Re: AppleColor Composite Monitor and IIGS

[Stephen Shaw <xstephenx@apple2.org.za>]

On 28 Nov 2001 16:50:59 GMT, Michael J. Mahon wrote:

> Matthew Styles wrote:
>
>>I opened it up today, and found some different knobs, including focus. There
>>was a group of these on the main (analogue?) board. Can one of these be
>>adjusted or is there a service source article or similar that will tell me
>>what to do?
>
> and earlier:
>
>>>> Also, the screen seems to disappear below the bottom, like
>>>> the vertical position needs to be adjusted, is there a way to change this
>>>> (possible an internal vertical adjustment knob)?
>
> The vertical (and horizontal) positioning on most monitors is not a
> potentiometer control, but a pair of circular magnets near the front
> of the deflection yoke, with tabs protruding.  These tabs are used
> to rotate the two ring magnets to adjust the magnitude (cancelling
> or reinforcing) and direction (azimuthal position) of the resultant
> positioning magnetic field.
>
> They are often fixed with a dab of paint, but can be carefully freed
> and rotated to produce the correct alignment.
>
> FWIW, the adjustment seldom needs to be changed, so you might
> first check the vertical size and linearity controls to make sure that
> they aren't the problem, rather than centering.


Could be dirty potentiometers (i.e. knobs) clean with Cramoline or bad
electrolytic caps. I haven't worked on a Color Composite but from the sounds of
it I'd change all the caps connected to the pins of the horizontal output chip
(possibly
a TDA1170).
Good luck.


-- 
Why make things easy when you can make them complicated!