Re: Cinematronic HV question

On Wed, 02 Aug 2000 20:43:22 -0500, solarfox@texas.net wrote:

> The DAC and deflection-driver circuits look the same across all three
>designs, except that the "Keltron-style" schematic shows an empty space
>where R122 and R222 used to be... These resistors were paralleled across a
>.1uF capacitor and a 360 ohm, 1W resistor in series, and the whole trio was
>paralleled across the deflection coil, like so:
>
>(warning: ASCII art ahead!)
>
>--------------------------o---------------------
> ! !
>(replace the _'s with ! !
> "1" for the vertical ---o--- !
> deflection circuit ! ! !
> and "2" for the ! ! C_02 !
> horizontal) ! --- 0.1uF !
> ! --- 100V ----
> R_22 \ ! _)
> 1.2K / ! _)
> 1/2W \ \ R_23 _)
> (?) / / 360 ohm )
> ! \ 1W ----
> ! / !DEFLECTION
> ! ! ! COIL
> ! ! !
> ---o--- !
> ! !
> ! !
>--------------------------o---------------------
>
> I can't imagine this has anything to do with the Keltron supply...
>does anyone know what removing the 1.2K resistor from this circuit _does_
>do?
>
Those were apparently there to compensate for non-linearity in the yoke.

I switched yokes between monitors at one time and for the life of me could not
get the little lines to match up on the edges of the monitor. Removing the 1.2k
resistor fixed things right up.

apparently the board change coincided with a yoke change. If you've changed
yokes and cannot get the line edges to match up, this would be the place to
look.

> In any case - at _first_ glance, it doesn't look like the Keltron will
>work as a drop-in replacement for the old-style HV section... but, now
>that I have all three schematic sets in one place, I'm going to go through
>them with a highlighter pen and see _exactly_ what the differences are; it
>might actually be do-able with only a bit of tweaking. I'll keep y'all
>posted. :)

I also have an old Space War monitor with a dead HV power supply. I also
figured it would not be that hard to use a newer HV supply -- though I have yet
to do it. If I remember correctly they added a spot on the board to plug in the
HV supply, but still left all the traces for the older supplies. I don't think
it will take much more effort than figuring out where the wires go, and possibly
removing some key components from the old HV supply (like the 18v regulators?)

The newer supplies are nicer anyways since they regulate much better which leads
to less blooming effects.

-Zonn
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Received on Thu Aug 3 00:26:01 2000