English Amiga Board - View Single Post

Boot_WB · 08 September 2009, 12:50

@Stedy

Good comprehensive guide!

I have the following comments/observations:

I have no resistance between 10 (Amiga) and 20 (SCART) and have had no ill effects (thus far).

Also, I have nothing connected to pin 18 of the SCART with no ill effects.

As with yourself, I used a similar (80 Ohm) resistance between pin 23 (Amiga) and 16 (SCART), although I'd recommend testing the resistance under load for any particular TV between pin 16 and ground on the SCART socket to obtain the correct resistance to insert between 23 (Amiga) - 16 (SCART).

The resistor you solder in between +5V out on the RGB port, and pin16 of the SCART should be NO LESS THAN 0.7 x measured resistance measured between pin16 - ground, and no greater than 2.5 x measured resistance to achieve the 1.4V - 3V required by the RGB sense circuit on pin 16.

Additionally, your colour grounds for blue and red appear to be crossed: Should be (Amiga - SCART): 16-13, 17-9, 18-5, although this shouldn't make the slightest difference as colour grounds tend to be common, or have identical term resistance in my experience.

I guess from the 1K resistance between 22 (Amiga) - 8 (SCART) that pin 8 of SCART has a high resistance termination?

One final point to note - audio in/out and video in/out are always crossed on SCART cables (in my experience). Audio/video output at end #1 of a SCART-SCART cable will always connect to video in at end #2 for obvious reasons. Fooled me the first time I made my cable up though...

Excellent presentation, and really good info on the effects of changing/removing connections - should help a lot of people in troubleshooting their homebrew cables! :-)

08 September 2009, 12:50	#3
Boot_WB Novice in the Black Arts Join Date: Nov 2004 Location: Kingston upon Hull Age: 47 Posts: 263	@Stedy Good comprehensive guide! I have the following comments/observations: I have no resistance between 10 (Amiga) and 20 (SCART) and have had no ill effects (thus far). Also, I have nothing connected to pin 18 of the SCART with no ill effects. As with yourself, I used a similar (80 Ohm) resistance between pin 23 (Amiga) and 16 (SCART), although I'd recommend testing the resistance under load for any particular TV between pin 16 and ground on the SCART socket to obtain the correct resistance to insert between 23 (Amiga) - 16 (SCART). The resistor you solder in between +5V out on the RGB port, and pin16 of the SCART should be NO LESS THAN 0.7 x measured resistance measured between pin16 - ground, and no greater than 2.5 x measured resistance to achieve the 1.4V - 3V required by the RGB sense circuit on pin 16. Additionally, your colour grounds for blue and red appear to be crossed: Should be (Amiga - SCART): 16-13, 17-9, 18-5, although this shouldn't make the slightest difference as colour grounds tend to be common, or have identical term resistance in my experience. I guess from the 1K resistance between 22 (Amiga) - 8 (SCART) that pin 8 of SCART has a high resistance termination? One final point to note - audio in/out and video in/out are always crossed on SCART cables (in my experience). Audio/video output at end #1 of a SCART-SCART cable will always connect to video in at end #2 for obvious reasons. Fooled me the first time I made my cable up though... Excellent presentation, and really good info on the effects of changing/removing connections - should help a lot of people in troubleshooting their homebrew cables! :-)