Re: 50 / 60 Hz in Display control panel

[spec@vax2.concordia.ca (Mitchell Spector)]

In article "Ken Schunk" <kschunk@nycap.rr.com> writes...

>I recently purchased an Apple IIgs, and I'm having one problem with it. I
>can't get it to display composite video correctly on most of the TV's that
>I have tried. Only an older B&W with a vertical hold control allows me to
>get a stable picture.

    A plain RCA cable running between the back of the IIgs and your
TV (with 'Video IN' terminal) or VCR should work fine. It outputs a
composite video signal through the composite port (just below the
power plug) which is decent enough when it is emulating an older
Apple IIe, but in native mode your going to want an analog RGB
monitor for the GS's color and resolution. In either case, you
will get a stable viewable picture, just not necessarily the
nicest.

>I noticed in the Display control panel that it indicates "50 Hertz".
>I also noticed that my emulator software says 60 Hertz. Just what is
>this 50/60 Hertz item, and would it have any impact on the composite
>video output?

    That is the problem. North American (and Japanese) TV sets
operate at 60 Hz and the IIgs is sending a video signal at 50 Hz.
The vertical scanning frequencies don't match, which is what is
responsible for determining the refresh rate of your screen. TV's
and composite monitors seem to operate on a fixed frequency, so
sending them something they're not expecting is going to give an
unstable image, to say the least.

    To fix this, turn on your IIgs while holding down the 'Option'
key (or if already on, press and hold down Option-Control-Reset,
while continuing to hold down the Option key after releasing
the others). When the menu appears, select option "2" by pressing
the 2 key. This is set the refresh rate back to 60 Hz, as well
as restore all the factory Control Panel settings. You may want
put them back, which can be done by repeating the above steps
and pressing "1"m or pressing and holding down Apple-Control-Esc
and then selecting 'Control Panel'.

Mitchell Spector
spec@vax2.concordia.ca