Macintosh Color Classic 640x480 Video

[rvp]

Hello guys, I recently did a video upgrade soldier to my Macintosh Color Classic. It seemed to go very well except for one thing. My monitor is now goes from big on bottom and top and narrow in the middle. I am not sure if I am describing it correctly.

The system 7.5.3 says that it is in the 640x480 at 67 Hz, which is what is suppose to be. I tried to adjust this problem, however, the PB will not move enough to fix it. Has anyone over the years done this upgrade to the Macintosh Color Classic. Let me know if you had this problem or if you were able to fix it. I tried every little pin hole on the back to adjust, but nothing has made a big difference.

 

[bluekatt]

wrong forum this needs to go in to the compact forum

and what you did was a takky upgrade or at least tried to do it http://www.colourclassicfaq.com/general/vga.html

 

[rvp]

It was not a takky upgrade I did try the listed website recommendation. However, I used:

http://www.ipod-repair.com/instructions/CC_Video_upgrade/index.html

Everything seems fine except for the ugly squeeze problem.

 

[equill]

Whether your intention was a 'Mystic' or a 'Takky' upgrade, there is a hosted forum about Colour Classics within Applefritter that has answers to more questions than you have yet thought of. I recommend that you look there for answers to your display geometry problem.

de

 

[tmtomh]

I agree with others about the other forums dedicated specifically to CC-related mods.

That said, if I gather correctly, your screen display now looks a bit like an hourglass, yes?

There are two possible causes:

(1) It's a built-in limitation of the CC video circuitry; there just isn't enough voltage to make the entire display occupy the full width of the CC's CRT monitor once you do the 640x480 upgrade. If the "squeezed" middle portion of the display isn't too narrow, then you can simply adjust the CC's picture so that the top and bottom are the same width as the middle.

(2) Related to the above, you may also be seeing barrel distortion (or in this case, inverse-barrel distortion). Using the same adjustment mentioned above, you may be able to straighten out the sides of your display image while making the squeezed center portion wider.

I have to say, though, that it's probably more likely that scenario #1 is true - that is, in many CC VGA mods, one is limited by the width of the middle portion of the screen display.

Some folks have solved this by installing an extra capacitor in a certain place on the analog board, but others have said even that doesn't make much of a difference.

Good luck!

Best,

Matt

 

[rvp]

Thanks for both of your help. I will try to adjust, but I guess the power thing makes sense. Do either of you if it is possible to reset the monitor so the whole thing will be "factory." Maybe that might not even help. What do you think?

 

[Quadraman]

I read an article once about someone who experimented with 800x600 on a CC and got it to work, but only for a few minutes before he switched it back to 640x480. It might be possible that a CC can higher than 640x480 from this, but this guy didn't want to risk blowing up his video hardware, so someone else will have to be brave and try 800x600 for a longer test period to see if it is stable.

 

[tomlee59]

Google for "colour classic" and "pincushion distortion." The latter is the complement of barrel distortion (fat in the middle). Stuart Bell's site is likely a good starting point as well.

 

[Mac128]

In my experience this is the pin-cushion effect. Please indicate which sources you used to modify your CC video as most have a very detailed adjustment section, which is all this should be. I have performed two different methods of the video mod and in both cases had to make substantial adjustments to the CRT. I do not recall if all were controlled by the rear controls or if there were others as well. Check the http://colourclassicfaq.com/ which should have the adjustment details for you to double-check. This and many other sources around the net should provide all the information you need to thoroughly troubleshoot common issues.

 

[rvp]

I used:

http://www.ipod-repair.com/instructions/CC_Video_upgrade/index.html and followed all directions in order to modify the color classic screen. I get the resolution, but yes with that pushpin effect. I followed the ending directions from the site to adjust the pushpin screen and moved it side to side. I was only able to get it so far before I could not move the little circle party anymore, also, I tried the other-way and then it would stop. It is like the monitor is at the max, but the picture does not show it like that.

Another thing I feel as if the video is in the middle, but the screen is still has "available black around it." There is just no picture going into the extra black section. I will try to play around more. I wonder is their away to reset the monitor to the "default"

 

[ChristTrekker]

http://www.ipod-repair.com/instructions/CC_Video_upgrade/index.html

Geez, reading that page made me more scared than ever to try that hack.

 

[tomlee59]

I used:
http://www.ipod-repair.com/instructions/CC_Video_upgrade/index.html and followed all directions in order to modify the color classic screen. I get the resolution, but yes with that pushpin effect.

Not all CCs are candidates for this upgrade. Remember: You are modifying the unit beyond its designers' original goals, so your mileage may vary. At minimum, you may have to abandon the idea of obtaining full screen size. First adjust the PB control until you have the least pincushion (not pushpin) distortion. Then reduce the width until the distortion is tolerable. The result is the best that you can get with the controls that are available. If the result is still not to your liking, you'll have to revert to the unmodified state.

The pincushion circuitry can probably be modified to provide larger correction range, but without a schematic, it's a bigger job than most will want to tackle. Years ago, I promised Stuart Bell that I'd provide him with a schematic. Naturally, I still haven't gotten a round tuit (although I desperately wanted one for Christmas), so that project remains to be done (along with countless others)...