HDMI Backporch Mod - Odd Behaviour

[davyrobertson]

So I fitted a back-porch mod to my 81 - all good and when its all plugged in with 1K - the picture is clear and stable. I'm using AV/SV/Scart to HDMI scaler.

Now when I plug in the 16K RAM pack - this is an original one - the picture becomes intermittently unstable. Best way. It jumps for maybe 1/2 second then comes back - its not time based - maybe every 15 seconds or so. If you remove the 16K RAM - totally steady.

I've have the original 12V power supply and a new one which delivers a nice steady 9V @ 1.5A - both so exactly the same. 1K good - 16K jumpy

Anyone come across this ?

[1024MAK]

Did you know that the Sinclair 16K RAM pack contains a DC/DC converter. The switching frequency from this may be upsetting the AV/SV/Scart to HDMI scaler that you are using. Although I can’t work out why it’s 15 seconds...

I can’t think of anything else. Note this is more of a guess than experiencing anything similar myself.

Suggestions: try a different RAM pack,
Try using a TV/monitor that has a composite video input.

Mark

[mrtinb]

I have not have any good luck with these Composite to HDMI Converters. I've settled for an RGBtoHDMI. That's the best result I've got.

[Moggy]

I too have no luck with these HDMI converters (picture constantly blanking). The best I could manage was a composite to VGA converter which would only work satisfactorily with a Zeddy that was encased in an all metal external key board. All my plain Zeddies would cause flickering of the letters/graphics which leads me to think that the metal cased keyboard was somehow shielding the converter from spurious signal spikes.

Now I just look out for those cheap 15" LCD TVs with composite inputs as I'm finding that modern monitors are just too picky in what they will accept signal wise, plus most don't have the composite input.