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Post by mirkosoft on Sept 15, 2015 19:40:06 GMT
Hi! I'm using few converters for VDC display, also C1084 monitor - but only for lightpen/gun input. I tried to adjust VDC colors as good as possible and result is not good extremely in case of dark yellow. Converter cable created Robert Willie (aka Hydrophilic) - so, you Robert maybe can help... Here are images: ![]() original  result:  result of VDC palette:  VDC color test original (VICE)  and result:  and last is 256 color test:  Can anybody explain me what to adjust? Thank you for each idea. Miro |
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Post by Pyrofer on Sept 16, 2015 16:54:33 GMT
Your image links don't work?  |
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Post by mirkosoft on Sept 16, 2015 17:00:12 GMT
I'm sorry, I forgot to leave it on my domain... they're back!
Miro
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Post by Pyrofer on Sept 16, 2015 23:35:50 GMT
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Post by gsteemso on Sept 17, 2015 18:25:16 GMT
In response to… I’m not even going to try to spell that on an iPad! …“the previous poster:” Based on the screenshot you linked us to, your homebrew converter gives absolutely beautiful results, with one exception—light black is indistinguishable from dark black. Do you have any plans to improve on that?
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Post by Pyrofer on Sept 17, 2015 21:35:38 GMT
Ok, the previous poster was me. I appear to have had an accident with my account and the display name, it is now fixed. Sorry. Yes, the "Light black" or "Dark Grey" is indeed just black. I tried quite a few combinations of resistor values to try and fix that but failed. I don't know if I can fix it by just tweaking resistors or if I need to redesign the circuit, so for now I just ignore it. I am working on another board that converts the 80 col signal to S-Video instead of RGB (as it seems America never had scart and all have S-Video sockets instead). So Maybe I will try and get it corrected for that version. Also, calling it a "homebrew" adapter feels a little under stating it. I will let you decide how good quality you think it is from the photo of a finished and assembled board,  |
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Post by gsteemso on Sept 19, 2015 6:41:59 GMT
"Homebrew"-ness is orthogonal to build quality. Your board looks very slick and professional -- and since you designed and built it yourself, therefore it is homebrewed.
I'll be interested to see if you can come up with an S-video converter that gives equally good results. As I understand it, Commodore didn't do that in the first place because it would have been prohibitively expensive to make a signal clear enough to be legible on a 1980s TV set in 80 columns. Obviously the technology is much better now, but at the same time, current development stopped being about SDTV video nearly a decade ago.
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Post by Pyrofer on Sept 19, 2015 20:01:36 GMT
I just got it pointed out to me that due to a "logic error" the Light black would never work. So that is just how my board is. If I redesign it I can fix it, but no tweaking will change that on the existing boards.
There is a common chip now that does RGB to S-Video and Composite. That is the one I will be using. I have to integrate the CGA to RGB I already have to supply the RGB to S-Video chip. I will try to fix the mistake with Light black (dark grey) at the same time. It seems I have to start from scratch with the board or put up with that same colour still missing.
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Post by hydrophilic on Sept 21, 2015 6:40:14 GMT
@pyrofer, your board looks very professional... sad it suffers from the black = d.gray problem (my first RGB->Svideo circuit did too!). @mircosoft (OP), it looks like you suffer from the "dark yellow problem". The simple boards that I have built (and published for free) render RGBI = 1100 as dark yellow... the original 1902 / 1084 monitors had a special circuit to change this "dark yellow" into brown (like your 1st photo shows). To fix this problem, you would need either a pair of Quad-NAND chips, or a "decoder" chip (like 74LS138)... see this image for example (I have not tried, but think it should work). |
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Post by Pyrofer on Sept 21, 2015 15:07:48 GMT
@hydrophillic, Yes. I used the decoder chip solution on mine for the brown fix. Sadly due to the logic method I used for the I lines I can't ever have the light black working on this design.
It's published too, I put it up on postimg as a schematic if anybody is interested.
John Carlson has the best solution I have seen (very simple too) and is currently selling them, they have near perfect colours, the brown fix AND light black all working.
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