Author Topic: No RGB via SCART cable?  (Read 1316 times)

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Offline arkive

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No RGB via SCART cable?
« on: 19:42, 15 September 19 »
Hi guys, just got a 6128 with Gotek. No monitor, I use consumer CRT TV (Trinitron) as a display.

The computer came with a DIY PSU / TV cable combo. PSU is an old PC one, it connects to the TV cable via female socket. The TV cable has 3 inputs on Amstrad's side (5V, Monitor 6-pin DIN and audio jack) and SCART on the TV side.

Everything works fine with one niggle, quite big one for me. Im pretty sure that the picture displayed on my TV is not true RGB, or a borked one somehow. It looks a bit like S Video might - better than Composite but not 1:1 RGB quality. It looks worse in some cases (glowing pixels/colours?) and better in others.

Now, I never had an Amstrad before, so this is a guess estimate of course. My point of reference is my general experience displaying other systems with RGB IQ quality (I use Raspberry Pi with Pi2SCART RGB hat and also some other original micros). The display of the emulated Amstrad looks better than the original one (true RGB). EDIT: I just realised that RPi outputs 270pix vertically. So the image is taller - perhaps it makes it looks better, becasue of pixel separation? Now I'm well and truly confused :/

I'm not much of a technical person but from what I read I suspect that the cable might be either damaged or badly made to start with, kinda like this guide says: http://www.cpcmania.com/Docs/scart/scart.htm

I was hoping somebody my comment on this situation. Am I imagining things? Is it possible that Amstrads'diaplay looks worse on consumer TV because it was meant for monitors?  Should I dismantle the cable and investigate? Not sure what to look for though...

I link to some photos of the display from Amstrad and RPi emulated for comparison. Any help would be most appreciated.

https://postimg.cc/gallery/325dhqvsc/

Offline Gryzor

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Re: No RGB via SCART cable?
« Reply #1 on: 21:06, 16 September 19 »
Can't see the images on my phone right now and can't type much in terms of help right now, but I just wanted to comment that the CPC monitor is, in fact, a TV minus the modulator.

Offline Token

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Re: No RGB via SCART cable?
« Reply #2 on: 22:32, 16 September 19 »
Hi
It should be much sharper with clear scanlines. Like with a ST, Amiga, Megadrive etc.Maybe it can be fixed since the TV setting, I don't know, the signal could be a bit hot on RGB line or sync, experts should answer soon ;) 

Offline tjohnson

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Re: No RGB via SCART cable?
« Reply #3 on: 23:56, 16 September 19 »
The cpc can't output in anything other than rgb can it so it had to be rgb but the quality might not be that great, maybe the cable is off poor quality.

Online SkulleateR

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Re: No RGB via SCART cable?
« Reply #4 on: 00:25, 17 September 19 »
Sometimes it´s also "fault" of the TV .... I´m using RGB on a 70cm TV and also on an old 13 inch (dunno cm right now) commodore monitor, comparing those two pictures (same computer, same cable) the little commodore Monitor always wins ;)


the resolution is the same, so if the screen is smaller the picture is quite a bit more "sharp" in my eyes

Offline Bryce

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Re: No RGB via SCART cable?
« Reply #5 on: 09:30, 17 September 19 »
The cpc can't output in anything other than rgb can it so it had to be rgb but the quality might not be that great, maybe the cable is off poor quality.

Not quite true. There's a monochrome composite picture on the LUM line. But that's not what he's seeing as he has colour.

Bryce.

Offline tjohnson

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Re: No RGB via SCART cable?
« Reply #6 on: 15:09, 17 September 19 »
Not quite true. There's a monochrome composite picture on the LUM line. But that's not what he's seeing as he has colour.

Bryce.


Very good point

Offline arkive

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Re: No RGB via SCART cable?
« Reply #7 on: 22:35, 18 September 19 »
Thanks for all the replies. And apologies for wasting your time with what turned out to be a textbook  :picard: :doh: example.

I fired up the CPC once again yesterday, to take a few more pics and had an inkling to mess with the TV's settings. Bringing down the contrast from ~90 to ~50 has cured the malady. All is as it should be, pixel-perfect RBG reigns supreme.

It seems like a completely ridiculous thing to miss (and it was for sure), but it just never occured to me it could be the reason. All my other consoles/RPi emus are calibrated for high contrast and look good this way. Plus I did try to bring it down before with CPC, but only a little bit.

In any case, I'm elated because I was just about to go on a wild goose chase, ripping up cables, buying new ones, perhaps even sending the unit off for repairs...nightmare scenario. So, here's the CPC/Trinitron/RGB  version of me, now: