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Mmmm . . . yeah. I think I'll leave this sort of stuff to the pros.Originally Posted by martinsantos
Just a little advice... Take a lot of care when opening any of these old Tv sets. Them use a lot oh HIGH VOLTAGE components. Some very early Tv tube got voltages as high as 27.000 Volts. Capacitors can storage eletricity for several years, sometimes several decades, ever if never turned on again.
Mmmm . . . yeah. I think I'll leave this sort of stuff to the pros.
"Hello. I'm Mr. Hardy, and this is my friend, Mr. Laurel."
The voltage sounds scarier than it actually is. Postwar television sets had high voltage on the picture tube anode, but it was very low current. It won't kill you, but it'll give you an awful jarring, perhaps enough to drop the set on your foot, which will hurt even more than the shock.
Prewar television sets, on the other hand, and one or two cheap off-brand postwar models, used step-up transformers to generate their high voltage off the power line, and these *will* kill you if you touch the wrong point. Best to leave these sets to professionals.
Aside from the picture tube circuit, there's the usual 350 volts or so of DC that you find in any vacuum-tube equipment, radio, television, or whatever. The current is low enought that this won't kill you either, but it'll knock you across the room if you get bitten by it, and your arm will be numb for a week.
The humblest citizen in all the land, when clad in the armor of a righteous cause, is stronger than all the hosts of error. -- William Jennings Bryan
Of course the picture tube is the very high voltage (I wrote "Tv tube"); usually tubes works from 150 to 300V/DC. Saw once a high-end audio amplifier with almost 700V in the top of a pair of 6SN7, but this is the exception.
But what I think scary about these Tv sets is that usually they are off for a long time. A cord can be broken inside, etc, so when you touch a usually "safe" point you can get a full high voltage.
I got once a shock of around 300/350V directly from the power transformer of a radio. It hurts!(the radio was on because I was tracking the signal).
I think the biggest danger is with the capacitors. Even with the set off, the eletricity is there. And is a quick and strong discharge - and I think the amperage here isn't small as when the set is on. My RCA Tube Manual says to "disconect" all very high voltage capacitors (and to short-circuitry to ground the high voltage ones) before working with a Tv set.
The easy way to deal with that is take a heavy screwdriver, solder a piece of anode lead to it, and an alligator clip to the end of that, and clip it to the chassis. And then touch the positive terminal of each cap with the screwdriver to draw off any remaining charge. Do this until it stops sparking, and you should be fine.
Don't forget to do this to the anode terminal on the picture tube, too -- that's where the biggest charge will be found.
The humblest citizen in all the land, when clad in the armor of a righteous cause, is stronger than all the hosts of error. -- William Jennings Bryan
Don't use a tang thru screwdriver........
I have my Grandmother's Dumont RA-112 that she bought in Dec. 1949. (Still has all of the papers, and the power cord tag)
It's quite interesting with the continuous radio type tuner and green cat's eye on the dial.
I lucked into a full Dumont factory TV shop binder with all their schematics, and repair bulletins.
It would be cool if you could pull in (from outer space somewhere) some of the old Dumont shows, like good old Captain Video, and the original season of Your Show of Shows.
"Hello. I'm Mr. Hardy, and this is my friend, Mr. Laurel."
In a little book about electronics, from 1932, a schematic of a Tv set. No picture tube, but a disc with lens and lamps and a motor.
I would love to see the results of anyone who tried to make a Tv in those days... (probably it won't work today because the number os lines, etc).
You'll want to visit here:
http://www.televisionexperimenters.com/
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