OK. Not wanting to pay $500.00 for a younk style sony 10 inch trinitron that is already VGA 60Hz... I want to convert my CC Ab to 60Hz VGA mode and build the VGA to RGB circuit that is posted in the old forum. The link is here (http://www.hut.fi/Misc/Electronics/circuits/vga2rgbs.html).... I need to know this. Can I do this and include the 5V from a small power supply and tweek this into usable stuff? I got the feeling from the old thread in the old forum that I could. The guy said that his image was over bright. I am remember some brightness tweaks that are near the flyback and cl26 position that are not on the edge of the AB where all the other tweaks are. Am I nuts to try this?? Also, I have read and re read the FAQs... I need to ultimately mate this to a db15 standard VGA plug to get this to mate to a PC video card. Anyone with more info on this please reply. I really want to get this project off the ground and install my shuttle Pentium 4 2.5 Ghz with Radeon 9600 pro. Thanks in advance. :mac:
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It should be do-able, though I've never done it! My guess is that a major factor with the brightness issue was impedence matching on the video lines going in to the a/b. Put a 75 ohm resistor between of each the main lines and ground, and I'd expect much better behaved signals.
Essentially you mean 75 ohms between red green and blue? How did you come to that conclusion?
Some links from the old forum that you might find helpful:
Relating to sync.
And brightness. I haven't actually tested this yet, but probably will next week. I have the brightness/control PCB from a donor Mac monitor, I'm going to see if that will work.
No - I think I mean 75 ohms between R and ground, B and ground, and G and ground. Based on what normally happens when video signals are propogated, and hazy memory of impedence matching lectures!
May not work, but worth a whirl.
Thank you... on a side note: I have a small dark burn type spot on my analog board around DL21 and DL22.... it worked when I pulled it and have not applied power at all while modding. Should I swap these components for new ones?? The board did work before I modded it and I have not done anything since.
Scott-- not to beat a dead horse here, but if you remove the CC's yoke and AB and replace them with the yoke and AB from a Macintosh Color Display (MCD), you're 99% of the way there.
Such a mod gives you a 10" Trinitron tube with a mac-style DB15 connector. The wiring attached to the MCD AB also still includes the built-in contrast and brightness controls.
All you need is a Mac-VGA monitor adapter, and of course those are very cheap and easy to come by.
Finally, if you're planning on installing your Pentium mobo inside the CC case (as I presume you are), the MCD's AB is smaller than the CC's, so that should help in terms of space considerations too.
So any 12" to 14" Apple Trinitron external monitor's yoke and analogue board should work with the CC? That's the best idea I've heard for putting a mini in a CC and keeping the original CRT and thus the form factor intact. An easy test would be to put the 575 yoke on the CC CRT and see if I can still adjust the video to fit the 10" CRT. Cool. This is a much better idea than tapping into the CC's analogue board video circuits. Even if you could get it to work, you'd be burning so much more energy and creating that much more heat than necessary powering a non-existent logic board, hard drive, etc. just to run the CRT.
I believe it's any 13" or 14" Apple trinitron monitor's AB and yoke - AFAIK all 12" Apple monitors were shadow mask (not trinitron), and their AB's delivered 512x384, not 640x480.
But any 640x480 trinitron AB/yoke should work.
In my experience there were two issues with this sort of setup:
(1) because the yoke has to be moved closer to the front of the CRT, it's difficult to get the full width of the screen to display. The width is similar to what you get with the VGA mod to most Color Classics - acceptable but not totally to the left and right edges.
(2) the little ribbon cable that goes from the AB to the underside of the video board (the metal-box-encased board at the end of the CRT neck) is shorter on the Mac Color Display than on the CC's original AB. So it's a little tricky figuring out how to position - and, more to the point, secure - the new AB inside the CC case while ensuring that the AB-to-video board connection doesn't come loose.