Sinclair ZX80 / ZX81 / Z88 Forums

just noticed that RGB != Component.

Not sure if there is any RGB to HDMI converter...

shadow338 wrote:just noticed that RGB != Component.

Not sure if there is any RGB to HDMI converter...

There are two types of RGB SCART to HDMI converters that I know of. I have one and have used it with a QL without problems.
I have SCART TVs that are happy with the video signals from most of my computers, so have not tried with a Harlequin. I would test it, but at the moment the Harlequin and the RGB SCART to HDMI converter are packed away in storage.

This is the type that I have eBay link

Mark

Hi everyone,

PokeMon wrote:
"First C35 (3.3nF) and R49 (2.7k) are removed. These are not needed and it is unclear why the CHROMA signal is connected to the composite sync signal this way and what was the initial purpose."

What was the initial purpose?)
These parts seem to be included in other ZX Spectrum clones too...

e_glu wrote: ↑Sat Oct 17, 2020 8:26 pm "First C35 (3.3nF) and R49 (2.7k) are removed. These are not needed and it is unclear why the CHROMA signal is connected to the composite sync signal this way and what was the initial purpose."

What was the initial purpose?)
These parts seem to be included in other ZX Spectrum clones too...

Can be of course used in other models, anyway it is unclear whatever this connection was used for. It connects Chroma (which is only needed for S-Video outputs together with Luma) with composite sync. Adding these signal is still nonsense in my opinion, Chroma signal can not be used alone (without Luma) and the resistor ratio 2.7k to 270R gives 10% on sync signal. If connected correctly to a normed 75R input in a TV there comes around 3% of Chroma to the sync input which is not interested in Chroma signals.

If anybody can explain the reason, please. For me this is maybe just copied from another application (partly) without understanding it.
Or it is just another hat trick from Clive, which is never explored.
I use it in my Harlequin without these components to add a S-Video Output as well. Not as good as RGB but better than just a composite signal.

shadow338 wrote: ↑Sat May 07, 2016 6:26 pm thanks PokeMon, I will probably try one of your mods.

My goal is to move away from s-video in favor to HDMI, so I will try your RGB mode and then use a converter from RGB (component) to HDMI.

Hopefully it will work.

You can use this adapter to convert RGB to HDMI

https://www.amazon.com/Genesis-Original ... 130&sr=8-3

Here is how it look like

https://www.youtube.com/watch?v=mseCgogCOqs

PokeMon wrote: ↑Sun Oct 18, 2020 6:27 pm If anybody can explain the reason, please. For me this is maybe just copied from another application (partly) without understanding it.
Or it is just another hat trick from Clive, which is never explored.
I use it in my Harlequin without these components to add a S-Video Output as well. Not as good as RGB but better than just a composite signal.

This resistor and capacitor add by Ingo from Germany, he said it help to make picture be in the middle of screen.

superfo wrote: ↑Wed Nov 25, 2020 9:05 pm This resistor and capacitor add by Ingo from Germany, he said it help to make picture be in the middle of screen.

Okay thanks.
But for me it is more Voodoo. The chip supports either composite video and s-video, so s-video output is wasted. Okay is no official connector for the signal aboard but s-video has better quality. Just in case.

Hello everybody!

I can’t help but thinking that the original intention was to provide two possibilities for RGB syncing: either CSYNC, or LUMA signals (and the PCB has a mistake connecting that trace to CHROMA), but not both at the same time!

dac wrote: ↑Thu Jul 08, 2021 9:13 am Hello everybody!

I can’t help but thinking that the original intention was to provide two possibilities for RGB syncing: either CSYNC, or LUMA signals (and the PCB has a mistake connecting that trace to CHROMA), but not both at the same time!

Hello

I’m not sure having a choice as you suggest is actually much of a choice. Q1 only carries a composite sync (CSYNC) signal and this is the only sync signal fed to U48. All RGB SCART TVs should operate without problems using a composite sync signal. As will most RGB monitors (that accept a 50Hz video signal).

The LUMA signal is monochrome video with the composite sync signal included. I can’t see any reason why a RGB monitor or TV using RGB SCART would need to have the luminance part of the signal. Unless it was intended to be used as a monochrome composite video signal for monochrome monitors. But given that the board is supposed to be compatible with the ZX Spectrum computer, which is a computer specifically designed to produce a colour video picture, I think that idea is unlikely.

Mark

Well, there might be some timing difference between CSYNC and LUMA sync, therefore some different horizontal alignment between those 2 cases (one might work better than the other with different displays).

I used to sync SCART RGB with composite video, but doing so, the chrominance subcarrier (4.433 MHz) somehow managed to interfere with RGB image; syncing with CSYNC (or perhaps LUMA?) is free from this artefact.