Re: OT: Classic Macs group?

["jsnospam@cimmeri.com" <js@cimmeri.com>]

Michael wrote:
> Although Paul's suggestion to use the centering magnets would certainly
> move the raster, the fact that it's fine with another analog board
> indicates that it's actually the sweep timing that's off, not the
> raster centering.
>
> The control you're looking for is the "horizontal hold" or "horizontal
> lock" or "horizontal frequency" control.  It is often an adjustable
> slug in the horizontal oscillator coil (not the horizontal output
> transformer).

Michael,
I agree that the sweep timing is off.

The circuit appears simple.  One of the outputs of the flyback
transformer is paralleled to gnd via a rectifier, and parallel to gnd
via a  .033uf cap; then it goes in series to a {coil + resistor
paralleled to each other}; then through the "width" adjustable coil;
then to a unipolar electrolytic cap; then straight to yolk.

The only coil adjustable here is the width one.   I do know that the
previous {coil + resistor} combo have some effect on "horizontal
linearity" whatever that is.. but they are not adjustable.

It's possible that the sweep circuitry prior to the flyback is off
somewhere, but I suspect more likely *after* the flyback.   I checked
the value of that final unipolar cap -- and the capacity is good...
but if the ESR of it were too high, could that influence the timing?

~ J