or missing bleeder resistor can cause you to get zapped!

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Post by Bill Cahill on Sat Apr 27, 2013 12:15 am

Actually, I've seen the main high voltage filter remain charged because the power supply supplies voltage to the computer.
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Post by tuberadiogeek on Sat Apr 27, 2013 12:27 am

Well, lets hope that resistor is good. As i do not feel like getting hit with a couple thousand volts.. 120 volts is more then enough for me.. As stated above i do not know much of anything about these TV's besides they do not operate properly.
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Post by Bill Cahill on Sat Apr 27, 2013 9:18 am

Please handle with kit golves. Even if the resistor is there, and, good, it doesn't discharge the hv. Only the B+.
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Post by Dr. Radio on Sat Apr 27, 2013 9:24 pm

IMHO (in my humble opinion), I think the original poster should just leave these tv's be. If he is not comfortable/experienced with tvs (which it sounds like he isn't, and I don't mean that in a mean way), the risk greatly outweighs the small amount of useable parts.

There really isn't a lot (weight wise) of copper. The vast majority of parts have served their duty and are old and tired.

Some CRT's are designed for 50,000 volt operation, and a good CRT (cathode ray tube) can effectively hold a charge for years. Discharging (completely) can be a bit un-nerving even for those familiar with the proceedure. Ultor, quadag, ground all key terms here.

Those new of tv's would use switch mode power supplies, so, yes, you'd need to use caution on the typical storage/filter capacitors as well. "Hoping" safety mechanism are present or still functional is risky business.

Just my 2 cents, don't want to see anyone get hurt.
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Post by tuberadiogeek on Sat Apr 27, 2013 9:37 pm

Well like i said, i'd like to remove the back off of one, probably the 1989 one since it looks like its easier to get the back off and take a look to see if there is enough copper to mess with. If not then i will cut the cords off to re-use them and put them back on the curb for the next garbage run. Like i also said i'm not wanting to get knocked on my arse by a couple-few thousand volts.. bc i know its dangerous and will hurt. Ive been hit by what i believe to be a service drop years ago when i was a kid and i dont want to experience similar results again.. plus that is why i asked here before i did it..
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Post by willy3486 on Sat Apr 27, 2013 10:57 pm

Here is what I do to them. I take the back off and get a couple jumper wires with alligator clips on them. I clip one to a flat screwdriver and the other end to the to a ground on the TV. I then take the screwdriver and put it under the HV clip to the tube to discharge it. I also use the screwdriver to pop the cap off the tube. I then take insulated pliers and grasp the wire of the cap and touch the metal in the cap to the metal ground of the TV if I can reach it. I then unscrew the chassis and take it out.

The two good pieces that have copper is the yoke and the degaussing coil. I take them out and then put the back on. I keep the chassis for parts then scrap the copper. I put the back of the TV back on and send that TV cabinet to the recycler. I get probably get anywhere from two to four bucks for the scrap I can recycle off each TV on the average. Doesn't sound like much but it usually take me about five to ten minutes at the most to strip one. The newer ones switched from Copper on the degausing coil to Aluminum so check it first.

I found out a long time ago to recycle it all. Its a little work to do but it cam make you some cash. Later on I plan to make a wire stripper that will crush the plastic. I have read that you can use two armatures,one driven by a motor and the other on a frame on top of the other armature pressing down. I think I have found all the parts I need so I just need to find the time to do it. The reason I want to make one is I have enough copper wire like cat 5,telephone, and electrical cords to almost fill a 55 gallon drum if it was all stripped. Think about how many radios I can buy with that cash.

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Post by terrydec on Sun Apr 28, 2013 12:20 am

This is pretty much exactly what I said in my post-

willy3486 wrote:Here is what I do to them. I take the back off and get a couple jumper wires with alligator clips on them. I clip one to a flat screwdriver and the other end to the to a ground on the TV. I then take the screwdriver and put it under the HV clip to the tube to discharge it.

The clip itself is like a hairpin, so it takes a pair of needle nose pliers to pinch it together. The biggest problem is getting under that thick rubber cup.

I've worked on a LOT of TV's and haven't zapped myself yet. I've worked on some when I was pretty zapped though. (joke)
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Post by Bill Cahill on Sun Apr 28, 2013 12:23 am

Did I ever tell of when I launched myself accross our basement on the family tv??
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Boy, was I stupid!

