RE: SCART grounding

["Keith Doxey" <ukha@xxxxxxxxxxx>]

> Just wondering if anyone has any in depth knowledge of the grounding
> arrangements of scart connectors? (Mr Doxey, I’m guessing!)
>

Hi James, did I hear my name mentioned :-)

> I’m endeavouring to send an RGB signal over cat5.
>
> I have a pair of 4 x composite video passive baluns and have made a
> couple of scart to 4 x phono breakouts for the R/G/B and
composite/sync
> connections.
>
> Within the scart connector there are separate grounds for each signal,
> and that is how I have wired them to the phono connectors.  However,
the
> baluns common all the grounds together (unnecessary I would have
thought
> given the available wires).  Is this likely to be a problem?
>

Not likely to be a problem because they will all be connected together in
both the TV and source device.

> When I have this arrangement connected I get a picture, although it
> appears to be only composite (ie when I pull any of the RGB
connections
> there is no change in quality).
>

Well at least you know know one pair is working. Consumer kit *usually*
sends composite video instead of composite sync.

> Any thoughts much appreciated as aside from the commoning of the
> grounds, this setup should be essentially the same as an RGB wired
> scart-scart cable.
>

Essentially the same but subtley different.

Unless you have a very strange SCART lead there will be another two wires
connected (excluding audio)

PIN 8 - AV Switching. 0V = Tuner, 5V = AV 16:9, 12V = AV 4:3

PIN 16 - Fast Blanking aka RGB. This pin tells the TV that it is an RGB
signal

There seems to be a trend amongst TV manufacturers to ONLY allow an RGB
input to be controlled by the external device.

My old Mitsubishi TV will auto switch given the correct signal on the SCART
pins but will also manually allow the following. 2 SCARTS

AV1 button toggles between AV1 (Composite) and AV1-RGB
AV2 button toggles between AV2 (Composite) and AV2-S

My other TV's behave differently as follows

25" JVC. 2 SCARTS + Side mounted phono/din AV1, AV2 and AV3 all have
individual buttons which select the input. There is also a button marked
"S-IN" which will change that input to S-Video and this is
remembered. AV1
will also accept RGB but ONLY under external control.

14" Bush. Single SCART AV button cycles through Tuner, AV, AV-S. Will
accept
RGB but only under external control

14" Beko. Single SCART. AV button only does Tuner/AV. No S-Video
capability.
RGB only under external control.

Unless you can find a menu option for forcing RGB mode on the SCART you
will
need to provide a swiching voltage to forcibly activate it. You need 5 or
12V into Pin 8 depending on 16:9 or 4:3 aspect ratio and you need to feed
5V
VIA a 100 ohm resistor into Pin 16. You also need to remove the voltages
when not in use as some TV's will display an RGB input just because Pin 16
is active even if Pin 8 isnt. (My Mitsubishi does this)

Of course, you could always use a set of KAT5-RGB which will handle all of
this for you and give you IR control as well :-)

Hope that helps

Keith