Edjucate Me: +5v and RGB cables

[SuperDeadite]

What is the actual purpose in having a +5v line as part of an RGB cable?
I've heard, that the +5v tells the TV that the cable carries an RGB signal.
Correct? Which makes sense for PAL territories as SCARTs have been used to carry
RGB, S-Video, and Composite.

But here in Japan, 21pin RGB is a bit different. The 21pin connector was never
used to carry anything but RGB. I'm wondering if a +5v line on a Japanese RGB
connection has any purpose (besides powering an extra device, like a JROK box).

For example, my TV is a Sony Trinitron. They accept RGB or Component through
Sony AV-Multi (Playstation plug). And they must be manually set to RGB or Component via the remote.

The PS2 for example can output in RGB or Component, and if you want to switch to the other,
you must change the setting in both the PS2 and the TV manually.

My XRGB2+ works the same way, it will take RGB or Component through the 21pin,
but you have to manually switch it. No way to auto switch.

I've just modded my PC-Engine SuperGrafx for RGB. My current test cable does not have a +5v line.
I'm only using RGBS,Ground, Sound. Picture is beautiful on both the TV and the XRGB2+.
Is there any point to adding a +5v line to my final finished cable?

EDIT: LOL I can't spell worth shit

 

[rcantor77]

Here in the UK the +5v is used to change the Status & Aspect Ratio through Pin 8:

* 0–0.4V → off
* 5–8V → 16:9
* 9.5–12V → on/4:3

A resistor is then connected from Pin 8 to Pin 16 inside the Scart socket:

Blanking signal up
RGB-selection voltage up

* 0–0.4V → composite
* 1–3V → RGB

So in answer to your question, it is not just to tell the TV that it is an RGB signal, it also changes the aspect ratio.

 

[jew90]

Erm..

Japanese 'SCART' connector VS UK connector pinout.

5v goes to the YS In

Special Notes:

■Audio Input: 0.40 mVrms, > 47K ohms
■Audio Output: 0.40 mVrms, > 10K ohms
■CVBS (Composite Video) in and out: 1 Vp-p, 75 ohms, sync: negative
■Ym Input: Switches RGB to half-brightness, for video overlay (L: < 0.4V, H: > 1V, 75 ohms)
■Ys Input: RGB in/out: (Ground for output, 1V+ for Input (preferred)1))
■All RGB lines: 0.7 Vp-p, 75 ohms

--------------------------------------------------------------------------------

YS Input seems to Set up RGB In / Out... 1v+ for Input.. which is what you'd want?

 

[jew90]

Here in the UK the +5v is used to change the Status & Aspect Ratio through Pin 8:

* 0–0.4V → off
* 5–8V → 16:9
* 9.5–12V → on/4:3

A resistor is then connected from Pin 8 to Pin 16 inside the Scart socket:

Blanking signal up
RGB-selection voltage up

* 0–0.4V → composite
* 1–3V → RGB

So in answer to your question, it is not just to tell the TV that it is an RGB signal, it also changes the aspect ratio.

You don't need to connect pin 8 to pin 16 unless you want the same voltage on both. For example, you might want 3v on Pin 16 (RGB select) and 12v on Pin 8 (4:3 aspect ratio / autoswitch)

Or you might not connect anything to Pin 8, in this case you'll need to manually switch to the AV channel that the scart is plugged into and set up the correct aspect ratio.

Of course none of this applies to the Japanese RGB21 port..

 

[FusionITR]

I have such distain for the SCART cable. Too bad it was the only thing standardized to carry RGB video during the 16 bit era.

 

[jew90]

I have such distain for the SCART cable. Too bad it was the only thing standardized to carry RGB video during the 16 bit era.

Whats wrong with the scart cable?

 

[FusionITR]

Whats wrong with the scart cable?

Big and bulky, does not easily connect and disconnect due to fitment problems (often have to jiggle it in and out), 21 pins are overkill for a A/V interconnect and worse of all, the end of the connector is angled.

 

[Hewitson]

I'd agree with most of that however its still far better than the shitty RCA connectors your country designed :P

 

[Kyuusaku]

Hmm, I think only RCA connectors should have been standard until HDMI.

RGB (sync on green) would have been great over 3x RCA like component.

 

[Hewitson]

It would have. Why they didn't chose to do it that way is beyond me.

 

[jew90]

Big and bulky, does not easily connect and disconnect due to fitment problems (often have to jiggle it in and out), 21 pins are overkill for a A/V interconnect and worse of all, the end of the connector is angled.

There not that bad! & There not all angled...

Some of the fully wired scart leads are quite bulky but there mainly used to connect tv's to videos / dvd etc so are not removed very often. most of the console RGB scart leads are tiny and easy to use.

The number of pins are so they are bi-directional.. you have audio / rgb/ composite and all the ground pins (seperate grounds for rgb lines) for input AND output, plus a couple of extra pins for tv / image control.

Dont forget the RGB was originally made to be overlayed over the compostie image in the form of subtitles from a closed captioning box which is why there are a lot of pins.

Oh and since you can only plug it in one way you can fiddle around the back of the TV without moving it out as it will only fit one way.. unlike RCA's that you can mix up...