Help with Composite out

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bwinkel67
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Re: Help with Composite out

Postby bwinkel67 » Mon Feb 03, 2020 10:19 pm

Thank you again Martin for the helpful information. I've been trying various different TV/monitor combos. Basically any LCD TV/Monitor that has HDMI, VGA, and composite, I have tried...they are all about the same small size. Two Toshibas (one with DVD and one just a TV/Monitor) and one Emerson (with DVD). I will say, I feel bad now calling the SuperSonic a cheap LCD TV/Monitor because it actually gives the best picture...the crispest and I can't wait to see what VGA and HDMI from another computer looks like. The others don't give too clear a picture even in F2 color-composite mode -- not crisp for a picture that is supposed to be the best quality for non VGA/HDMI mode. The simple Toshiba TV/Monitor can't even do a good job with F2 color-composite mode as it flickers in the upper right hand corner in 30 second interval. The two Toshiba's can actually show color-composite in F1 mode but the Toshiba TV/Monitor/DVD one has a dimmer picture and the Toshiba TV/Monitor flickers every 30 seconds...but they both show it in color which is not what the SuperSonic does. The Emerson just shows a blue screen basically saying "uh, no way am I able to show this picture."

So yes, F1 color-composite actually is showing color and it's just that I don't have a monitor that can handle the PAL-like signal. I'm actually happy I stumbled on this little SuperSonic monitor now on FreeCycle (a US website to give free stuff away) as getting composite compatibility that's quality isn't guaranteed.


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bwinkel67
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Re: Help with Composite out

Postby bwinkel67 » Thu Feb 06, 2020 4:44 pm

So I found this diagram with instructions which seem perfect:

https://www.retrocomputershack.com/SCART-DESIGNS/Sinclair-QL/index.html

Specifically the connector diagram:

RGB_SCART.png


And the specific line on pin 1:

pin1_blanking.png


So first off, this seems to be talking about how SCART that comes built-in to a monitor operates with regard to SCART pin 20 having high or low voltage causing SCART (and thus the monitor) to either go into composite or RGB mode. I suppose, perhaps, with the US model having the DIN-8 pin 1 (which is used on SCART pin 20) be a constant 5 volts, that makes more sense for building cables like that since the signal is guaranteed to be above the low voltage and even above the high of 3 volts in the description which then forces SCART to pick RGB mode. So if anyone ever tried to hook a US QL to a monitor in the UK that supported both composite and SCART, the US QL would only show a proper RGB signal on that monitor and avoid composite since otherwise it would feed an incompatible NTSC signal to it causing the image to scroll (that is my hypothesis as to why US RGB is different from UK).

Some questions:

  • Am I reading that correctly with regard to SCART going into the two different modes?
  • I'm guessing here that the US models kept the signal high at 5 volts to force the RGB mode.
    • Does that seem like valid reasoning as to why the US was forced high (i.e. trying to solve that mystery)? -- with no PAL in US market at the time and no one likely thought of LCD monitors that could handle both in the distant future so the US RGB was re-designed with the high signal only so that SCART would always choose RGB mode?
  • For making a DIN-8 to SCART cable where the SCART only goes into an upscaler, does the blanking signal still matter?
    • Do upscalers make the same internal decisions that SCART monitors made or is it dependent on what type you have (I have a cheap SCART to HDMI for instance)?


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bwinkel67
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Re: Help with Composite out

Postby bwinkel67 » Thu Feb 06, 2020 7:40 pm

I have a bunch of these cheap up/down scalers (av2vga, av2hdmi, hdmi2av, hdmi2component):

51-bdzfCl5L._AC_SX425_.jpg


I tried to use my color-composite to go from av2hdmi. The results weren't good. The picture was also black&white with lots of interference where the interference actually added little specs of color everywhere. It reminded me of watching a black&white TV show from the 60's on a bad color TV where it can't avoid some color adding.

So it was a bad color picture that didn't use the color of the source. It did show, for one second, a solid red and white image on booting to F1 but then the monitor just said "nope" and went to its dislike for the color-composite signal on my machine.

So I can't use the AV (color-composite) to upscale to HDMI or VGA. I just got an inexpensive SCART-to-HDMI one but am still waiting for a male SCART connector so I can make that RGB-to-SCART cable and then will see what sort of image I get.

So mostly I am staying with the monochrome-composite because it's just such a beautifully crisp picture. I feel like I have a Mac SE again only with a better picture since that didn't even do grey scales :-/


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Re: Help with Composite out

Postby Derek_Stewart » Thu Feb 06, 2020 8:09 pm

Hi,

I have a Retroshack SCART cable for the QL, which uses the QL RGB connections, it gives a nice display on a SCART based TV, but in monitor mode there are columns missing due the tge QL overscan.

I thought a SCART to HDMI converter would do tge job, but I have tried many of these SCART2HDMI converters with a Retroshack QL SCART cable.

Which some worked, but did not display all the QL monitor mode display and others did not work at all. I got the money paid refunded.

I use a Jammer GBS8220 RGB to VGA board which work better.

I think we need a dedicated VGA port like on the Q68...


Regards,

Derek
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dilwyn
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Re: Help with Composite out

Postby dilwyn » Thu Feb 06, 2020 10:34 pm

Derek_Stewart wrote:Hi,

I have a Retroshack SCART cable for the QL, which uses the QL RGB connections, it gives a nice display on a SCART based TV, but in monitor mode there are columns missing due the tge QL overscan.

I thought a SCART to HDMI converter would do tge job, but I have tried many of these SCART2HDMI converters with a Retroshack QL SCART cable.

