electrostatic deflection idea

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electrostatic deflection idea

Postby Harry Dalek » Fri Mar 20, 2015 9:54 pm

I am sure its been done and found some thing along the lines on you tube about using electrostatic deflection on a magnetic deflected crt .

I was going to ask Steve if it was possible.

I was thinking if you made a yoke of plates that fitted on the outside of the narrower magnetic type CRT would it work ?.

Have nothing handy to do a test but looking at this fellows rather ruff go at it with batteries it seems to .
i am not sure how this is working as in electrical connections i would be thinking if its doing what hes says one end of the battery is to earth other wise i would say the beam is attracted to the metal which is the same sort of idea any way or may be its just working as he says i don't know but it is an interesting idea .

https://www.youtube.com/watch?v=RwrQ-kundMw&spfreload=1
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Re: electrostatic deflection idea

Postby Steve Anderson » Fri Mar 20, 2015 10:38 pm

Harry Dalek wrote:...but looking at this fellows rather ruff go at it.

"Ruff"? I'm sorry, but why post something so crappy? Not you Harry, but whoever this guy is. Good idea - but do it again. Geez. Even with something as crud Windoze Movie Maker that could have been re-done and tidied up. I'm not looking for a Hollywood production, but please! It's unwatchable (if there's such a word). I watched maybe 30% of it and gave up.

Anyway, there must be a reason why this hasn't been done or at least I've not seen any reference to 'External Electrostatic Deflection' before.

Two things spring to mind - with the wider separation of the external deflection plates the sensitivity will be less and the intervening glass and air could nullify the charge effect on the electrons. I'll have to go back to some basics (reference books) when I get back home.

I vaguely recall the glow of a Crooke's Tube could be deflected by an external electrostatic field...but it is vague!

Steve A.
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Re: electrostatic deflection idea

Postby Harry Dalek » Sat Mar 21, 2015 4:19 pm

Yes Steve sorry about that best i could find doing a you tube test on the subject a lot of fast forwarding i wanted to see the experiment not the camera movement noise .

I would say he needs to get to the point of the video . I also see he has made or making a electostatic yoke for it i would have like to have seen more of this .

As far as its possible the glass must have some effect but i found yet another wonderful video on the idea ,does DC voltage pass through glass and it does so i would think it now is possible to move those electrons.

Sorry about the music least its not camera noise !

https://www.youtube.com/watch?v=8czuq3dOJgk
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Re: electrostatic deflection idea

Postby Panrock » Sun Mar 22, 2015 2:17 am

Harry, I can't see why the electrostatic influence shouldn't work through glass - in principle at least. I once wrapped a 3-inch VCR139A tube with kitchen foil (except at the screen) and I forget, either earthed it or connected it to +EHT (much the same thing with a 'high negative cathode' driving arrangement). This neatly removed the 'screen charge repulsion effect' that you sometimes get in non-aluminised tubes. This effect causes the raster to grow slowly within a distorted boundary when first switching on.

However for deflection, I think it will be difficult to obtain a sufficiently intense field gradient, bearing in mind the much greater electrode spacings outside the glass. Also, if the external electrodes are curved and wrap round the neck, that could cause raster distortion problems.

Easier to stick to the "magnetics"! :D

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Re: electrostatic deflection idea

Postby Harry Dalek » Sun Mar 22, 2015 8:28 am

Panrock wrote:Harry, I can't see why the electrostatic influence shouldn't work through glass - in principle at least. I once wrapped a 3-inch VCR139A tube with kitchen foil (except at the screen) and I forget, either earthed it or connected it to +EHT (much the same thing with a 'high negative cathode' driving arrangement). This neatly removed the 'screen charge repulsion effect' that you sometimes get in non-aluminised tubes. This effect causes the raster to grow slowly within a distorted boundary when first switching on.

However for deflection, I think it will be difficult to obtain a sufficiently intense field gradient, bearing in mind the much greater electrode spacings outside the glass. Also, if the external electrodes are curved and wrap round the neck, that could cause raster distortion problems.

Easier to stick to the "magnetics"! :D

Steve O


Thanks Steve interesting reading of your experiment ,i was thinking it must of been tried in the past .
Yes again if you have a magnetic type yoke in the first place no need to replace it with a bad idea ,if you had nothing then thats another story ... :wink:
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: electrostatic deflection idea

Postby dominicbeesley » Tue May 26, 2015 11:40 pm

I mucked around with something like this a while back - I was trying to get spot wobble on a magnetically deflected black and white CRT and tried making a 3MHz oscillator and putting some small plates either side of the neck...I did sort of get the spot to move around but it also screwed up the focus. Getting it to work on the wider part of the tube might work but then you'd need to clear off any dag coating and use very high voltages I suspect.

