Good thought on the phase-locking techknight. I just did a quick test running the AB from a free-running oscillator at (approximately) the same frequency and duty cycle, while driving the yoke from the actual HSYNC signal. The result isn't terrible, but there is a faint vertical ripple that passes periodically through the image from left to right, maybe only 1mm but noticeable because of the motion.
Given that there's not too much distortion of the image otherwise, it makes me think that any reasonable phase locking strategy may be good enough. Given what the flybacks are rated for, one interesting possibility would be to move the flyback frequency downward (say 15-20kHz) if that produces an easier phase lock. On the other hand, that might require reducing the drive voltage or it could fry something. Has anyone tried NTSC scan rates on this circuit?
jt, the plan is to get an SE/30 video card eventually. Recently I bought an SE with a Radius TPD card which I was hoping would be my first testbed, but sadly the card doesn't seem to work. Here's the TC thread about that: https://www.thinkclassic.org/viewtopic.php?id=642
Another idea would be to overclock the SE/30 and/or hack the video circuit, which conveniently is a bunch of discrete components. I think the amount of onboard VRAM might support 640x400 at 1 bit. But I haven't really thought that through yet. One hack at a time.
Given that there's not too much distortion of the image otherwise, it makes me think that any reasonable phase locking strategy may be good enough. Given what the flybacks are rated for, one interesting possibility would be to move the flyback frequency downward (say 15-20kHz) if that produces an easier phase lock. On the other hand, that might require reducing the drive voltage or it could fry something. Has anyone tried NTSC scan rates on this circuit?
jt, the plan is to get an SE/30 video card eventually. Recently I bought an SE with a Radius TPD card which I was hoping would be my first testbed, but sadly the card doesn't seem to work. Here's the TC thread about that: https://www.thinkclassic.org/viewtopic.php?id=642
Another idea would be to overclock the SE/30 and/or hack the video circuit, which conveniently is a bunch of discrete components. I think the amount of onboard VRAM might support 640x400 at 1 bit. But I haven't really thought that through yet. One hack at a time.