Composite to S-video lead.

Discussions about Sinclair ZX80 and ZX81 Hardware
Post Reply
Moggy
Posts: 3231
Joined: Wed Jun 18, 2008 2:00 pm

Composite to S-video lead.

Post by Moggy »

Not being in possession of any of Karl's wonderful video boards thanks to Lardo buying up the entire European stock (Only joking Lardo :lol: ) I did the simple transistor mod. The zeddy in question doesn't have the back porch ULA fitted so whilst I get a good picture it was of the expected darkness that even full brightness adjustment doesn't really cure.

I had in my box of bits a composite to S-video lead and as the portable TV I use has an S-video socket I tried the lead just to see what, if any, effect it would have. I was surprised to see that not only did it work but the brightness was at the same level as a back porch ULA with no brightness/contrast adjustment needed.

My question, just as a curiosity is, why does a normal composite connection give the expected dark picture given the lack of back porch but when connected to S-video via the conversion lead gives a display equal to a back porch ULA?

Do any of the gurus think this would work on any TV set or did I just drop lucky with my cheap LCD 14" portable?
User avatar
1024MAK
Posts: 5101
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: Composite to S-video lead.

Post by 1024MAK »

S-video is just the monochrome composite video with a separate channel for the encoded colour component.

It’s hard to say if the behaviour you’ve seen is typical or not. I’ll have to try this with some of my kit.

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: Standby alert :!:
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer later in the year.
Moggy
Posts: 3231
Joined: Wed Jun 18, 2008 2:00 pm

Re: Composite to S-video lead.

Post by Moggy »

Thanks for that Mark.

Just for reference (not that it should make any difference)

Issue three board

184 ULA

simple transistor mod

14" LCD TV under the Wharfedale brand though nothing to do with the well known speaker manufacturer according to Mrs Moggy who worked for them, so cheap knock off.

EDIT.

Wharfedale is Argos own brand apparently.
User avatar
1024MAK
Posts: 5101
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: Composite to S-video lead.

Post by 1024MAK »

Moggy wrote: Sun May 22, 2022 1:52 pm 14" LCD TV under the Wharfedale brand though nothing to do with the well known speaker manufacturer according to Mrs Moggy who worked for them, so cheap knock off.

EDIT.

Wharfedale is Argos own brand apparently.
For as long as I’ve been an adult, ‘badged’ (branded) TVs have been a thing. Yes, this included CRT colour TVs. Whereby the name/badge/brand on the outside has no bearing on the actual manufacturer of the electronics on the inside…

That’s why the list of codes for replacement programmable remote controls is such a long list. If you are really bored, you can play snap as you noice the same code(s) shared across different brands…

Some of the own brands change name over time. Especially as Argos itself is effectively a brand, it now being part of Sainsbury’s…

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: Standby alert :!:
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer later in the year.
Post Reply