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Post by terrydec on Sun Apr 28, 2013 1:07 am

I fixed up a B/W TV I had found in the alley- This was years and years ago. I finally got it going but I'd left the back off with specific instructions not to touch anything. My wife did, of course. Apparently she shot across the room. My 4 year old son figured out how to call 911. Good kid. When I got home I saw the emergency vehicles just leaving, and the TV out in the alley again, with a smashed picture tube. I only had to sleep on the couch for a week.
And I found out that I sometimes do REALLY stupid things. I'm better now, but of course divorced.
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Post by 75X11 on Sun Apr 28, 2013 2:04 pm

I always thought the horizontal flyback transformer was an aptly named component. Razz
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Post by terrydec on Sun Apr 28, 2013 3:15 pm

75X11 wrote:I always thought the horizontal flyback transformer was an aptly named component. Razz
Yep, if you touch one you're gonna fly back alright. affraid
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Post by scottb on Sun Apr 28, 2013 3:36 pm

I was working in a tv shop early 80's to help pay for college. I saw the best tech touch a powered up horizontal output transistor te see if it was running hot. Thing was he was on heavy cancer drugs so probably was not thinking right. Although I do not recommend it, he was cancer free a month after that!!!!

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Post by terrydec on Sun Apr 28, 2013 3:44 pm

Now THAT is what I call Re-Mission. cheers
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Post by Bill Cahill on Sun Apr 28, 2013 5:51 pm

Yeh. The hard way...'
Now, let me tell you this true story....
First, a little back ground history.
In the basement, the wall facing our side walk side of the house, under what was once Our sister's bedroom, on the wood wall, was a burned spot where 10 years earlier the family tv was put by my mother. One day at that time the original power cord shorted out, and, caught fire. No, it didn't blow the fuse, ehter. It was really arcing badly, sparks flying everywhere!
My aunt that was staying with us at the time saved the day by unplugging the set before it burned down the house.
Now, flash forward ten years later.
Same set, different chassis.
I was trying to get the set playing again. I had had my new job at the tv repair shop for a whole week!
Well, I got the picture tube to develop a raster. I was excited. I diidn't get it playing, but, had high voltage, and, a bright raster.
It was my day off from work. I called the shop to ask for any ideas. My Boss, the owner, reccommended I try the tuner tubes.
I unplugged the set.
I was stupidly standing in my bare feet on linoleum on a cement floor in the basement.
Well, I was holding a big old desk lamp in my left hand.
I put my hand in set, and, headed for the tuner, which on this set is right next to the metal bell of the picture tube, and, that bell gets the 13,000 volts of high voltage.
Well, my little pinky of my right hand, accidentally touched the metal bell of the tube.
Instantly, I felt a very strong jolt shoot up my right arm, accross my back, down my left arm, and, into my left hand.
All I remember is letting out a scream, and, I went flying through the air.
The lamp landed unplugged in another spot of the basement.
I landed smack dab, exactly on the spot where years earlier the tv cord had caught on fire.
When my head hit the wall, I was knocked out.
Not sure how long I was out, but, when I came to I shook my head.
I looked to see where I was. Ijumped up in fright when I found out where I was.
I gathered up the lamp, and, plugged it in. Whew! It still worked.
I called the shop to tell them what had happenned.
I got the other shop tech, Gene Petuna. Craig was on a service call.
I told him what had happenned. He burst out laughing.
He said, "you dummy! You should have discharged the high voltage first." I asked how to do that, and, he gave me the proper instructions on how.
I asked him if I should do that now. He burst out laughing, and, said, "Heck NO! You already have!"
Bill Cahill Shocked

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Post by 75X11 on Sun Apr 28, 2013 7:17 pm

You were lucky to live to get the benefit of that safety lesson! I don't think I would get any enjoyment from working on TVs. Old radios are about as electronically violent as I can stand. pale
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Post by Bill Cahill on Sun Apr 28, 2013 9:18 pm

Take the right precautions, and, t'v's are samfe tp work on......
True, much higher voltages, but, imagine the thrill you get when you get them playing again.
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Post by terrydec on Mon Apr 29, 2013 12:21 am

The best way to discharge the high voltage in a TV is to send a cat inside. If the cat lives you can start work. cat
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Post by 75X11 on Mon Apr 29, 2013 12:31 am

And then it will stand back and watch the fireworks begin! Very Happy
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Post by terrydec on Mon Apr 29, 2013 1:24 pm

My cat is trained for this sort of thing-

Discharging of HV in TV's Hang_in_there_poster-r6e81a8f84aa043cfa9ed4b7ebae1a5af_wfb_152

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