Video Out on the Lisa 1 and 2/5

[CelGen]

I've always been curious about the RCA jack on the Lisa 1 and 2/5 that was marked VIDEO OUT. Until today I could only determine:

-The signal is composite

-The signal is NOT NTSC/PAL standard.

Then today I finally found the more detailed specifications to the video on the Lisa which shed a light on it.

-The output resolution is 364x720 (720?? Holy crap!)

-The Horizontal refresh rate is 22.9khz

-The "Dot Rate" is 20mhz (this does NOT seem to be the Dot Pitch I know[/url)

-The main refresh rate is 60hz (AC line)

 

Well no wonder I could never get it to sync properly on anything. That resolution and refresh rate are absurd. I cannot think of anything that would sync to that but it's a big world so I'm curious if we can put our minds together and finally see if we can make something properly use that video connection.

 

[NJRoadfan]

A monitor like the NEC Multisync and Multisync II can support this since they support horizontal sync rates that low. I think that resolution should read as 720x364 though (some sites reverse the numbers for some reason). The horizontal scan rate matches up.

Wire to composite signal to the R, G, and B pins (since its monochrome). A sync on green monitor should "just work", if you need composite sync on a separate pin, use a LM1881 circuit to strip the video and feed the sync output to the appropriate pin on the monitor.

Hmm, that horizontal scan rate is VERY close to EGA rates. Assuming the signal is analog levels and not TTL, something like the GBS-8220 can upscale it with just a cable.

 

[CelGen]

Hmm. I never actually attempted a typical muitisync monitor as I wasn't expecting it to be that simple to wire it for such. I'll look around. I think I got a multisync monitor in easy reach to test with.

 

[NJRoadfan]

Page 24 of this document may apply as well, its possible that the video output will appear inverted (black pixels appear white) on your monitor: http://www.ccadams.org/se/classicmac2.pdf

Looks like classic macs have a similar horizontal scan rate too.

 

[lisa2]

I don't understand why the name of this tread is "Video Out on the Lisa 1 and 2/5",  All Lisa (AKA MacXL) models have a RCA video out connector, not just the 1 and 2/5.

 It's just a mirror of the internal video signal, my guess is that apple intended this to used for attaching large displays/projectors for presentations.  Today, everyone is used seeing to a powerpoint presentation on a large display, but in 1983 this was a very high tech compared to using slides or transparencies. Slides and transparencies were very time consuming and expensive to produce, and so was easy to justify purchasing an expensive mutlit-sync display for doing this if you did many presentations.  Highlighting Lisa graphics capabilities, this could have been the Lisa's killer app from apples perspective in the early 80's, so it makes sense to me at least they put the jack in the design. 

Rick

 

[CelGen]

Brain fart. I was thinking about the parallel port on the Lisa 2/10 and XL which was omitted on the revised cardcage.

The reason it's confused me for so long is that almost all the Lisa informational videos out there always seemingly have the camera focused on the screen and never just recording directly from video output. In fact I have never seen it used once.

 

[NJRoadfan]

Video with those scan rates weren't easily converted to NTSC with early 80s technology.

 

[mactjaap]

Is there anyone who actually connected a working monitor to a Lisa?