I also tried it on a colour tube and got some very funny looking results!

D
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Re: electrostatic deflection idea

Postby Harry Dalek » Wed May 27, 2015 4:11 pm

dominicbeesley wrote:I mucked around with something like this a while back - I was trying to get spot wobble on a magnetically deflected black and white CRT and tried making a 3MHz oscillator and putting some small plates either side of the neck...I did sort of get the spot to move around but it also screwed up the focus. Getting it to work on the wider part of the tube might work but then you'd need to clear off any dag coating and use very high voltages I suspect.

I also tried it on a colour tube and got some very funny looking results!

D


HI Dom

That is interesting i was thinking the idea might work to some degree ... good to hear of your try ...
Your experiment sounds to me like the plates would have to mimic the shape of a magnatic yoke coils as it bends to the shape of the crt past the neck .
With the High voltage to the plates you would try it on a small tube to keep that down...i suppose its not an efficient way to do this or they would been tvs with this idea .
BTW reading past post of yours from a few years back ....did you ever try your vidicons ,i was reading the comments and seemed like it was like don't bother its to hard ...mainly because you had no deflection coils and or focus coil .
I was thinking picked the wrong person to put off coil winding :wink: Any case you should check out Troys work on vidicons and iconoscope.
This fellows work is amazing as well and he did the lot ! https://www.youtube.com/watch?v=UEoxVHxAapA
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Re: electrostatic deflection idea

Postby dominicbeesley » Wed May 27, 2015 10:51 pm

Thanks Harry,

I used fairly small plates on the neck of the tube just after the gun assembly. I didn't try on the wider part of the neck as I had the deflection coils working as well as trying electrostatic, also the tubes were coated with conducting DAG.

I suspect you will need to keep the plates at the narrower part of the tube otherwise the voltage you need for deflection will be enormous...

I never tried the vidicons - I looked at winding my own coils which I suspect would be easy enough to get something working. I should think a fair bit of trial and error would be involved in getting it to work well though.

I keep meaning to get round to doing all this stuff but at the moment my workshop is piled high to the ceiling with half finished projects and stuff that had to be put away when we had the baby...also I own an old Land Rover which eats all my spare time just keeping it running.

Hopefully we'll buy a bigger place soon and I can have a real work-shop instead of the coal-hole that I use at the moment!

D
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Re: electrostatic deflection idea

Postby Harry Dalek » Thu May 28, 2015 12:32 pm

dominicbeesley wrote:Thanks Harry,

I used fairly small plates on the neck of the tube just after the gun assembly. I didn't try on the wider part of the neck as I had the deflection coils working as well as trying electrostatic, also the tubes were coated with conducting DAG.


Ok thats a good reason i was thinking you had it removed testing on the neck just before it angles so you tried just before the deflection yoke .

I suspect you will need to keep the plates at the narrower part of the tube otherwise the voltage you need for deflection will be enormous...


OK either it effects the focus or if you try and copy the yokes position voltages not overly safe now either of those are a good reason it wasn't used .

I never tried the vidicons - I looked at winding my own coils which I suspect would be easy enough to get something working. I should think a fair bit of trial and error would be involved in getting it to work well though.


Well it is pretty hard even with the corrrect yoke focus coil i noticed what that fella said in hes video it look him years to work out the deflection yoke was wired wrong and he was canceling out hes yokes deflection .

I keep meaning to get round to doing all this stuff but at the moment my workshop is piled high to the ceiling with half finished projects and stuff that had to be put away when we had the baby...also I own an old Land Rover which eats all my spare time just keeping it running.


OH yes the baby ! you are going to have to help the wife for a bit or there would be trouble having 3 kids you need to plan your spare time in advance a little bit at a time gets you there ...i am lucky my wife lets me do a little project work in the house but i keep it all small small scope small battery soldering iron so on you don't want to push your luck 8)

Hopefully we'll buy a bigger place soon and I can have a real work-shop instead of the coal-hole that I use at the moment!

D
[/quote]

Good luck a man need s big shed as well or space to build one :wink:
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: electrostatic deflection idea

Postby Harry Dalek » Fri Jun 22, 2018 10:30 pm

Been a while posting on this subject but finding a little more this may be of interest to others ,always on my to try list in the future .
Below a video showing a electrostatic charge does seem to work from the out side of CRT here directed more to the front but works ,i was keeping an eye on if it caused a focusing problem .


Some experimentation on a magnetic tube would be more helpful have to do it one day have a few laying around to try .
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The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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