Re: OT: Classic Macs group?

["Paul G." <carbide@egine.com>]

On Jun 10, 3:01 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:
> Paul G. wrote:
> > On Jun 9, 9:35 pm, "Michael J. Mahon" <mjma...@aol.com> 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's been so long, I can't remember what else I did to adjust the
> > display on these compact Macs. We're talking 12 to 15 years ago. I
> > seem to recall expanding the horizontal and vertical to fill the
> > screen- often that tiny screen had 1/4" or more of unused screen at
> > all four edges. Adjusting those magnets put the finishing touches on
> > the job.
>
> The centering magnets will shift the raster, but not change its size.
>
> Width and height should be adjusted by the correspondingly named
> controls, if they are present, or can they be affected by the linearity
> controls, though the linearity may suffer.  ;-)  On some monitors, even
> the vertical hold control has an effect on raster height--such are the
> imperfections of sweep circuits...
>

OK, I got off my butt and took another look at the analog bd in my
junk box. I then typed "mac plus" r55 r56 into Google and bingo, here
are the schematics and exactly the info needed to adjust and
troubleshoot:
http://home.earthlink.net/~gamba2/images/plus_analog.PDF

Looks like a leaky C1 would be the likely culprit for a horizontal
offset, detailed info on diagnosis and replacement is provided.
-Paul