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Old 25 May 2009, 17:38   #1
Rabbit80
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SCART issue

Is there a definitive diagram of how a RGB-SCART cable should be wired? My TV is very fussy - I think it expects all grounds to be wired correctly, all voltages to be correct etc! Its that fussy that I can crash it using a composite cable!
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Old 25 May 2009, 17:52   #2
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i have never come across this problem with amiga rgb to scart leads on my tv`s, 20yr tatung, few yr old sony trinitron
i have straight wired leads, part wired leads + a resistor or 2, and fully wired , and they work out the box,
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Old 25 May 2009, 18:01   #3
Rabbit80
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I just bought a cable - and it doesn't work on my LCD - it does auto switch to SCART, but I have no picture!
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Old 25 May 2009, 18:06   #4
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Check the voltage between ground and pin 16 (RGB select) and pin 14 (GND).

Pin 14 should be gnd and pin 16 should be +1v to +3v.

If pin 14 is unconnected or floating you'll need to tie it to ground with a small section of wire.
If pin 16 is unconnected or floating you'll need to wire it to the Amiga's +5v (via an appropriate resistor to bias the voltage).

Make sure LCD supports RGB via SCART.
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Old 25 May 2009, 18:21   #5
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LCD works fine on RGB from digi-box!

Pin 16 has a resistor on it colours look like red red yellow red. I have wired pin 14 to 17 on SCART to add ground to 14.

I have no meter at the moment since i left it at a customers in Sheffield
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Old 25 May 2009, 18:46   #6
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Tested on CRT TV and it works fine - just not on LCD
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Old 25 May 2009, 21:24   #7
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Quote:
Originally Posted by Rabbit80 View Post
LCD works fine on RGB from digi-box!
You sure it is RGB? The main difference between Amiga SCART cable and digi-box SCART cable is pin 20.

With digi-box pin 20 will have composite video.
With Amiga pin 20 will have composite sync.

Result is that digi-box will produce a picture when connected to non RGB capable SCART socket. Amiga will not. As a test you may be able to connect pin 11 (green) to pin 20 (I think amiga has SOG) instead of composite sync, if that gets a B&W picture you know your SCART socket is not RGB capable.

If the LCD can do RGB and pin 16 has the right voltages on the only thing I can suggest is that LCD will not accept non-interlaced signal. Try another console which has RGB and non interlaced signal (Megadrive, SNES, PSOne etc.)

Amiga RGB signal levels are reportedly over voltage, you might need to add resistors to each of the colour inputs (if they do not have them already).

Last edited by alexh; 25 May 2009 at 21:29.
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Old 25 May 2009, 22:05   #8
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@Rabbit80,
See this post from girv:
http://eab.abime.net/showpost.php?p=492721&postcount=11

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Old 25 May 2009, 22:56   #9
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Hardly a definitive wiring. Not all grounds are connected and those that are connected are miss-wired. (although it probably doesn't matter)
Quote:
Originally Posted by Girv
SCART -> Amiga 23 pin
18 -> 17
Composite video SCART input ground (aka SCART pin 20 ground) -> Analog GREEN gnd (aka SCART Pin 9 ground)??

Quote:
Originally Posted by Girv
SCART -> Amiga 23 pin
17 -> 19
Ground for Composite video SCART output (aka SCART pin 19 ground) -> Ground for Composite SYNC Amiga output (aka SCART pin 20 ground)????

Whoever wired this cable up either knows something we don't or they "guessed" the gnd wiring. To be honest, for CRT TV's, it doesn't really matter about all gnds to be connected.

@Rabbit80
Probably a good idea to check SCART pin 18 and see if that is connected to GND though and possibly all the other gnds.

SCART pinout
Amiga video pinout

Last edited by alexh; 25 May 2009 at 23:19.
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Old 25 May 2009, 23:01   #10
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However, it works with an LCD TV, which is what Rabbit has.
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Old 25 May 2009, 23:11   #11
Rabbit80
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Its a job for tomorrow now - i need better light for soldering work!
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Old 25 May 2009, 23:19   #12
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Quote:
Originally Posted by Rabbit80 View Post
I need better light for soldering work!
So it's not just me then!
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Old 25 May 2009, 23:19   #13
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Quote:
Originally Posted by alexh View Post
You sure it is RGB? The main difference between Amiga SCART cable and digi-box SCART cable is pin 20.

