Harlequin video modifications

A place to discuss the ZX80's and ZX81's younger brother - the Sinclair ZX Spectrum
shadow338
Posts: 10
Joined: Tue Mar 29, 2016 7:56 pm

Re: Harlequin video modifications

Post by shadow338 »

just noticed that RGB != Component.

Not sure if there is any RGB to HDMI converter...
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1024MAK
Posts: 3163
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: Harlequin video modifications

Post by 1024MAK »

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
e_glu
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Joined: Sat Oct 17, 2020 2:48 pm

Re: Harlequin video modifications

Post by e_glu »

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...
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PokeMon
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Joined: Sat Sep 17, 2011 6:48 pm

Re: Harlequin video modifications

Post by PokeMon »

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...
Bildschirmfoto 2020-10-18 um 18.19.21.png
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. :shock:
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.
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