CRT Schematic

[Guest steveskyhawk]

Does anybody know where to get a schematic of the CRT we all have in our 88-89 Reattas and Rivieras?

[padgett]

It is really two assemblies bolted together. The touch scream is in front and has the bag (ckt bd) on the side. The CRT assembly seems to have been made by Heath/Zenith of Benton Harbor MI. I understand it is basically an early PC video system.

[KDirk]

Padgett has this right, the CRT and attached circuitry were built for AC Delco by Zenith. The picture tube is a 5.5" green phosphor monochrome VGA monitor (320x200 pixel VGA mode 13 only AFAIK, 640x200 hi-res probably will not sync to this monitor) and the attached drive circuitry is pretty standard of the era. Of course, Zeniths were always a bit screwy in design vs. other big companies like RCA (at least for regular TV's) so this monitor may share in that reputation.

The touch screen is only marginally integrated into this setup, as it is a separate overlay panel (not fused to the glass like most touch screens) and the power and data lines for it are routed through the same harness. Because of this, the CRT can work essentially on its own with proper power and video input. Really just two separate parts/systems integrated into a common chassis.

If you really wanted to, you could drive it from a standard VGA port on any computer with a properly adapted cable spliced together. Not terribly useful, but it could be done by virtue of using what was (in the mid 1980's) a common PC video standard.

The video spec is the same as early vanilla VGA (such as the IBM PS/2 model 25/30 etc), but as implemented in the CRTC only mode 13 (320x200x16 color mode) is utilized. It is further "handicapped" by omission of the blue and red driver circuitry and interface lines to the monitor. Since GM only needed monochrome, that is strictly what Delco had put on the circuit board.

I've not looked at the CRT closely enough to see if red and blue input support were retained on that end. They are not broken out on the harness, so I doubt the circuitry is installed on the board. Even if it was there, all that would get you is 16 shades of green if the CRTC were programmed for color output and had the full RBG output implemented from the RAMDAC chip onward.

I am wondering if Zenith retained any service data on the CRT module, or if it was issued strictly through Delco. A google search on the chassis number on the CRT reveals very little, which isn't all that surprising.

KDirk

[harry yarnell]

Any adaptibility to the Olds Trofeo unit? That, I believe, was a COLOR (RGB) unit.

[KDirk]

Harry,

This has been discussed here by myself and others in the past. Technically, this could work by using the Reatta CRTC and Trofeo monitor (mounting considerations aside) but the Reatta CRTC would have to be modified to output color video. This would require two things:

1. The addition of some circuitry in the CRTC video output circuit to gain the use of the red and blue drive, which were omitted due to lack of need in the stock setup.

2. Modification of the CRTC firmware such that the pre-programmed displays would output in multiple colors. As it stands, the programming for the screen images is all in white, since that presents the highest intensity image on a monochrome monitor.

Mod #1 would not necessarily be all that difficult as long as a determination can be made on what components need to be added (and the needed additional wiring to the CRT as well).

Mod #2 is trickier, in that the program is stored on a chip (which can be "dumped" so that the contents can be read on a computer, with the right equipment, then programmed back into the chip once changed). I am of the belief that the program can be modified to do this based on information contained in an IBM patent for the system which outlines the hardware, development tools and programming language that was used to "build" the CRT system. Which is not to say it would be easy, but I think it is doable.

A Trofeo CRTC could not be used. I have one that I have dissected, and it is an entirely different unit. Think of the Trofeo version as a second generation design that was vastly improved in a number of ways. Since neither the basic hardware or the programming in the Trofeo CRT controller is identical to the Reatta version, it could not be used without much more extensive modification than I outlined in #2 above.

I would love to be the one to pull this off, but it is a very time consuming projcet that I cannot commit to under present circumstances, and I would need an 88 or 89 Reatta to use as a test bed for such a project.

A fully functional vehicle electronics system would be needed to experiment and debug any such changes, and it would be easier (and probably cheaper) to buy a car than to try and set it up on a test bench considering everything that would be needed.

So, that's where it stands.

KDirk

[Guest Richard D]

I think I will stay with my multi-color VFD 1990 for now, But a 256 color trofeo type display/ touch screen would be cool. Maybe 16 colors is enough.