Transientmotion

Hi, I've got a sammichSID that I built about 10 years ago and it used to work fine. I've come to use it again and whilst it boots up properly, the display isn't working fully. The backlight works fine, and can adjust the brightness but no characters display on the screen. I know its probably soldier joints that need redoing, but I'd rather not redo the entire thing if its just one or two that have failed. Any suggestions as to which points to look at? Thanks for your help