A1200 RGB SCART to HDMI issue

[Geon106]

Hey all,

So I've set my A1200 back up and have a different tv for it, a 42" Samsung 3D FHD LED panel. I was using a smaller 22" logik led tv in my bedroom previously.

Before I was using an RGB to SCART cable from Amiga Kit, this was in connected to a SCART to mini scart adapter. This worked great.

I tried with the newer tv and get just a black screen. I tried another cable from Amiga Kit but issue remained. I purchased a scart to HDMI scaler (https://www.amazon.co.uk/gp/aw/d/B01...yAL&ref=plSrch) and just get a grey screen with very faint outlines of icons.

So it seems this up scaler doesn't like the RGB signal or isn't decoding it properly.

I tested the Amiga on my old TV using just the RGB to SCART and this works fine so the Amiga is outputting fine.

My query is, is there a fix or is there a specific type of SCART to HDMI adapter/scaler I need to buy?

[Daedalus]

It's possible that the adaptor simply doesn't support RGB, or that the TV doesn't support it.

SCART uses a couple of voltages to tell the display what format to use (widescreen/4:3, composite/RGB etc.) In old cables these voltages were way off, but old TVs didn't care and showed the image anyway. Newer TVs are more fussy about the specification, so resistors are usually added to the SCART cables to compensate. This is likely the story with the cable you currently have from AmigaKit. The problem with this approach however is that it depends on the impedance of these switch signal inputs to be within a certain range; if they're not, the voltages can go out of spec, leading the TV (or scaler) to misinterpret the signal or refuse to show anything. This could be what's happening. If that's the case, two possible fixes are:

- measure the voltages of the switching signals and replace the resistors with alternative values to produce the correct voltages for your specific TV/adaptor;

- build more sophisticated voltage control circuits with a couple of resistors and Zener diodes.

[Geon106]

Originally Posted by Daedalus

It's possible that the adaptor simply doesn't support RGB, or that the TV doesn't support it.

SCART uses a couple of voltages to tell the display what format to use (widescreen/4:3, composite/RGB etc.) In old cables these voltages were way off, but old TVs didn't care and showed the image anyway. Newer TVs are more fussy about the specification, so resistors are usually added to the SCART cables to compensate. This is likely the story with the cable you currently have from AmigaKit. The problem with this approach however is that it depends on the impedance of these switch signal inputs to be within a certain range; if they're not, the voltages can go out of spec, leading the TV (or scaler) to misinterpret the signal or refuse to show anything. This could be what's happening. If that's the case, two possible fixes are:

- measure the voltages of the switching signals and replace the resistors with alternative values to produce the correct voltages for your specific TV/adaptor;

- build more sophisticated voltage control circuits with a couple of resistors and Zener diodes.

Hmm. I wouldn't know how to do either of them. I've ordered another scaler to try but otherwise I'll just use the old smaller tv as that does accept the RGB signal

[Daedalus]

Fair enough, let us know how it goes! Model numbers would be useful for the different scalers to let others know what works or doesn't.

[Geon106]

Originally Posted by Daedalus

Fair enough, let us know how it goes! Model numbers would be useful for the different scalers to let others know what works or doesn't.

Sorry I'm not very good at circuitry and making custom wires etc.

Once the other scaler is delivered today and test before reporting back my findings

[Daedalus]

Originally Posted by Geon106

Sorry I'm not very good at circuitry and making custom wires etc.

No, nothing at all to apologise for, don't worry Most people are the same - connect things up and enjoy using them rather than building and modding things. Hopefully your new scaler works well, and that can help others in the same situation.

[Geon106]

Originally Posted by Daedalus

No, nothing at all to apologise for, don't worry Most people are the same - connect things up and enjoy using them rather than building and modding things. Hopefully your new scaler works well, and that can help others in the same situation.

Good news everyone! This scaler works a treat!

For reference this is the one that works:
https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1

"ELEPHAS Scart to HDMI scaler" it has a toggle from 800x600 through 1024x768 up to 1080p both 50Hz and 60Hz, PAL or NTSC. It can upscale a HDMI input too.

The one that didn't work was this Neoteck one:

https://www.amazon.co.uk/dp/B01KHT1O...ing=UTF8&psc=1

[Jope]

How does the Elephas handle the Amiga's 240p/288p? Does it do a forced deinterlace?

[Geon106]

Originally Posted by Jope

How does the Elephas handle the Amiga's 240p/288p? Does it do a forced deinterlace?

I don't have the Amiga set to interlaced and the scaler seems fine passing it on as 720p/1080p to the TV. I haven't tried changing the Amiga to PAL super hires though

[mark_k]

Originally Posted by Geon106

The one that didn't work was this Neoteck one:

https://www.amazon.co.uk/dp/B01KHT1O...ing=UTF8&psc=1

Are you sure that's the right link? That product converts from HDMI to SCART, so it's not surprising it didn't work the other way around...

[Geon106]

Originally Posted by mark_k

Are you sure that's the right link? That product converts from HDMI to SCART, so it's not surprising it didn't work the other way around...

Ah sorry no. It's this one:

https://www.amazon.co.uk/gp/product/...A11KQ4AB16XUUQ

They both look identical and when copying it here didn't read it lol.

[Jope]

Originally Posted by Geon106

I don't have the Amiga set to interlaced and the scaler seems fine passing it on as 720p/1080p to the TV. I haven't tried changing the Amiga to PAL super hires though

I meant non-interlace, aka progressive. Many of these scalers do not understand progressive PAL or progressive NTSC, instead treating it as interlaced and losing every other frame of information that the computer displays.

[Geon106]

Originally Posted by Jope

I meant non-interlace, aka progressive. Many of these scalers do not understand progressive PAL or progressive NTSC, instead treating it as interlaced and losing every other frame of information that the computer displays.

The TV is reporting it as 1080p rather than 1080i so I assume it's passing through progressive. But I'm not sure how else to check?

[Jope]

This is not possible to deduce by the output mode. The forced deinterlace either happens during conversion or it doesn't.. :-/ Photon made a blinker application that can help, also watching things that get updated every frame can tell you, but this needs a trained eye. :-)

When doing the actual testing, you need to run the tester without a numeric argument, so that it outputs on every frame.

[Geon106]

Originally Posted by Jope

This is not possible to deduce by the output mode. The forced deinterlace either happens during conversion or it doesn't.. :-/ Photon made a blinker application that can help, also watching things that get updated every frame can tell you, but this needs a trained eye. :-)

Hmm. Well ive not really put it through its paces on many games other than to check for latency but will keep an eye out if it feels it's skipping every other frame

[Geon106]

Just seen your attached file. I'll try it out