Re: HV transformers

peter jones wrote:

> Just a quick thing for the technical people to think about!
>
> I was thinking the other day 'why do these transformers keep dying?'
> so i looked at the schematics.
>
> the atari monitors use a 20Khz drive and i think its a squarewave.
> (i have not checked with a scope)
>
> transformers of that period (1980) where designed to run at 15Khz,
> i doubt the factory that made them new they would be driven at 20Khz.
>
> also lopt's normally (in tv/monitors) do-not run with a squarewave,
> they run on short duration pulses with a trailing 'peak'.
>

Actually, they sort of DO run with a square wave, at least as far as the horizontal output transistor is concerned. The transistor is either full on or full off. And the
damper is either full on or full off. The combination of transistor and damper is on for the full visible scan and off only for retrace. Retrace is where the high voltage is
generated, and where the transformer is going to blow if it can't keep up.

>
> maybe the HV units would be more reliable if the frequency was reduced to 15Khz, and the voltage was increased to compensate for the reduced output voltage.???
> maybe the 555 oscillator should be modified to supply short spikes.???
>

The output voltage will depend on the current in the windings just before the drive transistor turns off and the combination of transformer inductance and resonating
capacitance. That combination determines the flyback peak voltage that generates not only the high voltage, but also all the other voltages. Reducing the frequency to 15 KHz
won't gain you anything, and can cause other problems if the rest of the circuit isn't changed to match.

>
> ALL I KNOW IS - TV'S AND RASTER-MONITORS DONT GO THRU TRANSFORMERS LIKE I GO THRU BEERS, AND THE ONLY DIFFERENCE BETWEEN VECTOR AND RASTER MONITORS IS THE TRANSFORMER DRIVE!
>

No, the only difference was the lack of quality control when the transformers were made. Has anyone had a Wintron transformer go bad?

The computer monitor right in front of you is running at 31.5 KHz (if in 640 x 480 VGA mode) or higher (if in SVGA). All the new HDTV sets are running at 31.5 KHz. If
anything, running the flyback at a higher frequency makes the supply more efficient. And that's a GOOD thing.

>
> LIKE I SAID - SOMETHING INTERESTING TO THINK ABOUT!!!
>
> ---
> Ïðèãëàøàåì ïîîáùàòüñÿ íà www.talk.ru
>
> ---------------------------------------------------------------------------
> ** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
> ** message body to vectorlist-request@synthcom.com. Please direct other
> ** questions, comments, or problems to neil@synthcom.com.

--
Windows:
32 bit graphical interface for a
16 bit patch for an
8 bit operating system written for a
4 bit processor by a
2 bit company that can't stand
1 bit of competition.
---------------------------------------------------------------------------
** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
** message body to vectorlist-request@synthcom.com. Please direct other
** questions, comments, or problems to neil@synthcom.com.