Mac Plus Video signal convert to composite video signal

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Joined: Dec 20 2003
Posts: 7

Probably it is an old topics. 
I tried to follow "Macintosh Repair & Upgrade Secrets" to convert video signal. It describes how to make the TTL video adapter as Video Upgrades. The converted signal is to connect to PC-style TTL monitor.
Since currently the PC-style TTL monitors are not available, I need to convert again to any form of video signal. Or convert totally different way. Please help me how to approach this or if anybody has any answer, please let me know.

The TTL video adapter is to use one 74LS14 and one capacitor of 0.01 mfd for reference.

I wish to use LCD panel for the video and it allows composite or RGB video signal and it works well for Apple II series and replica 1.

Thanks

Shigeru

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Offline
Joined: Mar 12 2005
Posts: 117
Unless you have extensive kno

Unless you have extensive knowledge for making D/A circuity, it's going to be tough. The TTL is a digital signal. Composite or RGB is an analogue signal. There are two distinct problems. One is that the Compact Mac drives its video at a different frequency than VGA, NTSC or PAL video. So right off the bat you are dealing with a completely non-standard video format. The second of course is converting the digital signal to analogue in the first place. The Apple II, unlike the Mac, was always conceived to drive an NTSC television monitor, that never changed throughout its history despite the ability to add video cards into slots which the Mac Plus does not have.

Many have tried to do this, but I am not aware of anyone developing a solution. Since PDS & Nubus slots were developed before the VGA standard, no effort was actually made to adapt the signals for newer external monitors for which there were better alternatives like the LC.

There were a few third party companies that produced interfaces, but almost all of them required a customized monitor with a horizontal scan rate of 22KH, the same output of the Mac Plus. Television is 15Kh, which means you need a scan converter as well, after you've converted your signal to analogue.