Diagonal Lines on TV

[eva]

Hello!

I have this strange issue with some diagonal lines going from the bottom-left of the screen and roughly towards the top-right of the screen on my A1200. They move around a bit but I cannot influence it - for example, if I open a large drawer, the lines do not change (not faster or anything). These lines are just there and move from bottom-left of the screen towards the top-right of the screen regardless what I'm doing...

This happens on Workbench or in games on both the RCA output and SCART. I have no VGA addon so I cannot check if VGA would be the same. I have not tried aerial though...

Is there an explanation for this? Is there something I can do?

It doesn't bother me much but after searching the forums I have not seen something similar so I thought to ask, perhaps some Guru around here has a clue what this is... I have attached a picture taken through the RCA output and highlighted the "lines"... It is out of a game but the same happens in Workbench.

Thanks!

[pandy71]

Originally Posted by eva

Hello!

I have this strange issue with some diagonal lines going from the bottom-left of the screen and roughly towards the top-right of the screen on my A1200. They move around a bit but I cannot influence it - for example, if I open a large drawer, the lines do not change (not faster or anything). These lines are just there and move from bottom-left of the screen towards the top-right of the screen regardless what I'm doing...

This happens on Workbench or in games on both the RCA output and SCART. I have no VGA addon so I cannot check if VGA would be the same. I have not tried aerial though...

Is there an explanation for this? Is there something I can do?

It doesn't bother me much but after searching the forums I have not seen something similar so I thought to ask, perhaps some Guru around here has a clue what this is... I have attached a picture taken through the RCA output and highlighted the "lines"... It is out of a game but the same happens in Workbench.

Thanks!

Disconnect all inputs except Amiga also aerial cable. If there is improvment then i have one idea.

[eva]

Originally Posted by pandy71

Disconnect all inputs except Amiga also aerial cable. If there is improvment then i have one idea.

Hi! I have tried that but no dice. I have also tried disconnecting the fans I have. I cannot find anything that changes the intensity of the lines. Sometimes there's more of them, sometimes less...

This happens for all outputs, RCA and the Amiga port through SCART. It's true that I have not tested on a different TV yet.

[john1979]

It looks like electrical interference, I get similar lines if my PC is plugged into the same power strip as my Amiga, unplugging it makes the lines disappear.

Two suggestions::
Try unplugging the power from various devices near your Amiga
Try attaching an aerial cable between your RF mod and TV, this can really help with cleaning up background noise from the audio and a little with picture noise too. I am assuming it helps the grounding in someway.

[wolfchild]

That interference looks like crosstalk from another video input source on the TV. I do get it on my CRT TV when multiple inputs are active.

The ghost could be originating from the TV tuner input or from one of the other AV inputs. Did you try to unplug or switch on/off other equipment attached?

Ed

[eva]

Thanks! You solved the mystery. It is indeed a crosstalk issue. I have one of those "home boxes" that delivers TV and has an extra SCART input. I was using that SCART input and the "home box" to switch between the TV and the Amiga. If I plug the Amiga SCART cable directly into the TV the lines go away. Now I'm wondering if it's the "home box" or if it's the SCART cable that goes from the "home box" to the TV.

Too bad you cannot give "reputation" on this forum. ;-)

[wolfchild]

Hi! Glad to help!

I'd bet it's the home box unit that causes the crosstalk between its video signal and the Amiga's. I guess it's some kind of TV / satellite or cable decoder?

If your TV has unused phono inputs could you connect directly to them? The cables are quite common and everyone seems to have a couple of pairs lying around. (The ones with red, white and yellow phono plugs.)

Ed

[pandy71]

Originally Posted by eva

Thanks! You solved the mystery. It is indeed a crosstalk issue. I have one of those "home boxes" that delivers TV and has an extra SCART input. I was using that SCART input and the "home box" to switch between the TV and the Amiga. If I plug the Amiga SCART cable directly into the TV the lines go away. Now I'm wondering if it's the "home box" or if it's the SCART cable that goes from the "home box" to the TV.

Too bad you cannot give "reputation" on this forum. ;-)

Originally Posted by eva

Hi! I have tried that but no dice. I have also tried disconnecting the fans I have. I cannot find anything that changes the intensity of the lines. Sometimes there's more of them, sometimes less...

This happens for all outputs, RCA and the Amiga port through SCART. It's true that I have not tested on a different TV yet.

That's why i ask You to disconnect everything except Amiga from TV... classical example of GIGO.
And yes - crosstalk from semiconductor switch is usually high (unless you going for special topologies like T) especially when voltages are out of nominal range (common case in Amiga).