Re: Cinematronic HV question

On Thu, 03 Aug 2000 21:23:38 -0700, you wrote:

>> 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.

        Ahhh, that would explain why the Keltron-type schematic shows a set of
empty test points where the 1.2K resistor used to be... some yokes
required it and some didn't. (Apparantly, they did change CRT vendors at
one point, because the Keltron-type schematic does talk about needing an
extra resistor in the power-supply section for an "Amperex CRT".)

>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?)

        Actually, the +/-18V regulators are not used at all in the Keltron-type
design; the Keltron HV supply takes +25V and +90V.

        Really, the only thing that keeps me from thinking that it's an easy
sway is that there _is_ a significant amount of circuitry added to the
power-supply sections between the Rev.A and Rev.B versions of the monitors
with the old-style HV section. The Rev.B additions were carried through to
the Keltron-type design (a.k.a. "Rev.G", according to the draftsman's block
in the corner), so if you have a Rev.A monitor it _might_ be a little more
complicated than just figuring out where the wires go. :/
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Received on Thu Aug 3 08:56:55 2000