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Registered Member #1790
Joined: Fri Oct 31 2008, 10:10AM
Location: Sydney, Australia
Posts: 40
Hi everyone,
Well I have thought about it and have made up my mind to make a homewound ferrite transformer that puts out 600 -800 volts at 240 milliamps, it will be wound on old flyback core and I will drive it with a half bridge of Irf740's.
For the fillaments I will make a small 6.3 volt linear power supply that is able to source approx... 5 amps of current, although the tube itself requiers much less (0.7A I think it was), I like having a saftey margin.
The schematic im going to use is this one , which is a dual 811 vttc, I will use it because of the simialrities between the two tubes and it seems very simple.
The reason i'm not going to use a mot is because its going to be excesively heavy and is also very dangerous, I dont really want to push those tubes, I just want to make a reliable first vttc.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
The reason i'm not going to use a mot is because its going to be excesively heavy and is also very dangerous, I dont really want to push those tubes, I just want to make a reliable first vttc.
Good idea :). That schematic is what i use on my 811a vttc and i have used it on two small horizontal output tubes from televisions. It works great, and the first time you put it together, it will work.
If it does not work be sure that everything is good(like the resistors and cap) and the primary and feedback must be connected right or it will not oscillate. It will not work properly or at all if your secondary has a broken wire and if it has shorted turns, the turn will heat up badly and melt the former, and eat all the power. It would also heat the tube up badly.
Registered Member #1790
Joined: Fri Oct 31 2008, 10:10AM
Location: Sydney, Australia
Posts: 40
Steve McConner wrote ...
If you want it to be reliable, why on earth are you introducing the extra complexity of a switchmode power supply?
You could build a SSTC with the same components, and it would be more reliable because you got rid of the tube.
Steve by reliable I mean the tubes being safe from over voltage , not how complex a swithcher is going to be, I honestly wouldnt mind making a psu for the coil as I like having something to do, when im bored (especially when I have a month of holidays coming up ).
How ever I do understand what you mean, building a hv smps is very complicated so there is more chance of something to go wrong especialy when its working around such an environment.
But I see it as very rewarding as it makes your coil alot lighter and the transformer is not as dangerous as an MOT.
However I may first rewind an old transformer to give me 600-800 volts at required current an than if everything is ok I can go ahead and work on smps
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Information on 807 tubes
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