Cheap SCART cables & TV picture quality

[ColinJ]

A quick and simple way to improve your TV picture quality (If you still use SCART cables)?

Over the years, I have accumulated lots of different SCART cables and they are all cheapo ones. They do the job, but they are not top quality. The main difference between a cheap cable and a more expensive one is that the cheap ones do not have individually screened signal wires inside. As such, they are subject to crosstalk where signals from some wires induce interference in others in the same cable.

I'd noticed this on my TV in the past when watching DVDs. Sometimes I could see a very faint 'ghost' image of what was on whatever channel the TV was tuned into before switching over to the AV input to watch the DVD.

I kept meaning to do something about it, but I don't watch that many DVDs so it didn't bother me that much. Things changed over the past couple of weeks, however, when we underwent the great Digital Switchover here in Hebden Bridge, which was completed last night ...

I tuned my Freeview box into the new set of channels and was disappointed to see that the picture quality was fuzzy and speckly. A digital signal shouldn't be like that - it should either be perfect, or freeze or break up into blocks if there is too much intereference to reception. This was an analogue problem!

It got me thinking about the SCART leads again. Something was causing analogue crosstalk onto the RGB signal wires which brought the signal in to the TV from the Freeview box.

I went online to find the pinout for a SCART connector and discovered that a TV can output a composite video signal on pin 19 of the connector. That would be of whatever the analogue TV tuner was tuned to. Previously, that would have been an analogue TV programme, but now those have all gone. The analogue signal from my TV's internal tuner is now just a lot of fast-moving speckles. These signals were bleeding through onto the RGB input wires in the cable from the composite video output from the TV.

Now, I have absolutely no need for a composite video output from my TV (I'm sure that most of you don't either). I decided that I'd take one of my spare cables and cut the signal wire off pin 19 to see if it made any difference to the TV picture. Bated breath time ...

I plugged the replacement cable in and was gobsmacked at the improvement in picture quality! On BBC1, the picture is now very close to DVD quality. I am super-happy with it. [sup]1[/sup]

Ideally, we would all use expensive high quality SCART cables and wouldn't suffer from this problem in the first place, but my experiment has shown that it might not be necessary. If you suffer from the same kind of interference on your TV picture, try the pin 19 snipping experiment or replace your cables with quality ones with individually screened signal wires.

Note:

1. If you go for the snipping option, unplug the cable first to be on the safe side!
2. You need to mark that end of the cable as the one that goes into the TV, and plug it in that way round!
3. This article gives you more detail. (The red circle in the close-up photo missed the pin slightly but you can see it is the bottom left one, looking at it that way.)

The only complaint I have now is that I've just discovered that we only get 'Freeview Light' here so no ITV3/4, Film4 etc. I'm peeved because I get ITV1/2+1 and 4+1 which are IMHO a waste of channels. Hmph!




[sup]1[/sup]I'm not quite as impressed with some of the other channels though they are still better than my ghosting old analogue picture quality was. A few washed out skin colours here and there, and I noticed blockiness in turbulent water when I was watching triathlon swimming the other night

 

[ian turner]

SCART cable ?
Wassat ?
Is it like HDMI ?

 

[ColinJ]

SCART cable ?
Wassat ?
Is it like HDMI ?

Yeah, kind of like HDMI, only not as good!

Old skool connectivity for people like me with old TVs, VCRs (ugh!), analogue satellite boxes (for pro cycling free on International Eurosport - yay!), old analogue hard disk recorders/DVD players (for recording the free cycling/playing DVDs), Freeview boxes and/or any other kit which uses SCART not HDMI!

 

[2Loose]

Old skool HDMI without HDCP built in. (as well you know!)

 

[xxmimixx]

Apologies if off topic but too tired to read the whole post
but the title reminded me of this article I read not long ago

Don't fall for the HDTV cable con: £2 leads work just as well as £100 ones

 

[ColinJ]

Apologies if off topic but too tired to read the whole post
but the title reminded me of this article I read not long ago

Don't fall for the HDTV cable con: £2 leads work just as well as £100 ones

SCART cables are carrying analogue signals so they are much more susceptible to interference than HDMI cables which are carrying nice robust digital signals.

