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CPC464 and SCART again

Started by orange, 09:13, 28 April 10

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orange

i connected pin 6 to 20 and then pin 4 to 16. it worked with one small problem; the (panasonic) tv would occasionally 'detect' again that its rgb (and not composite) and it would display 'RGB' in corner for a sec.
probably because there's not enough voltage on SCARTpin16? it was a bit annoying, so I connected +5V to 220ohms and then scart pin 16 (I left CPC pin 4 unconnected) and it works better.

if I understood correctly we can connect either pin 4 (SYNC) or pin 6 (LUM) from CPC to pin 20 on SCART? but what about SCART pin16, is there a way to make it work without the need for +5V? (would it perhaps work with 6->16 ?)

arnoldemu

Quote from: orange on 09:13, 28 April 10
i connected pin 6 to 20 and then pin 4 to 16. it worked with one small problem; the (panasonic) tv would occasionally 'detect' again that its rgb (and not composite) and it would display 'RGB' in corner for a sec.
probably because there's not enough voltage on SCARTpin16? it was a bit annoying, so I connected +5V to 220ohms and then scart pin 16 (I left CPC pin 4 unconnected) and it works better.

if I understood correctly we can connect either pin 4 (SYNC) or pin 6 (LUM) from CPC to pin 20 on SCART? but what about SCART pin16, is there a way to make it work without the need for +5V? (would it perhaps work with 6->16 ?)
LUM is only required for green monitor.
My games. My Games
My website with coding examples: Unofficial Amstrad WWW Resource

nocash

What are you doing exactly?
Did you see http://cpcwiki.eu/index.php/TV_SCART_cable ?
Are you using the same connection, but still get problems?

Of course, the batteries in above schematics aren't that optimal. Using a resistor to 5V to produce 1V-3V would be better than batteries. But it with different TVs you may need different resistors. Maybe best would be using two 1K Ohm resistors:
  GND ------1K-------x------1K------5V
In the middle (x) you should get perfect 2.5V. And even if the TV drags it down a little, you should still be in the 1V-3V range. Btw. you don't have a multimeter to verify what voltage you have, or do you?

Bryce

Have you tried the battery-less alternative pinout shown here: http://www.cpcwiki.eu/index.php/TV_SCART_cable
that works on most modern TVs.

Bryce.

eto

Quote from: Bryce on 10:44, 28 April 10that works on most modern TVs.

I have 2 LCD TVs here. For one it works perfectly fine, the other now shows a perfect colour image but at the same time a grey scale ghost image, a few centimetres shifted to the right. That's probably due to the luminance being fed into pin20 I guess. Would there be another option like feeding sync into 20 and luminance into 16 with that capacitor or would that not work?

Bryce

I haven't tried, give it a go?

Bryce.

eto

Quote from: Bryce on 11:27, 12 February 22
I haven't tried, give it a go?

Bryce.

OK, so nothing obvious that could do any harm, right? then I will try and let you know.

Bryce

No, my guess is that you will get a flickering picture as if the sync signal was too low.

Bryce.

eto

Quote from: Bryce on 11:54, 12 February 22No, my guess is that you will get a flickering picture as if the sync signal was too low.

no flickering, but it also doesn't switch to RGB automatically.

btw: I only had a 10V capacitor. Will that be sufficient? In the original thread you mentioned 16V but on the Wiki page it only says 100µf but nothing about the voltage.

Bryce

10V is fine. I wrote 16V because that's usually the standard value you find most often.

Bryce.

eto

Quote from: Bryce on 09:33, 14 February 22Bryce.


So, I do now have a second LCD with a greyscale ghost image. Seems this could be a pattern for cheap, small "camping" LCD TVs. Would it make sense to add a note to the WIKI article, that this can happen with the battery-less alternative?

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