Someone has good advice - I've improved since and I finally did get a pot of proper flux that I use all the time now.
Still hate soldering DIN plugs though.
More progress today.
Made a new DIN-to-DB9 cable. More stable image but shifted to the right. Strapping the H_SYNC or V_SYNC invert pins shifts the image left but flickers more.
Colours are still wrong though - Ewan pointed out this was because green was missing.
The C128D shows a perfect image but also incorrect colours. This is using a different cable so the green must be missing somewhere internally ... although, maybe I should also check the VGA cable I'm using.
Still hate soldering DIN plugs though.
More progress today.
Made a new DIN-to-DB9 cable. More stable image but shifted to the right. Strapping the H_SYNC or V_SYNC invert pins shifts the image left but flickers more.
Colours are still wrong though - Ewan pointed out this was because green was missing.
The C128D shows a perfect image but also incorrect colours. This is using a different cable so the green must be missing somewhere internally ... although, maybe I should also check the VGA cable I'm using.