Cheap HDMI cables may very well be fine whereas cheap SCARTS are not so good, as I have discovered (but worked around).

 

[brockers]

I think you just wanted to tell us how clever you've been !!



Very good though. Love a bit of resourcefulness and intelligent tinkering myself. Now, if only I could work out how to unbrick my flipping internet radio ..

 

[Bman]

Good OP

I used to mess around a lot with scart when TV tuner cards and Svideoout were introduced to the PC market. I made several splitter leads to feed all the different inputs. Audio to the amp, TV to the PC, PC to the tv etc.

All my scart cables were cheap ones. Did the job.

 

[ColinJ]

I think you just wanted to tell us how clever you've been !!

Well, maybe someone with a degree in Electronic Engineering shouldn't take 10 years to fix a simple problem like that ...

 

[brockers]

Well, maybe someone with a degree in Electronic Engineering shouldn't take 10 years to fix a simple problem like that ...

Funny isn't it. In my experience people who have technical qualifications seem to keep older kit running for longer (HiFi, tellies, mobiles etc). "Late-adopters" as the marketing bods call them. Maybe they're not as fazed by something if it breaks down; perhaps it's more important and satisfying to uinderstand why it's gone wrong and to get it working as it should, than to rush out to buy a new one* E.g., many motorbike mechanics I've known run around on mechanically very sound, but cosmetically tatty twenty plus year old bikes. I've got two pairs of speakers that I built from Wilmslow Audio plans. One pair's an LS3/5A copy and the others are near-field studio monitors. They are still amazing bits of kit twenty or so years on and I wouldn't think of getting rid of them.

Back to the TV though. I'm still using a CRT telly with a Freeview box, and the picture had been pants for years. Talk about laziness - it took me about fifteen minutes to sort it by feeding the aerial signal straight to the Freeview, and not through the DVD player. My aerial is rigged up in the loft with line-of sight to the Crystal Palace transmitter and with a mains booster the picture is now so sharp, that I really can't see the point of a flat screen just yet. Though it would be nice to feed downloads from the laptop onto a bigger screen at some stage.

I was wondering though - doesn't cross-talk depend on whether the signal is sent down a waveguide (shielded coaxial) or a bit of solid wire, irrespective of whether it's digital or analogue?

*Or they're skint, which is more likely come to think of it!

 

[ColinJ]

Funny isn't it. In my experience people who have technical qualifications seem to keep older kit running for longer ...

I've known run around on mechanically very sound, but cosmetically tatty twenty plus year old bikes. I've got two pairs of speakers that I built from Wilmslow Audio plans. One pair's an LS3/5A copy and the others are near-field studio monitors. They are still amazing bits of kit twenty or so years on and I wouldn't think of getting rid of them.

Ho ho - I bought my PC in 2000 but only expanded the memory in it last year!

The sound from this computer comes through an old Marantz amplifier that I bought off a colleague in 1987 and the speakers are Mission 77s that I bought from a hifi shop in Manchester when I was a student in 1983! (I do have a slightly more modern 2001 surround sound system for the TV downstairs.)

I was wondering though - doesn't cross-talk depend on whether the signal is sent down a waveguide (shielded coaxial) or a bit of solid wire, irrespective of whether it's digital or analogue?

Digital signals are more tolerant of interference. The receiving circuitry effectively only has to be able to tell the difference between 'on' and 'off' so unless any interference is sufficiently bad to make that amount of difference, it is ignored. Digital cables will still be shielded though.

In one sense, digital signals are still analogue! The same tricks that help protect analogue signals work with digital ones. Audio engineers have been using 'balanced' differential signals for years to cut down on interference problems. Take a look at the pinout for an HDMI connector and what do you see - signals in differential pairs, each pair with its own screen!

The problem I referred to with my cheap SCART cables is that they only have one lot of shielding, for the entire cable. That helps reduce interference getting into the cable from outside, but it doesn't help reduce internal crosstalk from one cable core to another. A good cable would have each signal cable individually screened, and possibly an overall screen too.