Which some worked, but did not display all the QL monitor mode display and others did not work at all. I got the money paid refunded.

I use a Jammer GBS8220 RGB to VGA board which work better.

I think we need a dedicated VGA port like on the Q68...

With all our discussion on the problems with QL to monitor video signals and wiring, I think it will guarantee Marcel huge sales of his QL-VGA device when he manages to get it into production.

The attractions of a dedicated VGA monitor connection are pretty obvious to us all now I guess.


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Re: Help with Composite out

Postby Martin_Head » Fri Feb 07, 2020 11:39 am

I would say that if you want a clean, crisp colour display from a QL. Forget about the colour composite signal entirely. And use the RGB signals converted to whatever you need.

I have not tried to connect a QL to a modern LCD TV. But I was wondering, if you put the TV into the 4:3 aspect ratio mode, rather than the wide screen 16:9. So you get black bars on either side of the screen. Are the the characters at the ends of the lines still lost?


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Andrew
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Re: Help with Composite out

Postby Andrew » Fri Feb 07, 2020 11:52 am

Martin_Head wrote:I have not tried to connect a QL to a modern LCD TV. But I was wondering, if you put the TV into the 4:3 aspect ratio mode, rather than the wide screen 16:9. So you get black bars on either side of the screen. Are the the characters at the ends of the lines still lost?

Yes (in monitor mode)


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bwinkel67
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Re: Help with Composite out

Postby bwinkel67 » Thu Feb 13, 2020 10:36 pm

So my RGB-to-SCART cable came in today. It cost $2.95 (looks like they just added 50 cents shipping) and is for the Sega Master's System:

https://www.ebay.com/itm/RGB-AV-TV-Cable-Lead-Cord-Scart-1-8m-For-Sega-Mega-Drive-1-Genesis-Master-System/233380795198

It's not quite compatible with the QL's connector as the Sega even uses different pins for color:

megamstr.png
megamstr.png (3.56 KiB) Viewed 276 times


So I took apart the cable. The SCART plug luckily just snapped apart though the top thumb screw was fake (I had a female connector that came apart and the thumb screw held it together) and is easily solderable:

SCART-case.jpg


SCART-connector.jpg


So the DIN-8 though was weird. I had to cut if apart since it was molded on. Having done that with the QL power connector I know that if cut carefully that I can use Crazy Glue to close it up again and it will hold and look nice. I didn't expect to find a big blob of glue-stick neatly molded inside of the outer casing and covering all the wires...had to cut that off.

DIN-8.jpg


So now I'll create the QL RGB-to-SCART cable according to these instructions:

https://www.retrocomputershack.com/SCART-DESIGNS/Sinclair-QL/index.html

If I want to also add diodes on the DIN-8 end, anyone know what type I should use?


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bwinkel67
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Re: Help with Composite out

Postby bwinkel67 » Sun Feb 16, 2020 8:41 pm

Still in search of that color monitor picture. I finally built my cable to spec and tried it on this:

scart2hdmi.jpg


Well, I got a faint image that looked like a grey scale embossing. So I figured it likely was trying to take the Composite CSYNC and display it as composite.

To test this I tried this:

av2scart.jpg


But coudn't get it to work. They had sent the wrong one and instead of in/out switchable they sent it only in one direction. As it turns out it was in the out direction so pins 19/20 for video were swapped and so were 1/2 and 3/6 for audio. A quick re-solder and voila, finally got an HDMI picture via composite and as suspected, the SCART-to-HDMI is merely one of these in a different connector:

av2hdmi.jpg


Cost about the same so now I have 2 things I can't use. I think my RGB-to-SCART cable works but I just need to get a "real" SCART-to-HDMI converter. It seems one of these might be more legit:

scart2hdmi-real.jpg


You can get them for about $24 on eBay. Any particular place I should look for or are the all about the same? Trying to avoid getting another dud.


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mk79
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Re: Help with Composite out

Postby mk79 » Sun Feb 16, 2020 10:40 pm

bwinkel67 wrote:You can get them for about $24 on eBay. Any particular place I should look for or are the all about the same? Trying to avoid getting another dud.
They all look the same but they are definitely not. Not only that, Tobias has one that works for him that doesn't work at all for me. So no, there is no sure way to know what you're getting and I was so tired of trying that I created the only dedicated QL solution with QL-VGA. Problem is, I'm not selling it yet ;)
dilwyn wrote:With all our discussion on the problems with QL to monitor video signals and wiring, I think it will guarantee Marcel huge sales of his QL-VGA device when he manages to get it into production.

The attractions of a dedicated VGA monitor connection are pretty obvious to us all now I guess.
I've spent a few painful hours this weekend soldering RGB cables and pin headers (QL-VGA comes with everything needed except an USB power supply and a VGA cable). The main problem is now Corona-Virus related: on Wednesday after a long pause my preferred PCB house started taking orders again, which I quickly did. Today they announced out of the blue that they stopped accepting orders for SMD assembly again but that the orders that are already placed will be fulfilled, albeit with 1-2 weeks delay. So that gives me some hope that they will arrive eventually (they applied the solder mask to the boards 3 hours ago, so stuff is happening). I ordered 30 PCBs but only have 20 FPGA boards and cables, so currently I can do 20 QL-VGAs. The problem then is that I ordered some parts for another project 2-3 weeks ago and they still haven't shipped yet (usually it takes 1 day), absolutely nothing seems to ship currently from China, so it's unclear when I can stock up on FPGA boards etc again. I've sourced a few other parts from Europe but these can in some instances cost 3-10 times more.

Cheers, Marcel



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