At 11:54 -0700 7/9/11, Chris M wrote: >--- On Sat, 7/9/11, Clark Martin <[email protected]> wrote: > >> > I recall seeing the mac video being designated a >> "composite" signal. >> >> Not even the Mac Plus is composite >> video. I've seen the connection to the >> analog board and there was, IIRC, video and both sync >> signals as separate lines. As a rule you don't use >> composite video for computers as it doesn't allow for a very >> crisp image. and the Plus has a crisp image. > > Generally this is correct. Composite-NTSC signals are "noisy" or whatever. > But I seem to recall many earlier color macs, if not most or all, pump sync > signals onto the green input. Now isn't that a composite signal? Maybe not as > convoluted as combining the entire video signal w/sync. And there may even be > some minor but mostly imperceptible degradation there too. It's just that are > different types of "composite" signals. If you've ever looked at a diagram of > an NTSC signal, w/the "back porch" and all other sorts of weirdness, you'd > likely get an indication of why assembling then disassembling the various > components results in something less then an ideal signal. > Honestly it's been years since I've even looked inside a compact mac. The > analog board combines a power supply and circuitry needed for the crt and > whatnot. At what point are you saying the syncs and video are separate (or > separated)? Every composite monitor separates the signals at some point. The > composite signal is "understood" to parts of the monitor, but it's useless to > the nitty gritty (crt, flyback transformer, etc) until broken down. >
I think the point is in the title of the thread. "CRT on a 9 inch Mac". We're talking about a Mac Plus or perhaps a Mac SE or SE/30 here. The Mac II and beyond had NuBus plug in cards to handle video. Everything, including video RAM, was on a plug-in card and there were lots of choices with synch on green and NTSC both in and out were available. Synch on green was nothing more than a blacker than black negative pulse added to the green drive during the flyback interval. Monitors were typically not "composite" . Apple's 15 pin "standard" had three color coax lines and separate horizontal and vertical synch. -- --> From the U S of A, the only socialist country that refuses to admit it. <-- -- ----- You received this message because you are a member of the Vintage Macs group. The list FAQ is at http://lowendmac.com/lists/vintagemacs.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] To leave this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/vintage-macs Support for older Macs: http://lowendmac.com/services/
