Is Lindsay?s ?SM? a fraud?

[BEP]

Any electron beam created spreads rapidly, causal that the electrons composing the beam share the same charge. In essence, they repel each other. This sucks if you need a good tight beam hitiing just a few phosphorescent dots on the screen, instead of thousands of dots at once. The yoke provides a magnetic field with a small aperture (hole in the field) in the middle, which keeps the electrons from spreading. This accounts for the cores and their coils.

However, the beam needs to be focusable at more than one spot on the screen. Therefore, they provided deflection coils to manipulate the position of the aperture. IE the funky shaped coils is the center of the yoke deflect the hole in the field, moving the electron beam.

Paul,

When you have some time could you please direct me to an information source that agrees with the above statement?

Thanks,

John

[pauldude000]

@BEP

Which statement? (I made many in what you quoted.)

Are you questioning that electrons all have the same polarity of charge? (any textbook)

Or are you questioning where like charges repel, and opposite charges attract? (also any textbook. Look up "electrostatics" for some basic info.)

@Loner

The gun does produce the initial beam. However, the beam will want to "spread" because all of the electrons composing the beam carry the same charge.

You posted that with the removal of the deflector coils from the circuit, you get a "dot" in the center of the screen. A quick question for you. Was this dot 1 phosphorescent pixel wide and tall, or was it hundreds of pixels. Think of the size of the beam produced by the gun, and remember that it has to energize one pixel within a set of three (R,G,B) at a time, pixel set by pixel set, line by line to produce a rasterized color picture.

Man, you mentioned your SAMS, that brought to remembrance a small stack of the things I used to have laying around. Come to think of it, somewhere I should still have my old "Handbook of Electronic Circuits" book. Big "ye old ten pound bookshelf filler". I ought to dig it up, and see what it has for some new(to me)/old(for today) oscillator ideas.

Paul Andrulis 

[BEP]

@All

I thought I had a solid ground in CRT operation. At least scopes, B&W and also the Trinitron method. I must have some understanding as I've performed repairs and builds on all three.

My understanding:
The idea of a moving/resizing aperture didn't match what I understood. It (if it is an aperture) doesn't move. The strength of the field varies which causes a variation in deflection of the beam.

The beam spreads? I know this is in some text books as 'like charges repel' but the application of that term is incorrect as these are 'moving charges'. Not only moving but moving in the same direction at the same speed therefore they attract and the beam does not spread wildly.

The latter is where the laws of magnetics are hopelessly screwed as the theories of Gassman(sp?) were used instead of Ampere's correct experimental results by the folks that mistranslated the treatise on magnetics.

This is one I battle frequently and found true during short-circuit tests almost 30 years ago.

Like charges travelling parallel attract
Like charges travelling anti-parallel or not moving repel

Unlike charges travelling parallel repel
Unlike charges travelling anti-parallel or not moving attract

It is in some books this way just not many.

I expect arguments on this but I won't as the reality of jumping buss bars and cables during a short circuit can't be denied. Neither can that single dot on the screen when the beam is emitted from a fairly broad cathode element yet winds up as a tiny dot on the screen - even when the magnets, charged plates and coils have been turned off.

I don't mean to insult or start a heated discussion. The description of CRT operation just seemed very wrong to me.

[wattsup]

@otto

Sorry to bud in guys but I have a question for otto.

I found three more yokes today. Now I have at least two big ones. What do you do with the yokes. Do you have to cut all the wires and remove the glue to then remove and only use the ferrite yoke core, or, are you winding your coils over the complete yoke as is.

What a pity to dissect such a fine piece of coiling. I think I will keep two intact and play with the original coils a bit also.

[otto]

Hello,

I have removed all the original coils and the glue.. Im using only the iron powder cores. The most time Im using only a quarter or half of the yoke because then I can quickly remove the controls and wind new ones.

I pulsed also the complete yokes. A fine light but there was no collector and so I made one with lamp wire. Just a few turns. I have 1 yoke that is complete with the coils - intact and working. Hmmm....I said already that this yokes looks like a TPU but without  the collectors.

I think that I can learn a lot with this strange coils. Its easy to work with this cores. Only a few turns for the collector and for the control coil and thats it! In a short time you can easily change your controls or collectors.

Please, when you play with such a TPU be careful because there is a really big current. Dont pulse the coils without a load and maybe it would be clever NOT to connect your scope on this f...g TPU. The scope probe can be near the TPU and you will see the same signals at lower voltage settings.

Otto