vertical windings design on 80's thru 2000's CRTs.

[Wizard256]

On current CRTs, the horizontal windings are open winding on the inside and fits along the curve of bell, but the vertical windings made me puzzled is that ferrite ring is split in half horizontally, held together with spring clips, the winding is wound around the ferrite ring at top and bottom. This wouldn't make enough magnetic field for vertical deflection because of complete ferrite "split ring" yet that did work even there is no gaps. How?

Cheers, Wizard

[old_tv_nut]

Can you post a picture? - not sure if I am picturing it correctly, but it might be opposing windings that produce a field across the neck.

[doogie812]

Originally Posted by Wizard256

On current CRTs, the horizontal windings are open winding on the inside and fits along the curve of bell, but the vertical windings made me puzzled is that ferrite ring is split in half horizontally, held together with spring clips, the winding is wound around the ferrite ring at top and bottom. This wouldn't make enough magnetic field for vertical deflection because of complete ferrite "split ring" yet that did work even there is no gaps. How?

Cheers, Wizard

Let’s look at magnets 101. A magnetic field will travel along the axis of the windings. Failure to have the ferrite core in place would give you another horizontal deflection magnet. Since the upper and lower coils are wound in series they buck each other forcing the field to be emitted along the windings. I hope this helps. Doogie

[Wizard256]

Ferrite yoke horn for vertical. Note interior view of those ferrite horn has no "poles".

http://www.google.ca/imgres?imgurl=h...w=1061&bih=846

other picture of what I'm talking about the ferrite horn with vertical winding installed.
http://www.o-digital.com/uploads/222...1992GL_430.jpg

As you can see internal view of the bare ferrite horn have no "poles" to project the magnetic field yet vertical deflection worked. That what make me puzzled for awhile.

Oh, I repair TVs for several years at TV shop. Too bad no more CRT stuff. I like the challege compared to flat panel board swapping and bad capacitors.

Cheers, Wizard

[old_tv_nut]

how's this?

[jeyurkon]

That makes it clear. Thanks.

[jeyurkon]

I decided to try a vizimag model to see how it would look. The coils are opposing.

John

[Wizard256]

You guys are AMAZING!! That made things so clear now. Thanks very much.

The need for the ferrite horn ring is to get center very intense due to two factors: to the horiziontal windings getting in the way due to high deflection angle CRTs and low voltage & low current of vertical IC?

Only two makers I had to replace or service yokes with alarming frequency were philips with bad vertical or horizontal (made top area to misconvergence due to bad yoke (what the cause?).

JVC CRTs with buzzing noise was drill holes and dig out foam pads (carefully!) in interior side plastic for varnish to get inside (required 3 dips that takes a week to do).

Only one CRT I had to replace for bad yoke due to RCA bonded CRT yoke. Shaking a fist at RCA for this foul manner meant CRT is at victim to possible bad yoke. (Fault was smelling of ozone while running).

Cheers, Wizard

[old_tv_nut]

The yoke design is very complicated because it has to do several things:
1) converge the beams at the edges of the picture when the center is correct (eliminates the need for convergence circuits)
2) correct pincushion distortion (or produce a form of pincushion that is easlily correctible)
2a) have modified arctangent distortion that can be corrected by a simple "S" shaped horizontal deflection current component
3) maintain low astigmatism and therefore good focus from center to edge
4) have an apparent center of deflection that can be simulated by a light tower for deposition of the phosphor stripes, thereby having good purity from center to edge
5) have inductance and resistance that is amenable to solid state drive

and probably more that I can't recall

[JCFitz]

The reason the Philips yokes did that was the pole pieces under the vertical windings would come unglued. The Philips yokes also buzzed when this happened.

Originally Posted by Wizard256

You guys are AMAZING!! That made things so clear now. Thanks very much.

The need for the ferrite horn ring is to get center very intense due to two factors: to the horiziontal windings getting in the way due to high deflection angle CRTs and low voltage & low current of vertical IC?

Only two makers I had to replace or service yokes with alarming frequency were philips with bad vertical or horizontal (made top area to misconvergence due to bad yoke (what the cause?).

JVC CRTs with buzzing noise was drill holes and dig out foam pads (carefully!) in interior side plastic for varnish to get inside (required 3 dips that takes a week to do).

Only one CRT I had to replace for bad yoke due to RCA bonded CRT yoke. Shaking a fist at RCA for this foul manner meant CRT is at victim to possible bad yoke. (Fault was smelling of ozone while running).

Cheers, Wizard

[Wizard256]

The Philips yokes didn't buzz. Just misconvergence at top. Very noticeable with channel numbers displayed at upper right on the hotel sets. (usually 25" and usually 2001 thru 2005 chassis)

Cheers, Wizard

[JCFitz]

Originally Posted by Wizard256

The Philips yokes didn't buzz. Just misconvergence at top. Very noticeable with channel numbers displayed at upper right on the hotel sets. (usually 25" and usually 2001 thru 2005 chassis)

Cheers, Wizard

The 90s ones would make a sorta rattling or maybe buzzing noise. And the later ones do use a similar design yoke.So I bet the pole pieces have moved out of position or demagnetized causing the misconvergence. I have heard although not as pronounced a rattlling noise on the worst case later ones and the convergence was really bad on those.