Re: Wintron transformers

Zonn wrote:

> On Thu, 12 Jul 2001 18:47:02 -0500, Joe Bachmann <joe.bachmann@newmail.net>
> wrote:
>
> >Thank you for the info... With that in mind, I found a site that looks like it may sell just the thing we're after:
> >
> >http://www.emcohighvoltage.com/emcoindex.htm
> >
> >Link to section I am referring to: http://www.emcohighvoltage.com/crt.PDF
> >
> >I am looking at the CRT-200 or 6000 series.. This may be easier than designing something, however I don't know the cost..
> >
> >JB
>
> Those are cool! If they are cheap enough, forget Wintron.
>
> Designing a supply using an off the shelf flyback is not easy.
>
> This is my take at doing so. This is more Rodger Boot's field, but here goes...
>
> Everyone seems to forget the flyback circuitry needs a yoke (or the equivalent
> inductor -- this is a tuned circuit and must remain so to work properly) in
> order to produce the HV needed.

Not necessarily, changing the resonating capacitors to match up with the inductance of the flyback alone gives you the same
effect.

> The second thing shrugged off seems to be HV
> regulation -- needed to keep the picture from growing and shrinking as the
> vector count on the screen goes up and down.

This can be done by sensing one of the other outputs.

> The schematics I've looked at all run the flyback's primary on rectified 120vac.
> This requires that a isolation transformer be used (to avoid electrocution -- a
> bad thing). HV regulation on the raster CRTs I've looked at is done in a
> specialty chip that also controls the horizontal (and sometimes vertical) sync.
> It supplies the free running oscillator that is locked onto the HV sync pulse
> when detected. Way over kill for what we need. But if we design the oscillator
> ourselves, we need to design the regulation circuitry also.

For the most part monitors and TV sets don't have much for regulation, they just depend on the INPUT (from the low voltage
supply) to be regulated. A vector monitor actually doesn't need to supply as much current as a raster monitor, so it SHOULD
be simpler.

> You will also need the current transformer that is used to drive the horizontal
> deflection transistor.

Maybe, maybe not. Perhaps a power FET could be used. This would allow direct drive and (if it is a HEXFET) the internal body
diode could be the damper.

> All and all, to use a flyback, you need to design a large part of a horizontal
> sweep circuit that needs to be run with a isolation transformer. It gets
> cumbersome and expensive -- even with a $17 flyback.

A 555, a power FET, a flyback (preferably the exact part used in a K7000 raster monitor), and some simple regulation. And a
few "glue" parts such as the resonating capacitors. The flyback has the HV rectifiers, anode lead, and focus/G2 pot assembly
built in.

Back in my college days I powered a black and white CRT using a auto ignition transformer as the flyback. The design was
wrong in so many ways, but worked anyway. I need to get off my dead ass and try designing a supply. At the last local
hamfest I bought a 6BK4 tube to use as a high voltage load. Using that as a dynamic load it should be possible to FINALLY
design a supply with kick-ass regulation.

> Things get much simpler when you start with a properly wound HV transformer (not
> a flyback). Just look at how simple the HV sections of X/Y monitor are compared
> with raster monitors. Raster monitors use flyback simply because the Horizontal
> section is already there, and is real easy to tap into to get the HV needed.
> That and flybacks are a very efficient way off generating HV.
>
> The opposite is not true, it's a pain to start with a flyback and build the
> horizontal circuitry to support it.
>
> These are the reasons that seemed to have stopped every attempt at building an
> HV replacement since I been reading vectorlist. Not the threat of lawsuits.
>
> On the other hand it looks like "low cost" 350 series would run all the B&W
> vectors, and the CRT 200 would probably run the colors -- even the filament in
> an amplifone! Very cool!
>
> -Zonn
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Received on Fri Jul 13 06:52:02 2001