(Edit: adding disclaimer: I should make it clear this is not due to lack of information on JDW's video. He covered it at 7:15 of the video, but I'm an idiot and even though I watched the whole video when it first came out, I skipped ahead to the action when I went to go watch the steps today when I went to modify the board. It's mainly a cautionary tale to not be an idiot and to fully understand a mod before performing it. )
Unfortunately, I may have flown a little too close to the sun with my modding of my color classic. I followed JDW's video for doing the mod. I had no jumper at J78 (Maybe because I have a Rev D board?). But I followed all the other steps in his walk through. I confirmed the isolation of pin 25. Added jumper between 20 and 24. I also did the horizontal deflection voltage by isolating one pin (pin 8?), then adding a jumper to the other pin (pin 12?).
Well, when I went to power on the machine, I get no picture. The boot process works properly - start up chime, beep for bad date/time, responds to volume up/down, etc. Unfortunately, screen is black. I can hear the CRT fire up on boot, but no image. I checked the connections to the analog board. CRT anode cable is in there securely.
Then I thought back to the fact that I have no jumper at J78. And I realized my mistake. Hoping that I hadn't fried anything on the analog board, I did a quick search and realized, on boards with no J78 jumper, you have to isolate pin 20 differently (see https://colourclassicfaq.com/general/vga.html)
So, I took everything apart, cut the trace connecting pin 20 to the common trace that goes along the edge of the board (and used to be connected to pin 25, before we isolated it). Fortunately, since these are for the sense lines, I was hopeful nothing was permanently damaged. I put some solder mask on the cut and reassembled.
Powered up after isolating pin 20 and I have an image again! And a 640x480 one at that.
So, word of caution - if you have a color classic Rev D board with no jumper at J78, make sure you isolate pin 20!!!
I'll drop a comment with this info in JDW's video to hopefully spare others the momentary heartache I felt when I thought I had destroyed my Color Classic.
Unfortunately, I may have flown a little too close to the sun with my modding of my color classic. I followed JDW's video for doing the mod. I had no jumper at J78 (Maybe because I have a Rev D board?). But I followed all the other steps in his walk through. I confirmed the isolation of pin 25. Added jumper between 20 and 24. I also did the horizontal deflection voltage by isolating one pin (pin 8?), then adding a jumper to the other pin (pin 12?).
Well, when I went to power on the machine, I get no picture. The boot process works properly - start up chime, beep for bad date/time, responds to volume up/down, etc. Unfortunately, screen is black. I can hear the CRT fire up on boot, but no image. I checked the connections to the analog board. CRT anode cable is in there securely.
Then I thought back to the fact that I have no jumper at J78. And I realized my mistake. Hoping that I hadn't fried anything on the analog board, I did a quick search and realized, on boards with no J78 jumper, you have to isolate pin 20 differently (see https://colourclassicfaq.com/general/vga.html)
So, I took everything apart, cut the trace connecting pin 20 to the common trace that goes along the edge of the board (and used to be connected to pin 25, before we isolated it). Fortunately, since these are for the sense lines, I was hopeful nothing was permanently damaged. I put some solder mask on the cut and reassembled.
Powered up after isolating pin 20 and I have an image again! And a 640x480 one at that.
So, word of caution - if you have a color classic Rev D board with no jumper at J78, make sure you isolate pin 20!!!
I'll drop a comment with this info in JDW's video to hopefully spare others the momentary heartache I felt when I thought I had destroyed my Color Classic.
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