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I have added and removed capacitors and resistors from the output, hasn't made any difference.. If it was ringing or drive issues, then it should have changed something lease..stephen_usher wrote: 29 Nov 2018 17:57 Is it just me or does that look like an analogue issue on the output? Almost as if it's a "ringing" feedback?
The fact that it takes a while from the top of the screen for the white to fade up to white in the scan lines makes me think that there's a power issue of some kind where something has to charge up before "white" can be displayed, which takes a few scan lines to do.
stephen_usher wrote: 29 Nov 2018 18:56 I know this is about a composite video issue, but it does seem possibly similar...
http://www.notanon.com/page/2/
Could the DAC's output be too weak to drive the video directly?
Theres transistors already on the MB, I did wonder that, but probably end up a lot of messing about :( If we heading towards buffering the DAC, then might as well just stick with the original RGB circuit :roll: .stephen_usher wrote: 29 Nov 2018 19:53 Can you add transistors controlled by the DAC output but driving a higher power source? I'm guessing that those using a breadboard could test this.
Makes sense, like the signal takes a dive when going over a certain threshold. You could try to amplify this by displaying a picture of the right half of a pyramid in 2D. You know, a line running from the top left of the screen to the bottom right and the screen one side of the line being black. This causes the amount of black increasing gradually by each line.exxos wrote: 29 Nov 2018 19:45 It does almost seem like a power issue where it can only manage to draw the white areas when there is 50% black (text) with it also.
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Did you see the diagnostic cart tests Icky did ?sandord wrote: 29 Nov 2018 20:02 Makes sense, like the signal takes a dive when going over a certain threshold. You could try to amplify this by displaying a picture of the right half of a pyramid in 2D. You know, a line running from the top left of the screen to the bottom right and the screen one side of the line being black. This causes the amount of black increasing gradually by each line.
Yeah. Though not quite what I mean, still interesting.