I am in the process of doing the VGA mod on my CC. I have an LC 575 motherboard that I want to use as well.
First I isolated pin 8 with a dremmel type tool. Then I soldered a wire from pin 8 to pin 12.
I then Isolated pin 20 on the analog board by dremmeling the pin in this manner:
22 20 18
21 | 19
| I cut right there, figuring it would be isolated
I then dremmeled pin 25 at the bottom (towards the connector) to isolate that (or so I assumed). I then soldered pin 20 to (d'oh) pin 26. I got video, but it was really messed up, and the OS 7.6 boot CD gave me a bomb (bus error) with the LC 575 motherboard. Noticing I didn't solder pin 20 to pin 24 I dove in again to fix that.
I then soldered pin 20 to pin 24 with some wire and put everything back together. I now have NO video...
Here's what I thought might have caused it:
1) pin 25 is not isolated because I only isolated it on the bottom, not the bottom and top as pictured here:
2) I messed up the solder joints surrounding pin 26 through pin 18 as I did get solder very hot around there. I didn't have the right tip on the first time. I DID find my fine tip though...
3) I broke the CRT in some manner...
I've checked to make sure I plugged everything in. I just don't know where else to check, or how to check if I've killed my color classic.
Any tips or advice is appreciated!