Re: IIgs Monitor Repair

[ferdimh@gmx.de]

On 10 Jan., 21:29, "Michael J. Mahon" <mjma...@aol.com> wrote:
> Jerry wrote:
> > I recently bought a Benq FP241W LCD monitor since my old Dell 19" CRT was
> > dying.  This new monitor has all sorts of inputs, including an NTSC RCA
> > jack, plus individual R, G, and B RCA inputs.  I haven't tried my IIgs on
> > it yet, but an Apple IIc works quite well.  There is a very slow roll to
> > the image, but it's quite usable even in 80-column mode.
>
> What, exactly, is a "very slow roll to the image."
>
> Does the image position change on the monitor?  Does a small "ripple"
> move through it?  I'd like to know more.
>
I think it is one of these:
1) The whole picture rolls very slowly as if it was out-of-sync.
2) The picture rolls 1/4 to 3/4 over the screen, then jumps to the
original position where it starts to roll again
3) The picture jumps up and down very rapidly.
I've seen all of these on different digital displays.
1 happens on my TV capture card with a bt878 chipset.
2 happened on a video projector.
3 is seen very often. Had it on a 100Hz Doublescan-TV, many video
projectors and TV capture cards.

All these are very often caused by the lack of interlacing in the
Apple ][s video output causing the decoder which actually counts the
lines not to sync properly.
This can sometimes be remedied by using a setting like "Old game" or
"Still display".
The only real fix would be to reprogram the video DSP...

Ferdinand