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The Projects Forum Working on an electronics project and would like some suggestions, help or critiques? If you would like to comment or assist others with their projects, this is the place to do it.

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  #1  
Old 10-14-2006, 01:02 AM
BobJoe BobJoe is offline
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Lightbulb building a jacobs ladder

Hello,
I'm building a jocabs ladder. I have torn a tv apart already to get the transformer out of it, 26.4kv . Should I leave the transformer on the tv board, cut and tape off all the old wires off or completely remove the transformer? I''ll prolly end up looking for some 14-10 gauge wire to use and have random 2x4s floating around that I can use for bases.

Any thoughts or suggestions?
thanx
BobJoe

http://www.kronjaeger.com/hv/hv/exp/jacob/pt1_l.jpg
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Old 10-14-2006, 04:00 AM
BobJoe BobJoe is offline
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Does anyone know where the voltage ground is? Or where one could get the general schematics of an RCA tv board?
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Old 10-14-2006, 08:05 AM
Gadget Gadget is offline
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Most "Line Output Transformers LOP" (flyback transformers...FBT) out of any TV less than 15 years old or so, are of a Diode Split style, meaning there are built in diodes in the EHT winding, so the EHT output is around 28 - 30KV DC (as required by the Anode of the TV tube).
Older style TV's that used a separate "Tripler" unit to rectify and step up the voltage from the LOPtx dont use the built in diodes, so the output is normally around 8KV AC.
One side of the EHT winding is obviously the large rubber "Aquadag" connector, while the other is normally labled ABL.
The input winding normally has one end at the supply rail (112 to 140 volts depending on design) and the other end goes to the collector of a high power switching transistor working at the Horizontal frequency (15.625 kHz for PAL)... this is obviously going to be around the best frequency to use as it's what the transformer is designed for. A lower voltage could be used by winding your own turns on the transformer.... normally the turns ratio is less than one turn per volt. Needless to say, the voltages generated could be potentually lethal, and at the very least will cause a muscle reaction that will embed a screwdriver into the wall from 10 feet..(believe me).

A picture is worth a thousand words....
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Old 10-14-2006, 03:10 PM
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thingmaker3 thingmaker3 is offline
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Quote:
Originally Posted by BobJoe View Post
Does anyone know where the voltage ground is? Or where one could get the general schematics of an RCA tv board?
What model?
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Old 10-14-2006, 03:33 PM
BobJoe BobJoe is offline
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Hey:
the weird this is that schematic almost makes sense to me, not completely but... is the model written on the board or will i need to dig the tube out of the garbage?

thanx for the warning of the high voltage being lethal. i was aware of that, but still need to get the burried into my head. im thinking about getting some plexy glass and making a case around the ladder so no one accidentally touches it after its completed.

thanx so far and ill try and find that model info
BobJoe
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Old 10-14-2006, 05:07 PM
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beenthere beenthere is offline
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Hi,

Shielding around a Jacob's ladder is always a good idea. Not only do you not get zapped, but stray breezes don't blow out the arc and ruin the effect. Check out the movie "Frankenstein" or "Young Frankenstein" (uses the props from the original) to see how it was done.

Sparks transmit energy all over the RF spectrum. You could get to be real unpopular if yours kills wireless phone and cell reception. Broadcast radio will also get affected. Invite the neighbors to see the show and don't run it all evening.
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Old 10-14-2006, 06:06 PM
BobJoe BobJoe is offline
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hey,
Thankx for the heads up on the RF thing, I was unaware of that.

Anyways, everything is under loads of garbage other than the board and that says it's a 3400 area keyboard, I think thats the info for it?

BobJoe
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Old 10-16-2006, 02:20 AM
Ian01 Ian01 is offline
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I don't know if you know this already, but the transformer in the TV is a flyback transformer. It's controlled by the TV's flyback circuitry, and will not work without it.
http://en.wikipedia.org/wiki/Flyback_transformer
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  #9  
Old 10-20-2006, 01:08 AM
EEMajor EEMajor is offline
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You can use a flyback in apps such as this, with some simple mods, check out this link:

http://www.aaroncake.net/circuits/hvgen.htm

Also, this link: http://www.angelfire.com/80s/sixmhz/flyback.html

A google search will turn up multitudes of drivers and simple mods for use with flybacks..... Great small HV source. Now if you really want to have fun, go to your local neon sign company and buy an old used neon sign transformer (The large ones, not the small dinky ones) for about $50.00! Those make a fun Jacobs ladder. I'll take some pics and post them when I pull it out for Halloween!
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Last edited by EEMajor; 10-20-2006 at 01:12 AM. Reason: Adding information and another link
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  #10  
Old 10-21-2006, 12:15 AM
BobJoe BobJoe is offline
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OH sweet!!! I can't wait to see pictures of your Jaboc's ladder.

I still have to look into this flyback thing. Then I'll have to figure something out.

I don't think anyone seriously believes that I plan on having this fully built and going.
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