Re: Macintosh 12" monitor on a GS?

[supertimer@aol.com (Supertimer)]

Zorin <jflynn02@cs.uif.edu> wrote:

>I picked up a Macintosh 12" RGB monitor at a swapshop for $5, and was
>dissapointed to find that even though it has the same plug, it doesn't
>sync to the GS's 15KHz horizontal rate.
>
>Is there any way of hacking this monitor into syncing at 15Khz, rather
>than the faster rate? The image is steady, but looks torn up. Vertical
>scan rate appears to be the same, but horizontal is twice as much as it
>should be (30Khz). The torn picture is very crisp, you can make out the
>colors that should be on the screen, but nothing more.
>
>It was only $5, so it's not a big deal, but it would be nice to hack the
>thing into working. }:)

Yes, you can hack it to work.  Pretty straight forward conversion if
you know what you are doing or you know a monitor technician.

Here's what Jim Poore, who used to post to comp.sys.apple2 says:

James Poore <aw133@lafn.org> wrote:

Technically yes it is possible if you want to go thru all the trouble.
The Horiz freq is the easy part that involves changing a resistor value.
Then you have to change the hipass network in the sync section....wait 
we're not done yet...the timing capacitor for the sweep time has to be 
reduced otherwise you will have a 50% overscan (actually yoke timing not 
sweep timing) once thats done, then you hope that the centering of the 
horizontal sweep is still centered and finally pray that the flyback 
doesnt fry due to excessivensweep times and that the X-ray protection 
circuit doesnt trip prematurely.  Now we havent discussed voltage 
reduction in the supplies that get their power from the flyback nor the 
reduction of effectiveness of the supply filters.

I *Have* done a monitor that was originally set up for 30KHz horiz rate 
and set it down to 15.750KHz with 6 part-changes (4 resistors-2 
capacitors) and it worked.