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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: Snowwie on February 18, 2012, 11:51:58 PM

Title: See 'squares' on my LG LCD monitor
Post by: Snowwie on February 18, 2012, 11:51:58 PM

I have recently bought a (second hand) LG TV/Monitor type M1917A.
Click this link (http://i43.tinypic.com/1ewhs4.jpg) to see my setup.

This monitor has a SCART input, which I use for my Amiga 1200.

I use a normal RGB->Scart cable, but I notice faint squares on screen. Also, when showing a black screen I see some interference.

Is this due to lack of cable quality? Or is just the low 15Khz output of the Amiga and the relative big size of the screen (19") which creates this effect?

Title: Re: See 'squares' on my LG LCD monitor
Post by: gertsy on February 19, 2012, 12:55:35 AM

Hi Snowwie. Welcome to AORG.
Could be the cable or the circuitry.  I doubt the cable has a ferrite core on it?  You can buy clip on ferrite cores at electronic components stores, that might help.  It does sound like RF interference?  Might even be coming from your A1200 RF Module especially if it has the shielding cover removed.
Other problems could be loose shielding connections, corrosion or degredation in the cable.  Especially if its old.
It could also be a lack of signal earth on the cable.  RGB likes a separate earth for each signal RG&B.
Alternatively but unlikely the pinouts might not be optimum.  Check the amiga manual pinouts to the monitor's scart and ensure the correct pins are in use.  As it is a standard it is unlikely that they are not correct.
Finally It could just be the quality of the monitor circuitry.  That's less noticable from a standard scart video component.  
If it was my setup i'd be re-wiring the cable with new high quality video cable, separate signal earths and adding a ferrite core (maybe 2, 1 at each end).

BTW your setup looks great.

Title: Re: See 'squares' on my LG LCD monitor
Post by: kickstart on February 19, 2012, 02:20:27 AM

If you have some electronics skills you can compare your cable with the following scheme and maybe fix it for a nice output

http://www.ianstedman.co.uk/Amiga/amiga_hacks/Amiga_SCART/amiga_scart.html

Title: Re: See 'squares' on my LG LCD monitor
Post by: Snowwie on February 19, 2012, 02:42:00 AM

I suspected it could be the cable, because I have seen that scheme before and the connections in my cable are different.

Now I do have to make the decision whether to solder the cable to correct specs, and buying 3 kinds of resistors + adding transport costs, or, just buying a new one from Amigakit. I am not sure those have ferrite cores, but neither about the cable I already have.