Yeah, I recognized the scan rate and greyscale issues as separate, although it does seem there is some kind of sync signal in the video signal itself, perhaps to signal video start/stop or line start/stop? I don't really know since I only know a very basic concept as to how CRTs work.
What I've tried is desoldering only the video input wire from the analog board and then tweaking the voltage up/down. Without a video signal, there is raster and the screen is bright white, but there are bright tilted horizontal lines. I think it's bright white because 5V = white and 0V = black. If I ground the video input, the screen goes completely blank. When feeding just a DC voltage, below 1V the screen is blank and over 2V the screen is at full brightness. Between 1-2V, the brightness varies directly with the voltage.
I tried disconnecting the analog board from the logic board and connecting it to my laptop's VGA output. I was curious if the analog board would have any response to my laptop's HSYNC and VSYNC in VGA mode. Unfortunately, I didn't even get raster, just a blank screen. I think if it could recognize the sync signals at all, it should display some kind of raster like it does when hooked up to the logic board. Is the polarity of the sync signals different than VGA?
I've seen the poor man's greyscale project. It's a pretty cool idea, but seems like a lot of work from a mechanical standpoint to retrofit all that to fit, and I also would hate to waste a perfectly good monitor just to use its parts. I've also seen some people buy a 9" Point Of Sale monitor and transplant all its guts into a classic Mac to get the VGA greyscale. It would be slicker, easier (at least mechanically), less wasteful, and cheaper to use all the original parts, if possible.
What I've tried is desoldering only the video input wire from the analog board and then tweaking the voltage up/down. Without a video signal, there is raster and the screen is bright white, but there are bright tilted horizontal lines. I think it's bright white because 5V = white and 0V = black. If I ground the video input, the screen goes completely blank. When feeding just a DC voltage, below 1V the screen is blank and over 2V the screen is at full brightness. Between 1-2V, the brightness varies directly with the voltage.
I tried disconnecting the analog board from the logic board and connecting it to my laptop's VGA output. I was curious if the analog board would have any response to my laptop's HSYNC and VSYNC in VGA mode. Unfortunately, I didn't even get raster, just a blank screen. I think if it could recognize the sync signals at all, it should display some kind of raster like it does when hooked up to the logic board. Is the polarity of the sync signals different than VGA?
I've seen the poor man's greyscale project. It's a pretty cool idea, but seems like a lot of work from a mechanical standpoint to retrofit all that to fit, and I also would hate to waste a perfectly good monitor just to use its parts. I've also seen some people buy a 9" Point Of Sale monitor and transplant all its guts into a classic Mac to get the VGA greyscale. It would be slicker, easier (at least mechanically), less wasteful, and cheaper to use all the original parts, if possible.