Is it possible to connect a 9" CRT to a VGA motherboard ?

[Bunbury]

Hi

Everything is in the title.

The mod I'd like to make is to put a small motherboard inside a Mac Classic case.

As this will be a server, I'd like to keep the 9" CRT as the monitor and therefore connect it to my motherboard.

Is it possible ? How ?

Thanks

 

[BadGoldEagle]

I think you'll like this: https://nerdhut.de/2016/06/26/macintosh-classic-crt-1/

 

[Trash80toHP_Mini]

Nice hack, but waaaaaaaaaaaay over my head.

Why couldn't he just add RTC function to the Pi and why the heck isn't a Real Time Clock built into the Pi? :

Doesn't look like grayscale, one wonders about that possibility?

Reason for questions:

Offhand, I can't thing of anything more cool than his CPU and boards mounted in a drawer that pulls out the breakout slot of an SE or SE/30. Would height/width preclude packaging his components within that opening's profile? Looks like my OrangePi would fit with minimal filing of the recessed lip for Ethernet/USB/IDE connector clearance

edit: very cool idea for your server enclosure! [] ]'>

 

[Gorgonops]

Why couldn't he just add RTC function to the Pi and why the heck isn't a Real Time Clock built into the Pi? :

This guy made it work on a Pi. Reading between the lines I think the guy doing the Beaglebone writeup missed the fact that the Pi does have some hardware acceleration built into it that makes this possible (if slightly awkwardly) and instead concentrated solely on doing the bitbanging *entirely* in software. He made it work on the Beaglebone by using the PRU, which is a fully programmable co-processor, not just a "real time clock".

Strictly speaking the best way to drive a Mac CRT from a Raspberry Pi would be to leverage its built-in "DPI" (Display Parallel Interface) support. This is mentioned in passing in the article I linked above (he misspells it "DPM".) The advantage would be that by using it you don't have to make make software understand you're using some weird "fake" framebuffer that's being bitbanged out via ad-hoc methods, you'd have something that looked like an "official" according-to-Hoyle framebuffer that at least in principle works with X11, etc, directly. Here's an article about how it works in general, what math you need to do, etc. That article is about making it work with TTL LCDs, but it's pretty flexible. Here is a VGA adapter that can use it, and all it uses for parts is some resistors. Here's the document on the Raspberry Pi website that discusses the software configuration for setting up hsync and vsync

timings for non-standard resolutions, which of course you'd need.

My first crack at Googling up someone actually following through with this idea to drive an old Mac monitor hasn't panned out, but I'd kind of be surprised if nobody's done it or something like yet.

Doesn't look like grayscale, one wonders about that possibility?

Not without modifications to the analog board hardware. (The internal grayscale cards for SE/30s accomplished this by replacing the board that goes on the CRT neck.)

Of course, these ideas for driving it with a Raspberry Pi don't really help if the goal is to use it with a PC server motherboard. Honestly your options there just aren't very promising. There was a project (links to it are somewhere on the forum) for using a small ARM board to convert the CRT into essentially a USB-driving framebuffer you can drive from a Linux computer, but it was pretty involved and could only manage single-digit FPS screen refresh. (Which might be fine for a server.) Your best bet really would be to chuck the original guts and mount a 9" monochrome VGA monitor in its place.

 

[Bunbury]

Thank you all for your help.

Replacing the CRT with 9" VGA is also OK.

But where do I find those?

Do they even exist?

 

[Gorgonops]

9" Monochrome VGA monitors were pretty common for a while in the 1990's; they were sold for use in things like cash registers/Point-Of-Sale (POS) systems. Here's an example for sale on eBay. Beware that these usually only support the barest minimal VGA modes (640x480 graphics and standard 720x400 text); if you're *really* lucky they'll to 800x600@56hz and 1024x768 interlaced, but both of those are real retina-burners. If you just want a text console it'll do the job, but for a GUI they're... not great. (Still higher resolution than the 512x342 of the original monitor, granted.)

 

[Trash80toHP_Mini]

.  .  .   these usually only support the barest minimal VGA modes (640x480 graphics and standard 720x400 text); if you're *really* lucky they'll to 800x600@56hz and 1024x768 interlaced, but both of those are real retina-burners.

Why are they retina burners. 56Hz isn't far off 60Hz? 640x480 looks sweet on this one:

https://www.ebay.com/p/IBM-4707-9-Monitor/52113641?iid=253205189796

 

[Gorgonops]

To my eyes 56hz is just too slow for white phosphor, it looks like a strobe light in my peripheral vision. (60hz actually isn't fantastic either, I always used to like the longer green and amber phosphors better. Of course, VGA monitors in anything but white are rare as hen's teeth.)

In any case, flicker doesn't show in photos.

 

[Trash80toHP_Mini]

I found a curious 9" CRT in one of my Compacts. Is this a Macintosh CRT connector? I'm thinking the Connector/CRT for my Compaq Portable II got mixed in with the Compact CRTs?

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Still searching, haven't found specs on the Portable II video yet, but it doesn't look promising the Portable and Portable III outputs were CGA 320x200x16 color (shades of gray) or 640x200x2 color. RGB out. FWIW, the CRT and controller board would fit very nicely into a Compact Mac.

Meanwhile: John Cleese on the Compaq Portable II  :lol:                 

 

[EkriirkE]

Here's another project repurposing the CRT/case http://spritesmods.com/?art=macsearm&page=1