Re: Apple II video problem?

[Polymorph <polymorph69@hotmail.com>]

On Aug 3, 11:16 am, "Michael J. Mahon" <mjma...@aol.com> wrote:
> Polymorph wrote:
> > On Aug 3, 5:49 am, "Michael J. Mahon" <mjma...@aol.com> wrote:
>
> >>MdntTrain wrote:
>
> >>>On Aug 1, 6:34 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:
>
> >>>>Not laughing, but wondering whether the horizontal hold control
> >>>>(inside the case) could have made the two cases much more similar...
>
> >>>I can still try that.  Right now, I have HHold adjusted perfectly
> >>>centered between the two points of going crazy (losing sync?).  Moving
> >>>it one way does cause, at one point, the left shift video to suddenly
> >>>shift more towards the center.. but it was near enough to the "going
> >>>crazy" spot that I didn't feel secure leaving it there and opted for
> >>>the middle.   I did not try plugging in the Rev 7 board at that spot
> >>>to see what happened either.
>
> >>>What are you thinking?
>
> >>I'm thinking you have it correctly adjusted at the midpoint.  ;-)
>
> >>Some monitors have horizontal phase lock loops that respond to
> >>the average (middle) timing of the horizontal sync pulse, while
> >>others (digital?) will respond more to the leading edge.  This
> >>could make the difference in horizontal phase, since the leading-
> >>edge-to-start-of-window timing is apparently nearly constant across
> >>models.
>
> >>-michael
>
> > I have a different, but similar (I think) problem with one of my IIgs
> > monitors. It displays a reasonable image, however the whole thing is
> > on a slight lean. That is, one top corner of the display is slightly
> > higher than the other (can't remember which right now - I'm at work).
>
> > I tried messing with the centering rings inside the case, but gave up
> > as I couldn't seem to remedy the problem. By turning the centering
> > rings, I could change the "tiltedness" somewhat, but at the cost of
> > image quality (colours became separated and image deteriorated
> > greatly). So I gave up and returned the image to its original state
> > (or as close as I could get it). I may have actually made it worse
> > rather than better, as I am sure the image was a bit sharper before I
> > twiddled with it (maybe its just me be negative though).
>
> > Although I resigned myself to the fact that the image would remain on
> > a slant (and I have kinda got used to it), can anyone suggest
> > something else that I could try to realign the image? Could it be the
> > result of some component(s) approaching their used-by dates? Maybe
> > some ageing capacitors or something?
>
> The solution is to rotate the yoke on the neck of the CRT.
>
> It is common for the plastic liner of the yoke to have some stiction
> with the glass of the CRT neck, and there is a "hose clamp" around
> an extension of the yoke whose purpose is to keep it from moving
> relative to the CRT, but carefully loosening the clamp will allow
> the yoke to be turned (or moved backward, which you don't want to
> do) to align the raster to the CRT bezel.
>
> It's really pretty easy, but be careful not to apply too much or
> too sudden pressure to the glass neck.  It's strong, but not
> unbreakable.  ;-)
>
> You will find a mirror helpful, as well as a program to display,
> say, a white HGR screen to make alignment easier to see.
>
> Generally, centering will be unaffected, but if it needs adjusting,
> this would be a perfect time to trim it up.
>
> -michael
>
> NadaNet file server for Apple II computers!
> Home page:  http://members.aol.com/MJMahon/
>
> "The wastebasket is our most important design
> tool--and it's seriously underused."- Hide quoted text -
>
> - Show quoted text -

Thanks Michael, I figured you or one of the other hardware guru's
would know how to fix this.

Next time I feel brave enough to crack open the monitor case, I'm
going to give this a try.

Although I read posts from you and others about it being relatively
safe to work on a monitor due to low current, I still get a little
uneasy every time I see that "WARNING 10,000 VOLTS" sticker.  ;-)  I'm
in Australia too, and have 240V as opposed to your 110V which makes me
even more nervous. But I did it once before, so I'll give it another
go.

Thanks again,
-p