With digi-box pin 20 will have composite video.
With Amiga pin 20 will have composite sync.

Result is that digi-box will produce a picture when connected to non RGB capable SCART socket. Amiga will not. As a test you may be able to connect pin 11 (green) to pin 20 (I think amiga has SOG) instead of composite sync, if that gets a B&W picture you know your SCART socket is not RGB capable.

If the LCD can do RGB and pin 16 has the right voltages on the only thing I can suggest is that LCD will not accept non-interlaced signal. Try another console which has RGB and non interlaced signal (Megadrive, SNES, PSOne etc.)

Amiga RGB signal levels are reportedly over voltage, you might need to add resistors to each of the colour inputs (if they do not have them already).
On digi-box I can choose between RGB, CVBS or S-Video... Settings other than RGB look poor and dull. I also had a non-RGB cable for it which would not work on RGB settings, This suggests RGB is fine!

I don't have any other consoles i can test it with. Would it be worth testing WB in an interlaced mode?

I can add resistors to the RGB lines - what values do I need?

Could I wire the amiga RGB to the component input on my TV?
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Old 25 May 2009, 23:21   #14
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Quote:
Originally Posted by prowler View Post
However, it works with an LCD TV, which is what Rabbit has.
It works with Girv's LCD TV. I don't think you can say "this is the SCART wiring for LCD TV's" for a cable which is not fully/correctly populated.

I would be interested to know if Rabbit80 ever gets his working and what was the problem.

I bet money it is the wrong voltage on pin 16

Quote:
Originally Posted by Rabbit80 View Post
I can add resistors to the RGB lines - what values do I need?
Dunno off the top of my head. It's worth checking the voltage on PIN16 first, then all the video grounds particular composite video gnd.

Quote:
Originally Posted by Rabbit80 View Post
Could I wire the amiga RGB to the component input on my TV?
Not without an expensive RGB->YPbPr converter.

Last edited by alexh; 25 May 2009 at 23:30.
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Old 25 May 2009, 23:29   #15
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Which pin is ground for 16? Could I wire a 1.5v battery up to test that theory?

Do all the grounds go to common ground? Which pins SCART side require a ground?
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Old 25 May 2009, 23:32   #16
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SCART Pin 16 has a corresponding ground of SCART pin 14. I wouldn't try a battery myself but you go for it

Quote:
Originally Posted by Rabbit80 View Post
Do all the grounds go to common ground?
Dunno. I've always wired mine upto one gnd so you can use cheaper cable with fewer cores in it. Just used lots of little "U" shapes of wire to "loop" all the grounds together in the SCART plug. But I was always connecting to a CRT TV.

Quote:
Originally Posted by Rabbit80 View Post
Which pins SCART side require a ground?
Dunno. From the multitude of wiring diagrams out there with no gnds I guess traditionally CRT TV's usually only needed one, pin 21 (the shroud). Who knows what LCD's require / expect.

Last edited by alexh; 25 May 2009 at 23:43.
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Old 25 May 2009, 23:39   #17
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OK - so which pins will blow up my amiga or TV if I wire them to ground?
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Old 25 May 2009, 23:43   #18
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If you accidentally wire any of the +voltage signals to gnd you will get magic smoke. Just make sure you do not make any mistakes.

RTFM :

SCART pinout
Amiga video pinout

There is an obvious 1:1 wiring for most grounds.

BUT: you want to check the voltage on PIN16 first. Check the resistor value, see if it is wired to Amiga PIN 22 (+12V) or Amiga PIN 23 (+5V)

If that doesn't work test each gnd one at a time, adding missing ones, starting at SCART PIN 21, SCART PIN 14, SCART PIN 18, then SCART PINS 9, 5 & 13.

If that still doesn't work... perhaps we look at putting resistors on RGB.

Last edited by alexh; 25 May 2009 at 23:53.
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Old 25 May 2009, 23:53   #19
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Thanks - I will try this tomorrow - starting with a 1.5v battery since I have no meter at the moment!
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Old 26 May 2009, 15:43   #20
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Have you solved the problem?


SCART ISSUE that I wish you saw
Sarcastic mister know it all
Close your eyes and Ill kiss you cause
With the birds Ill share
With the birds Ill share
This lonely view
With the birds Ill share
This lonely view
Push me up against the wall
Young kentucky girl in a push-up bra
Fallin all over myself
To lick your heart and taste your health cause
With the birds Ill share
This lonely view...
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